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   1  =head1 NAME
   2  
   3  Config - access Perl configuration information
   4  
   5  =head1 SYNOPSIS
   6  
   7      use Config;
   8      if ($Config{usethreads}) {
   9      print "has thread support\n"
  10      } 
  11  
  12      use Config qw(myconfig config_sh config_vars config_re);
  13  
  14      print myconfig();
  15  
  16      print config_sh();
  17  
  18      print config_re();
  19  
  20      config_vars(qw(osname archname));
  21  
  22  
  23  =head1 DESCRIPTION
  24  
  25  The Config module contains all the information that was available to
  26  the C<Configure> program at Perl build time (over 900 values).
  27  
  28  Shell variables from the F<config.sh> file (written by Configure) are
  29  stored in the readonly-variable C<%Config>, indexed by their names.
  30  
  31  Values stored in config.sh as 'undef' are returned as undefined
  32  values.  The perl C<exists> function can be used to check if a
  33  named variable exists.
  34  
  35  =over 4
  36  
  37  =item myconfig()
  38  
  39  Returns a textual summary of the major perl configuration values.
  40  See also C<-V> in L<perlrun/Switches>.
  41  
  42  =item config_sh()
  43  
  44  Returns the entire perl configuration information in the form of the
  45  original config.sh shell variable assignment script.
  46  
  47  =item config_re($regex)
  48  
  49  Like config_sh() but returns, as a list, only the config entries who's
  50  names match the $regex.
  51  
  52  =item config_vars(@names)
  53  
  54  Prints to STDOUT the values of the named configuration variable. Each is
  55  printed on a separate line in the form:
  56  
  57    name='value';
  58  
  59  Names which are unknown are output as C<name='UNKNOWN';>.
  60  See also C<-V:name> in L<perlrun/Switches>.
  61  
  62  =back
  63  
  64  =head1 EXAMPLE
  65  
  66  Here's a more sophisticated example of using %Config:
  67  
  68      use Config;
  69      use strict;
  70  
  71      my %sig_num;
  72      my @sig_name;
  73      unless($Config{sig_name} && $Config{sig_num}) {
  74      die "No sigs?";
  75      } else {
  76      my @names = split ' ', $Config{sig_name};
  77      @sig_num{@names} = split ' ', $Config{sig_num};
  78      foreach (@names) {
  79          $sig_name[$sig_num{$_}] ||= $_;
  80      }   
  81      }
  82  
  83      print "signal #17 = $sig_name[17]\n";
  84      if ($sig_num{ALRM}) { 
  85      print "SIGALRM is $sig_num{ALRM}\n";
  86      }   
  87  
  88  =head1 WARNING
  89  
  90  Because this information is not stored within the perl executable
  91  itself it is possible (but unlikely) that the information does not
  92  relate to the actual perl binary which is being used to access it.
  93  
  94  The Config module is installed into the architecture and version
  95  specific library directory ($Config{installarchlib}) and it checks the
  96  perl version number when loaded.
  97  
  98  The values stored in config.sh may be either single-quoted or
  99  double-quoted. Double-quoted strings are handy for those cases where you
 100  need to include escape sequences in the strings. To avoid runtime variable
 101  interpolation, any C<$> and C<@> characters are replaced by C<\$> and
 102  C<\@>, respectively. This isn't foolproof, of course, so don't embed C<\$>
 103  or C<\@> in double-quoted strings unless you're willing to deal with the
 104  consequences. (The slashes will end up escaped and the C<$> or C<@> will
 105  trigger variable interpolation)
 106  
 107  =head1 GLOSSARY
 108  
 109  Most C<Config> variables are determined by the C<Configure> script
 110  on platforms supported by it (which is most UNIX platforms).  Some
 111  platforms have custom-made C<Config> variables, and may thus not have
 112  some of the variables described below, or may have extraneous variables
 113  specific to that particular port.  See the port specific documentation
 114  in such cases.
 115  
 116  =head2 _
 117  
 118  =over 4
 119  
 120  =item C<_a>
 121  
 122  From F<Unix.U>:
 123  
 124  This variable defines the extension used for ordinary library files.
 125  For unix, it is F<.a>.  The F<.> is included.  Other possible
 126  values include F<.lib>.
 127  
 128  =item C<_exe>
 129  
 130  From F<Unix.U>:
 131  
 132  This variable defines the extension used for executable files.
 133  C<DJGPP>, Cygwin and F<OS/2> use F<.exe>.  Stratus C<VOS> uses F<.pm>.
 134  On operating systems which do not require a specific extension
 135  for executable files, this variable is empty.
 136  
 137  =item C<_o>
 138  
 139  From F<Unix.U>:
 140  
 141  This variable defines the extension used for object files.
 142  For unix, it is F<.o>.  The F<.> is included.  Other possible
 143  values include F<.obj>.
 144  
 145  =back
 146  
 147  =head2 a
 148  
 149  =over 4
 150  
 151  =item C<afs>
 152  
 153  From F<afs.U>:
 154  
 155  This variable is set to C<true> if C<AFS> (Andrew File System) is used
 156  on the system, C<false> otherwise.  It is possible to override this
 157  with a hint value or command line option, but you'd better know
 158  what you are doing.
 159  
 160  =item C<afsroot>
 161  
 162  From F<afs.U>:
 163  
 164  This variable is by default set to F</afs>. In the unlikely case
 165  this is not the correct root, it is possible to override this with
 166  a hint value or command line option.  This will be used in subsequent
 167  tests for AFSness in the Perl configure and test process.
 168  
 169  =item C<alignbytes>
 170  
 171  From F<alignbytes.U>:
 172  
 173  This variable holds the number of bytes required to align a
 174  double-- or a long double when applicable. Usual values are
 175  2, 4 and 8.  The default is eight, for safety.
 176  
 177  =item C<ansi2knr>
 178  
 179  From F<ansi2knr.U>:
 180  
 181  This variable is set if the user needs to run ansi2knr.
 182  Currently, this is not supported, so we just abort.
 183  
 184  =item C<aphostname>
 185  
 186  From F<d_gethname.U>:
 187  
 188  This variable contains the command which can be used to compute the
 189  host name. The command is fully qualified by its absolute path, to make
 190  it safe when used by a process with super-user privileges.
 191  
 192  =item C<api_revision>
 193  
 194  From F<patchlevel.U>:
 195  
 196  The three variables, api_revision, api_version, and
 197  api_subversion, specify the version of the oldest perl binary
 198  compatible with the present perl.  In a full version string
 199  such as F<5.6.1>, api_revision is the C<5>.
 200  Prior to 5.5.640, the format was a floating point number,
 201  like 5.00563.
 202  
 203  F<perl.c>:incpush() and F<lib/lib.pm> will automatically search in
 204  F<$sitelib/.>. for older directories back to the limit specified
 205  by these api_ variables.  This is only useful if you have a
 206  perl library directory tree structured like the default one.
 207  See C<INSTALL> for how this works.  The versioned site_perl
 208  directory was introduced in 5.005, so that is the lowest
 209  possible value.  The version list appropriate for the current
 210  system is determined in F<inc_version_list.U>.
 211  
 212  C<XXX> To do:  Since compatibility can depend on compile time
 213  options (such as bincompat, longlong, etc.) it should
 214  (perhaps) be set by Configure, but currently it isn't.
 215  Currently, we read a hard-wired value from F<patchlevel.h>.
 216  Perhaps what we ought to do is take the hard-wired value from
 217  F<patchlevel.h> but then modify it if the current Configure
 218  options warrant.  F<patchlevel.h> then would use an #ifdef guard.
 219  
 220  =item C<api_subversion>
 221  
 222  From F<patchlevel.U>:
 223  
 224  The three variables, api_revision, api_version, and
 225  api_subversion, specify the version of the oldest perl binary
 226  compatible with the present perl.  In a full version string
 227  such as F<5.6.1>, api_subversion is the C<1>.  See api_revision for
 228  full details.
 229  
 230  =item C<api_version>
 231  
 232  From F<patchlevel.U>:
 233  
 234  The three variables, api_revision, api_version, and
 235  api_subversion, specify the version of the oldest perl binary
 236  compatible with the present perl.  In a full version string
 237  such as F<5.6.1>, api_version is the C<6>.  See api_revision for
 238  full details.  As a special case, 5.5.0 is rendered in the
 239  old-style as 5.005.  (In the 5.005_0x maintenance series,
 240  this was the only versioned directory in $sitelib.)
 241  
 242  =item C<api_versionstring>
 243  
 244  From F<patchlevel.U>:
 245  
 246  This variable combines api_revision, api_version, and
 247  api_subversion in a format such as 5.6.1 (or 5_6_1) suitable
 248  for use as a directory name.  This is filesystem dependent.
 249  
 250  =item C<ar>
 251  
 252  From F<Loc.U>:
 253  
 254  This variable is used internally by Configure to determine the
 255  full pathname (if any) of the ar program.  After Configure runs,
 256  the value is reset to a plain C<ar> and is not useful.
 257  
 258  =item C<archlib>
 259  
 260  From F<archlib.U>:
 261  
 262  This variable holds the name of the directory in which the user wants
 263  to put architecture-dependent public library files for $package.
 264  It is most often a local directory such as F</usr/local/lib>.
 265  Programs using this variable must be prepared to deal
 266  with filename expansion.
 267  
 268  =item C<archlibexp>
 269  
 270  From F<archlib.U>:
 271  
 272  This variable is the same as the archlib variable, but is
 273  filename expanded at configuration time, for convenient use.
 274  
 275  =item C<archname>
 276  
 277  From F<archname.U>:
 278  
 279  This variable is a short name to characterize the current
 280  architecture.  It is used mainly to construct the default archlib.
 281  
 282  =item C<archname64>
 283  
 284  From F<use64bits.U>:
 285  
 286  This variable is used for the 64-bitness part of $archname.
 287  
 288  =item C<archobjs>
 289  
 290  From F<Unix.U>:
 291  
 292  This variable defines any additional objects that must be linked
 293  in with the program on this architecture.  On unix, it is usually
 294  empty.  It is typically used to include emulations of unix calls
 295  or other facilities.  For perl on F<OS/2>, for example, this would
 296  include F<os2/os2.obj>.
 297  
 298  =item C<asctime_r_proto>
 299  
 300  From F<d_asctime_r.U>:
 301  
 302  This variable encodes the prototype of asctime_r.
 303  It is zero if d_asctime_r is undef, and one of the
 304  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_asctime_r
 305  is defined.
 306  
 307  =item C<awk>
 308  
 309  From F<Loc.U>:
 310  
 311  This variable is used internally by Configure to determine the
 312  full pathname (if any) of the awk program.  After Configure runs,
 313  the value is reset to a plain C<awk> and is not useful.
 314  
 315  =back
 316  
 317  =head2 b
 318  
 319  =over 4
 320  
 321  =item C<baserev>
 322  
 323  From F<baserev.U>:
 324  
 325  The base revision level of this package, from the F<.package> file.
 326  
 327  =item C<bash>
 328  
 329  From F<Loc.U>:
 330  
 331  This variable is defined but not used by Configure.
 332  The value is a plain '' and is not useful.
 333  
 334  =item C<bin>
 335  
 336  From F<bin.U>:
 337  
 338  This variable holds the name of the directory in which the user wants
 339  to put publicly executable images for the package in question.  It
 340  is most often a local directory such as F</usr/local/bin>. Programs using
 341  this variable must be prepared to deal with F<~name> substitution.
 342  
 343  =item C<binexp>
 344  
 345  From F<bin.U>:
 346  
 347  This is the same as the bin variable, but is filename expanded at
 348  configuration time, for use in your makefiles.
 349  
 350  =item C<bison>
 351  
 352  From F<Loc.U>:
 353  
 354  This variable is used internally by Configure to determine the
 355  full pathname (if any) of the bison program.  After Configure runs,
 356  the value is reset to a plain C<bison> and is not useful.
 357  
 358  =item C<byacc>
 359  
 360  From F<Loc.U>:
 361  
 362  This variable is used internally by Configure to determine the
 363  full pathname (if any) of the byacc program.  After Configure runs,
 364  the value is reset to a plain C<byacc> and is not useful.
 365  
 366  =item C<byteorder>
 367  
 368  From F<byteorder.U>:
 369  
 370  This variable holds the byte order in a C<UV>. In the following,
 371  larger digits indicate more significance.  The variable byteorder
 372  is either 4321 on a big-endian machine, or 1234 on a little-endian,
 373  or 87654321 on a Cray ... or 3412 with weird order !
 374  
 375  =back
 376  
 377  =head2 c
 378  
 379  =over 4
 380  
 381  =item C<c>
 382  
 383  From F<n.U>:
 384  
 385  This variable contains the \c string if that is what causes the echo
 386  command to suppress newline.  Otherwise it is null.  Correct usage is
 387  $echo $n "prompt for a question: $c".
 388  
 389  =item C<castflags>
 390  
 391  From F<d_castneg.U>:
 392  
 393  This variable contains a flag that precise difficulties the
 394  compiler has casting odd floating values to unsigned long:
 395  0 = ok
 396  1 = couldn't cast < 0
 397  2 = couldn't cast >= 0x80000000
 398  4 = couldn't cast in argument expression list
 399  
 400  =item C<cat>
 401  
 402  From F<Loc.U>:
 403  
 404  This variable is used internally by Configure to determine the
 405  full pathname (if any) of the cat program.  After Configure runs,
 406  the value is reset to a plain C<cat> and is not useful.
 407  
 408  =item C<cc>
 409  
 410  From F<cc.U>:
 411  
 412  This variable holds the name of a command to execute a C compiler which
 413  can resolve multiple global references that happen to have the same
 414  name.  Usual values are C<cc> and C<gcc>.
 415  Fervent C<ANSI> compilers may be called C<c89>.  C<AIX> has xlc.
 416  
 417  =item C<cccdlflags>
 418  
 419  From F<dlsrc.U>:
 420  
 421  This variable contains any special flags that might need to be
 422  passed with C<cc -c> to compile modules to be used to create a shared
 423  library that will be used for dynamic loading.  For hpux, this
 424  should be +z.  It is up to the makefile to use it.
 425  
 426  =item C<ccdlflags>
 427  
 428  From F<dlsrc.U>:
 429  
 430  This variable contains any special flags that might need to be
 431  passed to cc to link with a shared library for dynamic loading.
 432  It is up to the makefile to use it.  For sunos 4.1, it should
 433  be empty.
 434  
 435  =item C<ccflags>
 436  
 437  From F<ccflags.U>:
 438  
 439  This variable contains any additional C compiler flags desired by
 440  the user.  It is up to the Makefile to use this.
 441  
 442  =item C<ccflags_uselargefiles>
 443  
 444  From F<uselfs.U>:
 445  
 446  This variable contains the compiler flags needed by large file builds
 447  and added to ccflags by hints files.
 448  
 449  =item C<ccname>
 450  
 451  From F<Checkcc.U>:
 452  
 453  This can set either by hints files or by Configure.  If using
 454  gcc, this is gcc, and if not, usually equal to cc, unimpressive, no?
 455  Some platforms, however, make good use of this by storing the
 456  flavor of the C compiler being used here.  For example if using
 457  the Sun WorkShop suite, ccname will be C<workshop>.
 458  
 459  =item C<ccsymbols>
 460  
 461  From F<Cppsym.U>:
 462  
 463  The variable contains the symbols defined by the C compiler alone.
 464  The symbols defined by cpp or by cc when it calls cpp are not in
 465  this list, see cppsymbols and cppccsymbols.
 466  The list is a space-separated list of symbol=value tokens.
 467  
 468  =item C<ccversion>
 469  
 470  From F<Checkcc.U>:
 471  
 472  This can set either by hints files or by Configure.  If using
 473  a (non-gcc) vendor cc, this variable may contain a version for
 474  the compiler.
 475  
 476  =item C<cf_by>
 477  
 478  From F<cf_who.U>:
 479  
 480  Login name of the person who ran the Configure script and answered the
 481  questions. This is used to tag both F<config.sh> and F<config_h.SH>.
 482  
 483  =item C<cf_email>
 484  
 485  From F<cf_email.U>:
 486  
 487  Electronic mail address of the person who ran Configure. This can be
 488  used by units that require the user's e-mail, like F<MailList.U>.
 489  
 490  =item C<cf_time>
 491  
 492  From F<cf_who.U>:
 493  
 494  Holds the output of the C<date> command when the configuration file was
 495  produced. This is used to tag both F<config.sh> and F<config_h.SH>.
 496  
 497  =item C<chgrp>
 498  
 499  From F<Loc.U>:
 500  
 501  This variable is defined but not used by Configure.
 502  The value is a plain '' and is not useful.
 503  
 504  =item C<chmod>
 505  
 506  From F<Loc.U>:
 507  
 508  This variable is used internally by Configure to determine the
 509  full pathname (if any) of the chmod program.  After Configure runs,
 510  the value is reset to a plain C<chmod> and is not useful.
 511  
 512  =item C<chown>
 513  
 514  From F<Loc.U>:
 515  
 516  This variable is defined but not used by Configure.
 517  The value is a plain '' and is not useful.
 518  
 519  =item C<clocktype>
 520  
 521  From F<d_times.U>:
 522  
 523  This variable holds the type returned by times(). It can be long,
 524  or clock_t on C<BSD> sites (in which case <sys/types.h> should be
 525  included).
 526  
 527  =item C<comm>
 528  
 529  From F<Loc.U>:
 530  
 531  This variable is used internally by Configure to determine the
 532  full pathname (if any) of the comm program.  After Configure runs,
 533  the value is reset to a plain C<comm> and is not useful.
 534  
 535  =item C<compress>
 536  
 537  From F<Loc.U>:
 538  
 539  This variable is defined but not used by Configure.
 540  The value is a plain '' and is not useful.
 541  
 542  =item C<contains>
 543  
 544  From F<contains.U>:
 545  
 546  This variable holds the command to do a grep with a proper return
 547  status.  On most sane systems it is simply C<grep>.  On insane systems
 548  it is a grep followed by a cat followed by a test.  This variable
 549  is primarily for the use of other Configure units.
 550  
 551  =item C<cp>
 552  
 553  From F<Loc.U>:
 554  
 555  This variable is used internally by Configure to determine the
 556  full pathname (if any) of the cp program.  After Configure runs,
 557  the value is reset to a plain C<cp> and is not useful.
 558  
 559  =item C<cpio>
 560  
 561  From F<Loc.U>:
 562  
 563  This variable is defined but not used by Configure.
 564  The value is a plain '' and is not useful.
 565  
 566  =item C<cpp>
 567  
 568  From F<Loc.U>:
 569  
 570  This variable is used internally by Configure to determine the
 571  full pathname (if any) of the cpp program.  After Configure runs,
 572  the value is reset to a plain C<cpp> and is not useful.
 573  
 574  =item C<cpp_stuff>
 575  
 576  From F<cpp_stuff.U>:
 577  
 578  This variable contains an identification of the concatenation mechanism
 579  used by the C preprocessor.
 580  
 581  =item C<cppccsymbols>
 582  
 583  From F<Cppsym.U>:
 584  
 585  The variable contains the symbols defined by the C compiler
 586  when it calls cpp.  The symbols defined by the cc alone or cpp
 587  alone are not in this list, see ccsymbols and cppsymbols.
 588  The list is a space-separated list of symbol=value tokens.
 589  
 590  =item C<cppflags>
 591  
 592  From F<ccflags.U>:
 593  
 594  This variable holds the flags that will be passed to the C pre-
 595  processor. It is up to the Makefile to use it.
 596  
 597  =item C<cpplast>
 598  
 599  From F<cppstdin.U>:
 600  
 601  This variable has the same functionality as cppminus, only it applies
 602  to cpprun and not cppstdin.
 603  
 604  =item C<cppminus>
 605  
 606  From F<cppstdin.U>:
 607  
 608  This variable contains the second part of the string which will invoke
 609  the C preprocessor on the standard input and produce to standard
 610  output.  This variable will have the value C<-> if cppstdin needs
 611  a minus to specify standard input, otherwise the value is "".
 612  
 613  =item C<cpprun>
 614  
 615  From F<cppstdin.U>:
 616  
 617  This variable contains the command which will invoke a C preprocessor
 618  on standard input and put the output to stdout. It is guaranteed not
 619  to be a wrapper and may be a null string if no preprocessor can be
 620  made directly available. This preprocessor might be different from the
 621  one used by the C compiler. Don't forget to append cpplast after the
 622  preprocessor options.
 623  
 624  =item C<cppstdin>
 625  
 626  From F<cppstdin.U>:
 627  
 628  This variable contains the command which will invoke the C
 629  preprocessor on standard input and put the output to stdout.
 630  It is primarily used by other Configure units that ask about
 631  preprocessor symbols.
 632  
 633  =item C<cppsymbols>
 634  
 635  From F<Cppsym.U>:
 636  
 637  The variable contains the symbols defined by the C preprocessor
 638  alone.  The symbols defined by cc or by cc when it calls cpp are
 639  not in this list, see ccsymbols and cppccsymbols.
 640  The list is a space-separated list of symbol=value tokens.
 641  
 642  =item C<crypt_r_proto>
 643  
 644  From F<d_crypt_r.U>:
 645  
 646  This variable encodes the prototype of crypt_r.
 647  It is zero if d_crypt_r is undef, and one of the
 648  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_crypt_r
 649  is defined.
 650  
 651  =item C<cryptlib>
 652  
 653  From F<d_crypt.U>:
 654  
 655  This variable holds -lcrypt or the path to a F<libcrypt.a> archive if
 656  the crypt() function is not defined in the standard C library. It is
 657  up to the Makefile to use this.
 658  
 659  =item C<csh>
 660  
 661  From F<Loc.U>:
 662  
 663  This variable is used internally by Configure to determine the
 664  full pathname (if any) of the csh program.  After Configure runs,
 665  the value is reset to a plain C<csh> and is not useful.
 666  
 667  =item C<ctermid_r_proto>
 668  
 669  From F<d_ctermid_r.U>:
 670  
 671  This variable encodes the prototype of ctermid_r.
 672  It is zero if d_ctermid_r is undef, and one of the
 673  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_ctermid_r
 674  is defined.
 675  
 676  =item C<ctime_r_proto>
 677  
 678  From F<d_ctime_r.U>:
 679  
 680  This variable encodes the prototype of ctime_r.
 681  It is zero if d_ctime_r is undef, and one of the
 682  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_ctime_r
 683  is defined.
 684  
 685  =back
 686  
 687  =head2 d
 688  
 689  =over 4
 690  
 691  =item C<d__fwalk>
 692  
 693  From F<d__fwalk.U>:
 694  
 695  This variable conditionally defines C<HAS__FWALK> if _fwalk() is
 696  available to apply a function to all the file handles.
 697  
 698  =item C<d_access>
 699  
 700  From F<d_access.U>:
 701  
 702  This variable conditionally defines C<HAS_ACCESS> if the access() system
 703  call is available to check for access permissions using real IDs.
 704  
 705  =item C<d_accessx>
 706  
 707  From F<d_accessx.U>:
 708  
 709  This variable conditionally defines the C<HAS_ACCESSX> symbol, which
 710  indicates to the C program that the accessx() routine is available.
 711  
 712  =item C<d_aintl>
 713  
 714  From F<d_aintl.U>:
 715  
 716  This variable conditionally defines the C<HAS_AINTL> symbol, which
 717  indicates to the C program that the aintl() routine is available.
 718  If copysignl is also present we can emulate modfl.
 719  
 720  =item C<d_alarm>
 721  
 722  From F<d_alarm.U>:
 723  
 724  This variable conditionally defines the C<HAS_ALARM> symbol, which
 725  indicates to the C program that the alarm() routine is available.
 726  
 727  =item C<d_archlib>
 728  
 729  From F<archlib.U>:
 730  
 731  This variable conditionally defines C<ARCHLIB> to hold the pathname
 732  of architecture-dependent library files for $package.  If
 733  $archlib is the same as $privlib, then this is set to undef.
 734  
 735  =item C<d_asctime_r>
 736  
 737  From F<d_asctime_r.U>:
 738  
 739  This variable conditionally defines the C<HAS_ASCTIME_R> symbol,
 740  which indicates to the C program that the asctime_r()
 741  routine is available.
 742  
 743  =item C<d_atolf>
 744  
 745  From F<atolf.U>:
 746  
 747  This variable conditionally defines the C<HAS_ATOLF> symbol, which
 748  indicates to the C program that the atolf() routine is available.
 749  
 750  =item C<d_atoll>
 751  
 752  From F<atoll.U>:
 753  
 754  This variable conditionally defines the C<HAS_ATOLL> symbol, which
 755  indicates to the C program that the atoll() routine is available.
 756  
 757  =item C<d_attribute_format>
 758  
 759  From F<d_attribut.U>:
 760  
 761  This variable conditionally defines C<HASATTRIBUTE_FORMAT>, which
 762  indicates the C compiler can check for printf-like formats.
 763  
 764  =item C<d_attribute_malloc>
 765  
 766  From F<d_attribut.U>:
 767  
 768  This variable conditionally defines C<HASATTRIBUTE_MALLOC>, which
 769  indicates the C compiler can understand functions as having
 770  malloc-like semantics.
 771  
 772  =item C<d_attribute_nonnull>
 773  
 774  From F<d_attribut.U>:
 775  
 776  This variable conditionally defines C<HASATTRIBUTE_NONNULL>, which
 777  indicates that the C compiler can know that certain arguments
 778  must not be C<NULL>, and will check accordingly at compile time.
 779  
 780  =item C<d_attribute_noreturn>
 781  
 782  From F<d_attribut.U>:
 783  
 784  This variable conditionally defines C<HASATTRIBUTE_NORETURN>, which
 785  indicates that the C compiler can know that certain functions
 786  are guaranteed never to return.
 787  
 788  =item C<d_attribute_pure>
 789  
 790  From F<d_attribut.U>:
 791  
 792  This variable conditionally defines C<HASATTRIBUTE_PURE>, which
 793  indicates that the C compiler can know that certain functions
 794  are C<pure> functions, meaning that they have no side effects, and
 795  only rely on function input F<and/or> global data for their results.
 796  
 797  =item C<d_attribute_unused>
 798  
 799  From F<d_attribut.U>:
 800  
 801  This variable conditionally defines C<HASATTRIBUTE_UNUSED>, which
 802  indicates that the C compiler can know that certain variables
 803  and arguments may not always be used, and to not throw warnings
 804  if they don't get used.
 805  
 806  =item C<d_attribute_warn_unused_result>
 807  
 808  From F<d_attribut.U>:
 809  
 810  This variable conditionally defines
 811  C<HASATTRIBUTE_WARN_UNUSED_RESULT>, which indicates that the C
 812  compiler can know that certain functions have a return values
 813  that must not be ignored, such as malloc() or open().
 814  
 815  =item C<d_bcmp>
 816  
 817  From F<d_bcmp.U>:
 818  
 819  This variable conditionally defines the C<HAS_BCMP> symbol if
 820  the bcmp() routine is available to compare strings.
 821  
 822  =item C<d_bcopy>
 823  
 824  From F<d_bcopy.U>:
 825  
 826  This variable conditionally defines the C<HAS_BCOPY> symbol if
 827  the bcopy() routine is available to copy strings.
 828  
 829  =item C<d_bsd>
 830  
 831  From F<Guess.U>:
 832  
 833  This symbol conditionally defines the symbol C<BSD> when running on a
 834  C<BSD> system.
 835  
 836  =item C<d_bsdgetpgrp>
 837  
 838  From F<d_getpgrp.U>:
 839  
 840  This variable conditionally defines C<USE_BSD_GETPGRP> if
 841  getpgrp needs one arguments whereas C<USG> one needs none.
 842  
 843  =item C<d_bsdsetpgrp>
 844  
 845  From F<d_setpgrp.U>:
 846  
 847  This variable conditionally defines C<USE_BSD_SETPGRP> if
 848  setpgrp needs two arguments whereas C<USG> one needs none.
 849  See also d_setpgid for a C<POSIX> interface.
 850  
 851  =item C<d_builtin_choose_expr>
 852  
 853  From F<d_builtin.U>:
 854  
 855  This conditionally defines C<HAS_BUILTIN_CHOOSE_EXPR>, which
 856  indicates that the compiler supports __builtin_choose_expr(x,y,z).
 857  This built-in function is analogous to the C<x?y:z> operator in C,
 858  except that the expression returned has its type unaltered by
 859  promotion rules. Also, the built-in function does not evaluate
 860  the expression that was not chosen.
 861  
 862  =item C<d_builtin_expect>
 863  
 864  From F<d_builtin.U>:
 865  
 866  This conditionally defines C<HAS_BUILTIN_EXPECT>, which indicates
 867  that the compiler supports __builtin_expect(exp,c).  You may use
 868  __builtin_expect to provide the compiler with branch prediction
 869  information.
 870  
 871  =item C<d_bzero>
 872  
 873  From F<d_bzero.U>:
 874  
 875  This variable conditionally defines the C<HAS_BZERO> symbol if
 876  the bzero() routine is available to set memory to 0.
 877  
 878  =item C<d_c99_variadic_macros>
 879  
 880  From F<d_c99_variadic.U>:
 881  
 882  This variable conditionally defines the HAS_C99_VARIADIC_MACROS
 883  symbol, which indicates to the C program that C99 variadic macros
 884  are available.
 885  
 886  =item C<d_casti32>
 887  
 888  From F<d_casti32.U>:
 889  
 890  This variable conditionally defines CASTI32, which indicates
 891  whether the C compiler can cast large floats to 32-bit ints.
 892  
 893  =item C<d_castneg>
 894  
 895  From F<d_castneg.U>:
 896  
 897  This variable conditionally defines C<CASTNEG>, which indicates
 898  wether the C compiler can cast negative float to unsigned.
 899  
 900  =item C<d_charvspr>
 901  
 902  From F<d_vprintf.U>:
 903  
 904  This variable conditionally defines C<CHARVSPRINTF> if this system
 905  has vsprintf returning type (char*).  The trend seems to be to
 906  declare it as "int vsprintf()".
 907  
 908  =item C<d_chown>
 909  
 910  From F<d_chown.U>:
 911  
 912  This variable conditionally defines the C<HAS_CHOWN> symbol, which
 913  indicates to the C program that the chown() routine is available.
 914  
 915  =item C<d_chroot>
 916  
 917  From F<d_chroot.U>:
 918  
 919  This variable conditionally defines the C<HAS_CHROOT> symbol, which
 920  indicates to the C program that the chroot() routine is available.
 921  
 922  =item C<d_chsize>
 923  
 924  From F<d_chsize.U>:
 925  
 926  This variable conditionally defines the C<CHSIZE> symbol, which
 927  indicates to the C program that the chsize() routine is available
 928  to truncate files.  You might need a -lx to get this routine.
 929  
 930  =item C<d_class>
 931  
 932  From F<d_class.U>:
 933  
 934  This variable conditionally defines the C<HAS_CLASS> symbol, which
 935  indicates to the C program that the class() routine is available.
 936  
 937  =item C<d_clearenv>
 938  
 939  From F<d_clearenv.U>:
 940  
 941  This variable conditionally defines the C<HAS_CLEARENV> symbol, which
 942  indicates to the C program that the clearenv () routine is available.
 943  
 944  =item C<d_closedir>
 945  
 946  From F<d_closedir.U>:
 947  
 948  This variable conditionally defines C<HAS_CLOSEDIR> if closedir() is
 949  available.
 950  
 951  =item C<d_cmsghdr_s>
 952  
 953  From F<d_cmsghdr_s.U>:
 954  
 955  This variable conditionally defines the C<HAS_STRUCT_CMSGHDR> symbol,
 956  which indicates that the struct cmsghdr is supported.
 957  
 958  =item C<d_const>
 959  
 960  From F<d_const.U>:
 961  
 962  This variable conditionally defines the C<HASCONST> symbol, which
 963  indicates to the C program that this C compiler knows about the
 964  const type.
 965  
 966  =item C<d_copysignl>
 967  
 968  From F<d_copysignl.U>:
 969  
 970  This variable conditionally defines the C<HAS_COPYSIGNL> symbol, which
 971  indicates to the C program that the copysignl() routine is available.
 972  If aintl is also present we can emulate modfl.
 973  
 974  =item C<d_cplusplus>
 975  
 976  From F<d_cplusplus.U>:
 977  
 978  This variable conditionally defines the C<USE_CPLUSPLUS> symbol, which
 979  indicates that a C++ compiler was used to compiled Perl and will be
 980  used to compile extensions.
 981  
 982  =item C<d_crypt>
 983  
 984  From F<d_crypt.U>:
 985  
 986  This variable conditionally defines the C<CRYPT> symbol, which
 987  indicates to the C program that the crypt() routine is available
 988  to encrypt passwords and the like.
 989  
 990  =item C<d_crypt_r>
 991  
 992  From F<d_crypt_r.U>:
 993  
 994  This variable conditionally defines the C<HAS_CRYPT_R> symbol,
 995  which indicates to the C program that the crypt_r()
 996  routine is available.
 997  
 998  =item C<d_csh>
 999  
1000  From F<d_csh.U>:
1001  
1002  This variable conditionally defines the C<CSH> symbol, which
1003  indicates to the C program that the C-shell exists.
1004  
1005  =item C<d_ctermid>
1006  
1007  From F<d_ctermid.U>:
1008  
1009  This variable conditionally defines C<CTERMID> if ctermid() is
1010  available to generate filename for terminal.
1011  
1012  =item C<d_ctermid_r>
1013  
1014  From F<d_ctermid_r.U>:
1015  
1016  This variable conditionally defines the C<HAS_CTERMID_R> symbol,
1017  which indicates to the C program that the ctermid_r()
1018  routine is available.
1019  
1020  =item C<d_ctime_r>
1021  
1022  From F<d_ctime_r.U>:
1023  
1024  This variable conditionally defines the C<HAS_CTIME_R> symbol,
1025  which indicates to the C program that the ctime_r()
1026  routine is available.
1027  
1028  =item C<d_cuserid>
1029  
1030  From F<d_cuserid.U>:
1031  
1032  This variable conditionally defines the C<HAS_CUSERID> symbol, which
1033  indicates to the C program that the cuserid() routine is available
1034  to get character login names.
1035  
1036  =item C<d_dbl_dig>
1037  
1038  From F<d_dbl_dig.U>:
1039  
1040  This variable conditionally defines d_dbl_dig if this system's
1041  header files provide C<DBL_DIG>, which is the number of significant
1042  digits in a double precision number.
1043  
1044  =item C<d_dbminitproto>
1045  
1046  From F<d_dbminitproto.U>:
1047  
1048  This variable conditionally defines the C<HAS_DBMINIT_PROTO> symbol,
1049  which indicates to the C program that the system provides
1050  a prototype for the dbminit() function.  Otherwise, it is
1051  up to the program to supply one.
1052  
1053  =item C<d_difftime>
1054  
1055  From F<d_difftime.U>:
1056  
1057  This variable conditionally defines the C<HAS_DIFFTIME> symbol, which
1058  indicates to the C program that the difftime() routine is available.
1059  
1060  =item C<d_dir_dd_fd>
1061  
1062  From F<d_dir_dd_fd.U>:
1063  
1064  This variable conditionally defines the C<HAS_DIR_DD_FD> symbol, which
1065  indicates that the C<DIR> directory stream type contains a member
1066  variable called dd_fd.
1067  
1068  =item C<d_dirfd>
1069  
1070  From F<d_dirfd.U>:
1071  
1072  This variable conditionally defines the C<HAS_DIRFD> constant,
1073  which indicates to the C program that dirfd() is available
1074  to return the file descriptor of a directory stream.
1075  
1076  =item C<d_dirnamlen>
1077  
1078  From F<i_dirent.U>:
1079  
1080  This variable conditionally defines C<DIRNAMLEN>, which indicates
1081  to the C program that the length of directory entry names is
1082  provided by a d_namelen field.
1083  
1084  =item C<d_dlerror>
1085  
1086  From F<d_dlerror.U>:
1087  
1088  This variable conditionally defines the C<HAS_DLERROR> symbol, which
1089  indicates to the C program that the dlerror() routine is available.
1090  
1091  =item C<d_dlopen>
1092  
1093  From F<d_dlopen.U>:
1094  
1095  This variable conditionally defines the C<HAS_DLOPEN> symbol, which
1096  indicates to the C program that the dlopen() routine is available.
1097  
1098  =item C<d_dlsymun>
1099  
1100  From F<d_dlsymun.U>:
1101  
1102  This variable conditionally defines C<DLSYM_NEEDS_UNDERSCORE>, which
1103  indicates that we need to prepend an underscore to the symbol
1104  name before calling dlsym().
1105  
1106  =item C<d_dosuid>
1107  
1108  From F<d_dosuid.U>:
1109  
1110  This variable conditionally defines the symbol C<DOSUID>, which
1111  tells the C program that it should insert setuid emulation code
1112  on hosts which have setuid #! scripts disabled.
1113  
1114  =item C<d_drand48_r>
1115  
1116  From F<d_drand48_r.U>:
1117  
1118  This variable conditionally defines the HAS_DRAND48_R symbol,
1119  which indicates to the C program that the drand48_r()
1120  routine is available.
1121  
1122  =item C<d_drand48proto>
1123  
1124  From F<d_drand48proto.U>:
1125  
1126  This variable conditionally defines the HAS_DRAND48_PROTO symbol,
1127  which indicates to the C program that the system provides
1128  a prototype for the drand48() function.  Otherwise, it is
1129  up to the program to supply one.
1130  
1131  =item C<d_dup2>
1132  
1133  From F<d_dup2.U>:
1134  
1135  This variable conditionally defines HAS_DUP2 if dup2() is
1136  available to duplicate file descriptors.
1137  
1138  =item C<d_eaccess>
1139  
1140  From F<d_eaccess.U>:
1141  
1142  This variable conditionally defines the C<HAS_EACCESS> symbol, which
1143  indicates to the C program that the eaccess() routine is available.
1144  
1145  =item C<d_endgrent>
1146  
1147  From F<d_endgrent.U>:
1148  
1149  This variable conditionally defines the C<HAS_ENDGRENT> symbol, which
1150  indicates to the C program that the endgrent() routine is available
1151  for sequential access of the group database.
1152  
1153  =item C<d_endgrent_r>
1154  
1155  From F<d_endgrent_r.U>:
1156  
1157  This variable conditionally defines the C<HAS_ENDGRENT_R> symbol,
1158  which indicates to the C program that the endgrent_r()
1159  routine is available.
1160  
1161  =item C<d_endhent>
1162  
1163  From F<d_endhent.U>:
1164  
1165  This variable conditionally defines C<HAS_ENDHOSTENT> if endhostent() is
1166  available to close whatever was being used for host queries.
1167  
1168  =item C<d_endhostent_r>
1169  
1170  From F<d_endhostent_r.U>:
1171  
1172  This variable conditionally defines the C<HAS_ENDHOSTENT_R> symbol,
1173  which indicates to the C program that the endhostent_r()
1174  routine is available.
1175  
1176  =item C<d_endnent>
1177  
1178  From F<d_endnent.U>:
1179  
1180  This variable conditionally defines C<HAS_ENDNETENT> if endnetent() is
1181  available to close whatever was being used for network queries.
1182  
1183  =item C<d_endnetent_r>
1184  
1185  From F<d_endnetent_r.U>:
1186  
1187  This variable conditionally defines the C<HAS_ENDNETENT_R> symbol,
1188  which indicates to the C program that the endnetent_r()
1189  routine is available.
1190  
1191  =item C<d_endpent>
1192  
1193  From F<d_endpent.U>:
1194  
1195  This variable conditionally defines C<HAS_ENDPROTOENT> if endprotoent() is
1196  available to close whatever was being used for protocol queries.
1197  
1198  =item C<d_endprotoent_r>
1199  
1200  From F<d_endprotoent_r.U>:
1201  
1202  This variable conditionally defines the C<HAS_ENDPROTOENT_R> symbol,
1203  which indicates to the C program that the endprotoent_r()
1204  routine is available.
1205  
1206  =item C<d_endpwent>
1207  
1208  From F<d_endpwent.U>:
1209  
1210  This variable conditionally defines the C<HAS_ENDPWENT> symbol, which
1211  indicates to the C program that the endpwent() routine is available
1212  for sequential access of the passwd database.
1213  
1214  =item C<d_endpwent_r>
1215  
1216  From F<d_endpwent_r.U>:
1217  
1218  This variable conditionally defines the C<HAS_ENDPWENT_R> symbol,
1219  which indicates to the C program that the endpwent_r()
1220  routine is available.
1221  
1222  =item C<d_endsent>
1223  
1224  From F<d_endsent.U>:
1225  
1226  This variable conditionally defines C<HAS_ENDSERVENT> if endservent() is
1227  available to close whatever was being used for service queries.
1228  
1229  =item C<d_endservent_r>
1230  
1231  From F<d_endservent_r.U>:
1232  
1233  This variable conditionally defines the C<HAS_ENDSERVENT_R> symbol,
1234  which indicates to the C program that the endservent_r()
1235  routine is available.
1236  
1237  =item C<d_eofnblk>
1238  
1239  From F<nblock_io.U>:
1240  
1241  This variable conditionally defines C<EOF_NONBLOCK> if C<EOF> can be seen
1242  when reading from a non-blocking I/O source.
1243  
1244  =item C<d_eunice>
1245  
1246  From F<Guess.U>:
1247  
1248  This variable conditionally defines the symbols C<EUNICE> and C<VAX>, which
1249  alerts the C program that it must deal with ideosyncracies of C<VMS>.
1250  
1251  =item C<d_faststdio>
1252  
1253  From F<d_faststdio.U>:
1254  
1255  This variable conditionally defines the C<HAS_FAST_STDIO> symbol,
1256  which indicates to the C program that the "fast stdio" is available
1257  to manipulate the stdio buffers directly.
1258  
1259  =item C<d_fchdir>
1260  
1261  From F<d_fchdir.U>:
1262  
1263  This variable conditionally defines the C<HAS_FCHDIR> symbol, which
1264  indicates to the C program that the fchdir() routine is available.
1265  
1266  =item C<d_fchmod>
1267  
1268  From F<d_fchmod.U>:
1269  
1270  This variable conditionally defines the C<HAS_FCHMOD> symbol, which
1271  indicates to the C program that the fchmod() routine is available
1272  to change mode of opened files.
1273  
1274  =item C<d_fchown>
1275  
1276  From F<d_fchown.U>:
1277  
1278  This variable conditionally defines the C<HAS_FCHOWN> symbol, which
1279  indicates to the C program that the fchown() routine is available
1280  to change ownership of opened files.
1281  
1282  =item C<d_fcntl>
1283  
1284  From F<d_fcntl.U>:
1285  
1286  This variable conditionally defines the C<HAS_FCNTL> symbol, and indicates
1287  whether the fcntl() function exists
1288  
1289  =item C<d_fcntl_can_lock>
1290  
1291  From F<d_fcntl_can_lock.U>:
1292  
1293  This variable conditionally defines the C<FCNTL_CAN_LOCK> symbol
1294  and indicates whether file locking with fcntl() works.
1295  
1296  =item C<d_fd_macros>
1297  
1298  From F<d_fd_set.U>:
1299  
1300  This variable contains the eventual value of the C<HAS_FD_MACROS> symbol,
1301  which indicates if your C compiler knows about the macros which
1302  manipulate an fd_set.
1303  
1304  =item C<d_fd_set>
1305  
1306  From F<d_fd_set.U>:
1307  
1308  This variable contains the eventual value of the C<HAS_FD_SET> symbol,
1309  which indicates if your C compiler knows about the fd_set typedef.
1310  
1311  =item C<d_fds_bits>
1312  
1313  From F<d_fd_set.U>:
1314  
1315  This variable contains the eventual value of the C<HAS_FDS_BITS> symbol,
1316  which indicates if your fd_set typedef contains the fds_bits member.
1317  If you have an fd_set typedef, but the dweebs who installed it did
1318  a half-fast job and neglected to provide the macros to manipulate
1319  an fd_set, C<HAS_FDS_BITS> will let us know how to fix the gaffe.
1320  
1321  =item C<d_fgetpos>
1322  
1323  From F<d_fgetpos.U>:
1324  
1325  This variable conditionally defines C<HAS_FGETPOS> if fgetpos() is
1326  available to get the file position indicator.
1327  
1328  =item C<d_finite>
1329  
1330  From F<d_finite.U>:
1331  
1332  This variable conditionally defines the C<HAS_FINITE> symbol, which
1333  indicates to the C program that the finite() routine is available.
1334  
1335  =item C<d_finitel>
1336  
1337  From F<d_finitel.U>:
1338  
1339  This variable conditionally defines the C<HAS_FINITEL> symbol, which
1340  indicates to the C program that the finitel() routine is available.
1341  
1342  =item C<d_flexfnam>
1343  
1344  From F<d_flexfnam.U>:
1345  
1346  This variable conditionally defines the C<FLEXFILENAMES> symbol, which
1347  indicates that the system supports filenames longer than 14 characters.
1348  
1349  =item C<d_flock>
1350  
1351  From F<d_flock.U>:
1352  
1353  This variable conditionally defines C<HAS_FLOCK> if flock() is
1354  available to do file locking.
1355  
1356  =item C<d_flockproto>
1357  
1358  From F<d_flockproto.U>:
1359  
1360  This variable conditionally defines the C<HAS_FLOCK_PROTO> symbol,
1361  which indicates to the C program that the system provides
1362  a prototype for the flock() function.  Otherwise, it is
1363  up to the program to supply one.
1364  
1365  =item C<d_fork>
1366  
1367  From F<d_fork.U>:
1368  
1369  This variable conditionally defines the C<HAS_FORK> symbol, which
1370  indicates to the C program that the fork() routine is available.
1371  
1372  =item C<d_fp_class>
1373  
1374  From F<d_fp_class.U>:
1375  
1376  This variable conditionally defines the C<HAS_FP_CLASS> symbol, which
1377  indicates to the C program that the fp_class() routine is available.
1378  
1379  =item C<d_fpathconf>
1380  
1381  From F<d_pathconf.U>:
1382  
1383  This variable conditionally defines the C<HAS_FPATHCONF> symbol, which
1384  indicates to the C program that the pathconf() routine is available
1385  to determine file-system related limits and options associated
1386  with a given open file descriptor.
1387  
1388  =item C<d_fpclass>
1389  
1390  From F<d_fpclass.U>:
1391  
1392  This variable conditionally defines the C<HAS_FPCLASS> symbol, which
1393  indicates to the C program that the fpclass() routine is available.
1394  
1395  =item C<d_fpclassify>
1396  
1397  From F<d_fpclassify.U>:
1398  
1399  This variable conditionally defines the C<HAS_FPCLASSIFY> symbol, which
1400  indicates to the C program that the fpclassify() routine is available.
1401  
1402  =item C<d_fpclassl>
1403  
1404  From F<d_fpclassl.U>:
1405  
1406  This variable conditionally defines the C<HAS_FPCLASSL> symbol, which
1407  indicates to the C program that the fpclassl() routine is available.
1408  
1409  =item C<d_fpos64_t>
1410  
1411  From F<d_fpos64_t.U>:
1412  
1413  This symbol will be defined if the C compiler supports fpos64_t.
1414  
1415  =item C<d_frexpl>
1416  
1417  From F<d_frexpl.U>:
1418  
1419  This variable conditionally defines the C<HAS_FREXPL> symbol, which
1420  indicates to the C program that the frexpl() routine is available.
1421  
1422  =item C<d_fs_data_s>
1423  
1424  From F<d_fs_data_s.U>:
1425  
1426  This variable conditionally defines the C<HAS_STRUCT_FS_DATA> symbol,
1427  which indicates that the struct fs_data is supported.
1428  
1429  =item C<d_fseeko>
1430  
1431  From F<d_fseeko.U>:
1432  
1433  This variable conditionally defines the C<HAS_FSEEKO> symbol, which
1434  indicates to the C program that the fseeko() routine is available.
1435  
1436  =item C<d_fsetpos>
1437  
1438  From F<d_fsetpos.U>:
1439  
1440  This variable conditionally defines C<HAS_FSETPOS> if fsetpos() is
1441  available to set the file position indicator.
1442  
1443  =item C<d_fstatfs>
1444  
1445  From F<d_fstatfs.U>:
1446  
1447  This variable conditionally defines the C<HAS_FSTATFS> symbol, which
1448  indicates to the C program that the fstatfs() routine is available.
1449  
1450  =item C<d_fstatvfs>
1451  
1452  From F<d_statvfs.U>:
1453  
1454  This variable conditionally defines the C<HAS_FSTATVFS> symbol, which
1455  indicates to the C program that the fstatvfs() routine is available.
1456  
1457  =item C<d_fsync>
1458  
1459  From F<d_fsync.U>:
1460  
1461  This variable conditionally defines the C<HAS_FSYNC> symbol, which
1462  indicates to the C program that the fsync() routine is available.
1463  
1464  =item C<d_ftello>
1465  
1466  From F<d_ftello.U>:
1467  
1468  This variable conditionally defines the C<HAS_FTELLO> symbol, which
1469  indicates to the C program that the ftello() routine is available.
1470  
1471  =item C<d_ftime>
1472  
1473  From F<d_ftime.U>:
1474  
1475  This variable conditionally defines the C<HAS_FTIME> symbol, which indicates
1476  that the ftime() routine exists.  The ftime() routine is basically
1477  a sub-second accuracy clock.
1478  
1479  =item C<d_futimes>
1480  
1481  From F<d_futimes.U>:
1482  
1483  This variable conditionally defines the C<HAS_FUTIMES> symbol, which
1484  indicates to the C program that the futimes() routine is available.
1485  
1486  =item C<d_Gconvert>
1487  
1488  From F<d_gconvert.U>:
1489  
1490  This variable holds what Gconvert is defined as to convert
1491  floating point numbers into strings.  By default, Configure
1492  sets C<this> macro to use the first of gconvert, gcvt, or sprintf
1493  that pass sprintf-%g-like behaviour tests.  If perl is using
1494  long doubles, the macro uses the first of the following
1495  functions that pass Configure's tests: qgcvt, sprintf (if
1496  Configure knows how to make sprintf format long doubles--see
1497  sPRIgldbl), gconvert, gcvt, and sprintf (casting to double).
1498  The gconvert_preference and gconvert_ld_preference variables
1499  can be used to alter Configure's preferences, for doubles and
1500  long doubles, respectively.  If present, they contain a
1501  space-separated list of one or more of the above function
1502  names in the order they should be tried.
1503  
1504  d_Gconvert may be set to override Configure with a platform-
1505  specific function.  If this function expects a double, a
1506  different value may need to be set by the F<uselongdouble.cbu>
1507  call-back unit so that long doubles can be formatted without
1508  loss of precision.
1509  
1510  =item C<d_getcwd>
1511  
1512  From F<d_getcwd.U>:
1513  
1514  This variable conditionally defines the C<HAS_GETCWD> symbol, which
1515  indicates to the C program that the getcwd() routine is available
1516  to get the current working directory.
1517  
1518  =item C<d_getespwnam>
1519  
1520  From F<d_getespwnam.U>:
1521  
1522  This variable conditionally defines C<HAS_GETESPWNAM> if getespwnam() is
1523  available to retrieve enchanced (shadow) password entries by name.
1524  
1525  =item C<d_getfsstat>
1526  
1527  From F<d_getfsstat.U>:
1528  
1529  This variable conditionally defines the C<HAS_GETFSSTAT> symbol, which
1530  indicates to the C program that the getfsstat() routine is available.
1531  
1532  =item C<d_getgrent>
1533  
1534  From F<d_getgrent.U>:
1535  
1536  This variable conditionally defines the C<HAS_GETGRENT> symbol, which
1537  indicates to the C program that the getgrent() routine is available
1538  for sequential access of the group database.
1539  
1540  =item C<d_getgrent_r>
1541  
1542  From F<d_getgrent_r.U>:
1543  
1544  This variable conditionally defines the C<HAS_GETGRENT_R> symbol,
1545  which indicates to the C program that the getgrent_r()
1546  routine is available.
1547  
1548  =item C<d_getgrgid_r>
1549  
1550  From F<d_getgrgid_r.U>:
1551  
1552  This variable conditionally defines the C<HAS_GETGRGID_R> symbol,
1553  which indicates to the C program that the getgrgid_r()
1554  routine is available.
1555  
1556  =item C<d_getgrnam_r>
1557  
1558  From F<d_getgrnam_r.U>:
1559  
1560  This variable conditionally defines the C<HAS_GETGRNAM_R> symbol,
1561  which indicates to the C program that the getgrnam_r()
1562  routine is available.
1563  
1564  =item C<d_getgrps>
1565  
1566  From F<d_getgrps.U>:
1567  
1568  This variable conditionally defines the C<HAS_GETGROUPS> symbol, which
1569  indicates to the C program that the getgroups() routine is available
1570  to get the list of process groups.
1571  
1572  =item C<d_gethbyaddr>
1573  
1574  From F<d_gethbyad.U>:
1575  
1576  This variable conditionally defines the C<HAS_GETHOSTBYADDR> symbol, which
1577  indicates to the C program that the gethostbyaddr() routine is available
1578  to look up hosts by their C<IP> addresses.
1579  
1580  =item C<d_gethbyname>
1581  
1582  From F<d_gethbynm.U>:
1583  
1584  This variable conditionally defines the C<HAS_GETHOSTBYNAME> symbol, which
1585  indicates to the C program that the gethostbyname() routine is available
1586  to look up host names in some data base or other.
1587  
1588  =item C<d_gethent>
1589  
1590  From F<d_gethent.U>:
1591  
1592  This variable conditionally defines C<HAS_GETHOSTENT> if gethostent() is
1593  available to look up host names in some data base or another.
1594  
1595  =item C<d_gethname>
1596  
1597  From F<d_gethname.U>:
1598  
1599  This variable conditionally defines the C<HAS_GETHOSTNAME> symbol, which
1600  indicates to the C program that the gethostname() routine may be
1601  used to derive the host name.
1602  
1603  =item C<d_gethostbyaddr_r>
1604  
1605  From F<d_gethostbyaddr_r.U>:
1606  
1607  This variable conditionally defines the C<HAS_GETHOSTBYADDR_R> symbol,
1608  which indicates to the C program that the gethostbyaddr_r()
1609  routine is available.
1610  
1611  =item C<d_gethostbyname_r>
1612  
1613  From F<d_gethostbyname_r.U>:
1614  
1615  This variable conditionally defines the C<HAS_GETHOSTBYNAME_R> symbol,
1616  which indicates to the C program that the gethostbyname_r()
1617  routine is available.
1618  
1619  =item C<d_gethostent_r>
1620  
1621  From F<d_gethostent_r.U>:
1622  
1623  This variable conditionally defines the C<HAS_GETHOSTENT_R> symbol,
1624  which indicates to the C program that the gethostent_r()
1625  routine is available.
1626  
1627  =item C<d_gethostprotos>
1628  
1629  From F<d_gethostprotos.U>:
1630  
1631  This variable conditionally defines the C<HAS_GETHOST_PROTOS> symbol,
1632  which indicates to the C program that <netdb.h> supplies
1633  prototypes for the various gethost*() functions.
1634  See also F<netdbtype.U> for probing for various netdb types.
1635  
1636  =item C<d_getitimer>
1637  
1638  From F<d_getitimer.U>:
1639  
1640  This variable conditionally defines the C<HAS_GETITIMER> symbol, which
1641  indicates to the C program that the getitimer() routine is available.
1642  
1643  =item C<d_getlogin>
1644  
1645  From F<d_getlogin.U>:
1646  
1647  This variable conditionally defines the C<HAS_GETLOGIN> symbol, which
1648  indicates to the C program that the getlogin() routine is available
1649  to get the login name.
1650  
1651  =item C<d_getlogin_r>
1652  
1653  From F<d_getlogin_r.U>:
1654  
1655  This variable conditionally defines the C<HAS_GETLOGIN_R> symbol,
1656  which indicates to the C program that the getlogin_r()
1657  routine is available.
1658  
1659  =item C<d_getmnt>
1660  
1661  From F<d_getmnt.U>:
1662  
1663  This variable conditionally defines the C<HAS_GETMNT> symbol, which
1664  indicates to the C program that the getmnt() routine is available
1665  to retrieve one or more mount info blocks by filename.
1666  
1667  =item C<d_getmntent>
1668  
1669  From F<d_getmntent.U>:
1670  
1671  This variable conditionally defines the C<HAS_GETMNTENT> symbol, which
1672  indicates to the C program that the getmntent() routine is available
1673  to iterate through mounted files to get their mount info.
1674  
1675  =item C<d_getnbyaddr>
1676  
1677  From F<d_getnbyad.U>:
1678  
1679  This variable conditionally defines the C<HAS_GETNETBYADDR> symbol, which
1680  indicates to the C program that the getnetbyaddr() routine is available
1681  to look up networks by their C<IP> addresses.
1682  
1683  =item C<d_getnbyname>
1684  
1685  From F<d_getnbynm.U>:
1686  
1687  This variable conditionally defines the C<HAS_GETNETBYNAME> symbol, which
1688  indicates to the C program that the getnetbyname() routine is available
1689  to look up networks by their names.
1690  
1691  =item C<d_getnent>
1692  
1693  From F<d_getnent.U>:
1694  
1695  This variable conditionally defines C<HAS_GETNETENT> if getnetent() is
1696  available to look up network names in some data base or another.
1697  
1698  =item C<d_getnetbyaddr_r>
1699  
1700  From F<d_getnetbyaddr_r.U>:
1701  
1702  This variable conditionally defines the C<HAS_GETNETBYADDR_R> symbol,
1703  which indicates to the C program that the getnetbyaddr_r()
1704  routine is available.
1705  
1706  =item C<d_getnetbyname_r>
1707  
1708  From F<d_getnetbyname_r.U>:
1709  
1710  This variable conditionally defines the C<HAS_GETNETBYNAME_R> symbol,
1711  which indicates to the C program that the getnetbyname_r()
1712  routine is available.
1713  
1714  =item C<d_getnetent_r>
1715  
1716  From F<d_getnetent_r.U>:
1717  
1718  This variable conditionally defines the C<HAS_GETNETENT_R> symbol,
1719  which indicates to the C program that the getnetent_r()
1720  routine is available.
1721  
1722  =item C<d_getnetprotos>
1723  
1724  From F<d_getnetprotos.U>:
1725  
1726  This variable conditionally defines the C<HAS_GETNET_PROTOS> symbol,
1727  which indicates to the C program that <netdb.h> supplies
1728  prototypes for the various getnet*() functions.
1729  See also F<netdbtype.U> for probing for various netdb types.
1730  
1731  =item C<d_getpagsz>
1732  
1733  From F<d_getpagsz.U>:
1734  
1735  This variable conditionally defines C<HAS_GETPAGESIZE> if getpagesize()
1736  is available to get the system page size.
1737  
1738  =item C<d_getpbyname>
1739  
1740  From F<d_getprotby.U>:
1741  
1742  This variable conditionally defines the C<HAS_GETPROTOBYNAME>
1743  symbol, which indicates to the C program that the
1744  getprotobyname() routine is available to look up protocols
1745  by their name.
1746  
1747  =item C<d_getpbynumber>
1748  
1749  From F<d_getprotby.U>:
1750  
1751  This variable conditionally defines the C<HAS_GETPROTOBYNUMBER>
1752  symbol, which indicates to the C program that the
1753  getprotobynumber() routine is available to look up protocols
1754  by their number.
1755  
1756  =item C<d_getpent>
1757  
1758  From F<d_getpent.U>:
1759  
1760  This variable conditionally defines C<HAS_GETPROTOENT> if getprotoent() is
1761  available to look up protocols in some data base or another.
1762  
1763  =item C<d_getpgid>
1764  
1765  From F<d_getpgid.U>:
1766  
1767  This variable conditionally defines the C<HAS_GETPGID> symbol, which
1768  indicates to the C program that the getpgid(pid) function
1769  is available to get the process group id.
1770  
1771  =item C<d_getpgrp>
1772  
1773  From F<d_getpgrp.U>:
1774  
1775  This variable conditionally defines C<HAS_GETPGRP> if getpgrp() is
1776  available to get the current process group.
1777  
1778  =item C<d_getpgrp2>
1779  
1780  From F<d_getpgrp2.U>:
1781  
1782  This variable conditionally defines the HAS_GETPGRP2 symbol, which
1783  indicates to the C program that the getpgrp2() (as in F<DG/C<UX>>) routine
1784  is available to get the current process group.
1785  
1786  =item C<d_getppid>
1787  
1788  From F<d_getppid.U>:
1789  
1790  This variable conditionally defines the C<HAS_GETPPID> symbol, which
1791  indicates to the C program that the getppid() routine is available
1792  to get the parent process C<ID>.
1793  
1794  =item C<d_getprior>
1795  
1796  From F<d_getprior.U>:
1797  
1798  This variable conditionally defines C<HAS_GETPRIORITY> if getpriority()
1799  is available to get a process's priority.
1800  
1801  =item C<d_getprotobyname_r>
1802  
1803  From F<d_getprotobyname_r.U>:
1804  
1805  This variable conditionally defines the C<HAS_GETPROTOBYNAME_R> symbol,
1806  which indicates to the C program that the getprotobyname_r()
1807  routine is available.
1808  
1809  =item C<d_getprotobynumber_r>
1810  
1811  From F<d_getprotobynumber_r.U>:
1812  
1813  This variable conditionally defines the C<HAS_GETPROTOBYNUMBER_R> symbol,
1814  which indicates to the C program that the getprotobynumber_r()
1815  routine is available.
1816  
1817  =item C<d_getprotoent_r>
1818  
1819  From F<d_getprotoent_r.U>:
1820  
1821  This variable conditionally defines the C<HAS_GETPROTOENT_R> symbol,
1822  which indicates to the C program that the getprotoent_r()
1823  routine is available.
1824  
1825  =item C<d_getprotoprotos>
1826  
1827  From F<d_getprotoprotos.U>:
1828  
1829  This variable conditionally defines the C<HAS_GETPROTO_PROTOS> symbol,
1830  which indicates to the C program that <netdb.h> supplies
1831  prototypes for the various getproto*() functions.
1832  See also F<netdbtype.U> for probing for various netdb types.
1833  
1834  =item C<d_getprpwnam>
1835  
1836  From F<d_getprpwnam.U>:
1837  
1838  This variable conditionally defines C<HAS_GETPRPWNAM> if getprpwnam() is
1839  available to retrieve protected (shadow) password entries by name.
1840  
1841  =item C<d_getpwent>
1842  
1843  From F<d_getpwent.U>:
1844  
1845  This variable conditionally defines the C<HAS_GETPWENT> symbol, which
1846  indicates to the C program that the getpwent() routine is available
1847  for sequential access of the passwd database.
1848  
1849  =item C<d_getpwent_r>
1850  
1851  From F<d_getpwent_r.U>:
1852  
1853  This variable conditionally defines the C<HAS_GETPWENT_R> symbol,
1854  which indicates to the C program that the getpwent_r()
1855  routine is available.
1856  
1857  =item C<d_getpwnam_r>
1858  
1859  From F<d_getpwnam_r.U>:
1860  
1861  This variable conditionally defines the C<HAS_GETPWNAM_R> symbol,
1862  which indicates to the C program that the getpwnam_r()
1863  routine is available.
1864  
1865  =item C<d_getpwuid_r>
1866  
1867  From F<d_getpwuid_r.U>:
1868  
1869  This variable conditionally defines the C<HAS_GETPWUID_R> symbol,
1870  which indicates to the C program that the getpwuid_r()
1871  routine is available.
1872  
1873  =item C<d_getsbyname>
1874  
1875  From F<d_getsrvby.U>:
1876  
1877  This variable conditionally defines the C<HAS_GETSERVBYNAME>
1878  symbol, which indicates to the C program that the
1879  getservbyname() routine is available to look up services
1880  by their name.
1881  
1882  =item C<d_getsbyport>
1883  
1884  From F<d_getsrvby.U>:
1885  
1886  This variable conditionally defines the C<HAS_GETSERVBYPORT>
1887  symbol, which indicates to the C program that the
1888  getservbyport() routine is available to look up services
1889  by their port.
1890  
1891  =item C<d_getsent>
1892  
1893  From F<d_getsent.U>:
1894  
1895  This variable conditionally defines C<HAS_GETSERVENT> if getservent() is
1896  available to look up network services in some data base or another.
1897  
1898  =item C<d_getservbyname_r>
1899  
1900  From F<d_getservbyname_r.U>:
1901  
1902  This variable conditionally defines the C<HAS_GETSERVBYNAME_R> symbol,
1903  which indicates to the C program that the getservbyname_r()
1904  routine is available.
1905  
1906  =item C<d_getservbyport_r>
1907  
1908  From F<d_getservbyport_r.U>:
1909  
1910  This variable conditionally defines the C<HAS_GETSERVBYPORT_R> symbol,
1911  which indicates to the C program that the getservbyport_r()
1912  routine is available.
1913  
1914  =item C<d_getservent_r>
1915  
1916  From F<d_getservent_r.U>:
1917  
1918  This variable conditionally defines the C<HAS_GETSERVENT_R> symbol,
1919  which indicates to the C program that the getservent_r()
1920  routine is available.
1921  
1922  =item C<d_getservprotos>
1923  
1924  From F<d_getservprotos.U>:
1925  
1926  This variable conditionally defines the C<HAS_GETSERV_PROTOS> symbol,
1927  which indicates to the C program that <netdb.h> supplies
1928  prototypes for the various getserv*() functions.
1929  See also F<netdbtype.U> for probing for various netdb types.
1930  
1931  =item C<d_getspnam>
1932  
1933  From F<d_getspnam.U>:
1934  
1935  This variable conditionally defines C<HAS_GETSPNAM> if getspnam() is
1936  available to retrieve SysV shadow password entries by name.
1937  
1938  =item C<d_getspnam_r>
1939  
1940  From F<d_getspnam_r.U>:
1941  
1942  This variable conditionally defines the C<HAS_GETSPNAM_R> symbol,
1943  which indicates to the C program that the getspnam_r()
1944  routine is available.
1945  
1946  =item C<d_gettimeod>
1947  
1948  From F<d_ftime.U>:
1949  
1950  This variable conditionally defines the C<HAS_GETTIMEOFDAY> symbol, which
1951  indicates that the gettimeofday() system call exists (to obtain a
1952  sub-second accuracy clock). You should probably include <sys/resource.h>.
1953  
1954  =item C<d_gmtime_r>
1955  
1956  From F<d_gmtime_r.U>:
1957  
1958  This variable conditionally defines the C<HAS_GMTIME_R> symbol,
1959  which indicates to the C program that the gmtime_r()
1960  routine is available.
1961  
1962  =item C<d_gnulibc>
1963  
1964  From F<d_gnulibc.U>:
1965  
1966  Defined if we're dealing with the C<GNU> C Library.
1967  
1968  =item C<d_grpasswd>
1969  
1970  From F<i_grp.U>:
1971  
1972  This variable conditionally defines C<GRPASSWD>, which indicates
1973  that struct group in <grp.h> contains gr_passwd.
1974  
1975  =item C<d_hasmntopt>
1976  
1977  From F<d_hasmntopt.U>:
1978  
1979  This variable conditionally defines the C<HAS_HASMNTOPT> symbol, which
1980  indicates to the C program that the hasmntopt() routine is available
1981  to query the mount options of file systems.
1982  
1983  =item C<d_htonl>
1984  
1985  From F<d_htonl.U>:
1986  
1987  This variable conditionally defines C<HAS_HTONL> if htonl() and its
1988  friends are available to do network order byte swapping.
1989  
1990  =item C<d_ilogbl>
1991  
1992  From F<d_ilogbl.U>:
1993  
1994  This variable conditionally defines the C<HAS_ILOGBL> symbol, which
1995  indicates to the C program that the ilogbl() routine is available.
1996  If scalbnl is also present we can emulate frexpl.
1997  
1998  =item C<d_inc_version_list>
1999  
2000  From F<inc_version_list.U>:
2001  
2002  This variable conditionally defines C<PERL_INC_VERSION_LIST>.
2003  It is set to undef when C<PERL_INC_VERSION_LIST> is empty.
2004  
2005  =item C<d_index>
2006  
2007  From F<d_strchr.U>:
2008  
2009  This variable conditionally defines C<HAS_INDEX> if index() and
2010  rindex() are available for string searching.
2011  
2012  =item C<d_inetaton>
2013  
2014  From F<d_inetaton.U>:
2015  
2016  This variable conditionally defines the C<HAS_INET_ATON> symbol, which
2017  indicates to the C program that the inet_aton() function is available
2018  to parse C<IP> address C<dotted-quad> strings.
2019  
2020  =item C<d_int64_t>
2021  
2022  From F<d_int64_t.U>:
2023  
2024  This symbol will be defined if the C compiler supports int64_t.
2025  
2026  =item C<d_isascii>
2027  
2028  From F<d_isascii.U>:
2029  
2030  This variable conditionally defines the C<HAS_ISASCII> constant,
2031  which indicates to the C program that isascii() is available.
2032  
2033  =item C<d_isfinite>
2034  
2035  From F<d_isfinite.U>:
2036  
2037  This variable conditionally defines the C<HAS_ISFINITE> symbol, which
2038  indicates to the C program that the isfinite() routine is available.
2039  
2040  =item C<d_isinf>
2041  
2042  From F<d_isinf.U>:
2043  
2044  This variable conditionally defines the C<HAS_ISINF> symbol, which
2045  indicates to the C program that the isinf() routine is available.
2046  
2047  =item C<d_isnan>
2048  
2049  From F<d_isnan.U>:
2050  
2051  This variable conditionally defines the C<HAS_ISNAN> symbol, which
2052  indicates to the C program that the isnan() routine is available.
2053  
2054  =item C<d_isnanl>
2055  
2056  From F<d_isnanl.U>:
2057  
2058  This variable conditionally defines the C<HAS_ISNANL> symbol, which
2059  indicates to the C program that the isnanl() routine is available.
2060  
2061  =item C<d_killpg>
2062  
2063  From F<d_killpg.U>:
2064  
2065  This variable conditionally defines the C<HAS_KILLPG> symbol, which
2066  indicates to the C program that the killpg() routine is available
2067  to kill process groups.
2068  
2069  =item C<d_lchown>
2070  
2071  From F<d_lchown.U>:
2072  
2073  This variable conditionally defines the C<HAS_LCHOWN> symbol, which
2074  indicates to the C program that the lchown() routine is available
2075  to operate on a symbolic link (instead of following the link).
2076  
2077  =item C<d_ldbl_dig>
2078  
2079  From F<d_ldbl_dig.U>:
2080  
2081  This variable conditionally defines d_ldbl_dig if this system's
2082  header files provide C<LDBL_DIG>, which is the number of significant
2083  digits in a long double precision number.
2084  
2085  =item C<d_libm_lib_version>
2086  
2087  From F<d_libm_lib_version.U>:
2088  
2089  This variable conditionally defines the C<LIBM_LIB_VERSION> symbol,
2090  which indicates to the C program that F<math.h> defines C<_LIB_VERSION>
2091  being available in libm
2092  
2093  =item C<d_link>
2094  
2095  From F<d_link.U>:
2096  
2097  This variable conditionally defines C<HAS_LINK> if link() is
2098  available to create hard links.
2099  
2100  =item C<d_localtime_r>
2101  
2102  From F<d_localtime_r.U>:
2103  
2104  This variable conditionally defines the C<HAS_LOCALTIME_R> symbol,
2105  which indicates to the C program that the localtime_r()
2106  routine is available.
2107  
2108  =item C<d_localtime_r_needs_tzset>
2109  
2110  From F<d_localtime_r.U>:
2111  
2112  This variable conditionally defines the C<LOCALTIME_R_NEEDS_TZSET>
2113  symbol, which makes us call tzset before localtime_r()
2114  
2115  =item C<d_locconv>
2116  
2117  From F<d_locconv.U>:
2118  
2119  This variable conditionally defines C<HAS_LOCALECONV> if localeconv() is
2120  available for numeric and monetary formatting conventions.
2121  
2122  =item C<d_lockf>
2123  
2124  From F<d_lockf.U>:
2125  
2126  This variable conditionally defines C<HAS_LOCKF> if lockf() is
2127  available to do file locking.
2128  
2129  =item C<d_longdbl>
2130  
2131  From F<d_longdbl.U>:
2132  
2133  This variable conditionally defines C<HAS_LONG_DOUBLE> if
2134  the long double type is supported.
2135  
2136  =item C<d_longlong>
2137  
2138  From F<d_longlong.U>:
2139  
2140  This variable conditionally defines C<HAS_LONG_LONG> if
2141  the long long type is supported.
2142  
2143  =item C<d_lseekproto>
2144  
2145  From F<d_lseekproto.U>:
2146  
2147  This variable conditionally defines the C<HAS_LSEEK_PROTO> symbol,
2148  which indicates to the C program that the system provides
2149  a prototype for the lseek() function.  Otherwise, it is
2150  up to the program to supply one.
2151  
2152  =item C<d_lstat>
2153  
2154  From F<d_lstat.U>:
2155  
2156  This variable conditionally defines C<HAS_LSTAT> if lstat() is
2157  available to do file stats on symbolic links.
2158  
2159  =item C<d_madvise>
2160  
2161  From F<d_madvise.U>:
2162  
2163  This variable conditionally defines C<HAS_MADVISE> if madvise() is
2164  available to map a file into memory.
2165  
2166  =item C<d_malloc_good_size>
2167  
2168  From F<d_malloc_size.U>:
2169  
2170  This symbol, if defined, indicates that the malloc_good_size
2171  routine is available for use.
2172  
2173  =item C<d_malloc_size>
2174  
2175  From F<d_malloc_size.U>:
2176  
2177  This symbol, if defined, indicates that the malloc_size
2178  routine is available for use.
2179  
2180  =item C<d_mblen>
2181  
2182  From F<d_mblen.U>:
2183  
2184  This variable conditionally defines the C<HAS_MBLEN> symbol, which
2185  indicates to the C program that the mblen() routine is available
2186  to find the number of bytes in a multibye character.
2187  
2188  =item C<d_mbstowcs>
2189  
2190  From F<d_mbstowcs.U>:
2191  
2192  This variable conditionally defines the C<HAS_MBSTOWCS> symbol, which
2193  indicates to the C program that the mbstowcs() routine is available
2194  to convert a multibyte string into a wide character string.
2195  
2196  =item C<d_mbtowc>
2197  
2198  From F<d_mbtowc.U>:
2199  
2200  This variable conditionally defines the C<HAS_MBTOWC> symbol, which
2201  indicates to the C program that the mbtowc() routine is available
2202  to convert multibyte to a wide character.
2203  
2204  =item C<d_memchr>
2205  
2206  From F<d_memchr.U>:
2207  
2208  This variable conditionally defines the C<HAS_MEMCHR> symbol, which
2209  indicates to the C program that the memchr() routine is available
2210  to locate characters within a C string.
2211  
2212  =item C<d_memcmp>
2213  
2214  From F<d_memcmp.U>:
2215  
2216  This variable conditionally defines the C<HAS_MEMCMP> symbol, which
2217  indicates to the C program that the memcmp() routine is available
2218  to compare blocks of memory.
2219  
2220  =item C<d_memcpy>
2221  
2222  From F<d_memcpy.U>:
2223  
2224  This variable conditionally defines the C<HAS_MEMCPY> symbol, which
2225  indicates to the C program that the memcpy() routine is available
2226  to copy blocks of memory.
2227  
2228  =item C<d_memmove>
2229  
2230  From F<d_memmove.U>:
2231  
2232  This variable conditionally defines the C<HAS_MEMMOVE> symbol, which
2233  indicates to the C program that the memmove() routine is available
2234  to copy potentatially overlapping blocks of memory.
2235  
2236  =item C<d_memset>
2237  
2238  From F<d_memset.U>:
2239  
2240  This variable conditionally defines the C<HAS_MEMSET> symbol, which
2241  indicates to the C program that the memset() routine is available
2242  to set blocks of memory.
2243  
2244  =item C<d_mkdir>
2245  
2246  From F<d_mkdir.U>:
2247  
2248  This variable conditionally defines the C<HAS_MKDIR> symbol, which
2249  indicates to the C program that the mkdir() routine is available
2250  to create F<directories.>.
2251  
2252  =item C<d_mkdtemp>
2253  
2254  From F<d_mkdtemp.U>:
2255  
2256  This variable conditionally defines the C<HAS_MKDTEMP> symbol, which
2257  indicates to the C program that the mkdtemp() routine is available
2258  to exclusively create a uniquely named temporary directory.
2259  
2260  =item C<d_mkfifo>
2261  
2262  From F<d_mkfifo.U>:
2263  
2264  This variable conditionally defines the C<HAS_MKFIFO> symbol, which
2265  indicates to the C program that the mkfifo() routine is available.
2266  
2267  =item C<d_mkstemp>
2268  
2269  From F<d_mkstemp.U>:
2270  
2271  This variable conditionally defines the C<HAS_MKSTEMP> symbol, which
2272  indicates to the C program that the mkstemp() routine is available
2273  to exclusively create and open a uniquely named temporary file.
2274  
2275  =item C<d_mkstemps>
2276  
2277  From F<d_mkstemps.U>:
2278  
2279  This variable conditionally defines the C<HAS_MKSTEMPS> symbol, which
2280  indicates to the C program that the mkstemps() routine is available
2281  to exclusively create and open a uniquely named (with a suffix)
2282  temporary file.
2283  
2284  =item C<d_mktime>
2285  
2286  From F<d_mktime.U>:
2287  
2288  This variable conditionally defines the C<HAS_MKTIME> symbol, which
2289  indicates to the C program that the mktime() routine is available.
2290  
2291  =item C<d_mmap>
2292  
2293  From F<d_mmap.U>:
2294  
2295  This variable conditionally defines C<HAS_MMAP> if mmap() is
2296  available to map a file into memory.
2297  
2298  =item C<d_modfl>
2299  
2300  From F<d_modfl.U>:
2301  
2302  This variable conditionally defines the C<HAS_MODFL> symbol, which
2303  indicates to the C program that the modfl() routine is available.
2304  
2305  =item C<d_modfl_pow32_bug>
2306  
2307  From F<d_modfl.U>:
2308  
2309  This variable conditionally defines the HAS_MODFL_POW32_BUG symbol,
2310  which indicates that modfl() is broken for long doubles >= pow(2, 32).
2311  For example from 4294967303.150000 one would get 4294967302.000000
2312  and 1.150000.  The bug has been seen in certain versions of glibc,
2313  release 2.2.2 is known to be okay.
2314  
2315  =item C<d_modflproto>
2316  
2317  From F<d_modfl.U>:
2318  
2319  This symbol, if defined, indicates that the system provides
2320  a prototype for the modfl() function.  Otherwise, it is up
2321  to the program to supply one.  C99 says it should be
2322  long double modfl(long double, long double *);
2323  
2324  =item C<d_mprotect>
2325  
2326  From F<d_mprotect.U>:
2327  
2328  This variable conditionally defines C<HAS_MPROTECT> if mprotect() is
2329  available to modify the access protection of a memory mapped file.
2330  
2331  =item C<d_msg>
2332  
2333  From F<d_msg.U>:
2334  
2335  This variable conditionally defines the C<HAS_MSG> symbol, which
2336  indicates that the entire msg*(2) library is present.
2337  
2338  =item C<d_msg_ctrunc>
2339  
2340  From F<d_socket.U>:
2341  
2342  This variable conditionally defines the C<HAS_MSG_CTRUNC> symbol,
2343  which indicates that the C<MSG_CTRUNC> is available.  #ifdef is
2344  not enough because it may be an enum, glibc has been known to do this.
2345  
2346  =item C<d_msg_dontroute>
2347  
2348  From F<d_socket.U>:
2349  
2350  This variable conditionally defines the C<HAS_MSG_DONTROUTE> symbol,
2351  which indicates that the C<MSG_DONTROUTE> is available.  #ifdef is
2352  not enough because it may be an enum, glibc has been known to do this.
2353  
2354  =item C<d_msg_oob>
2355  
2356  From F<d_socket.U>:
2357  
2358  This variable conditionally defines the C<HAS_MSG_OOB> symbol,
2359  which indicates that the C<MSG_OOB> is available.  #ifdef is
2360  not enough because it may be an enum, glibc has been known to do this.
2361  
2362  =item C<d_msg_peek>
2363  
2364  From F<d_socket.U>:
2365  
2366  This variable conditionally defines the C<HAS_MSG_PEEK> symbol,
2367  which indicates that the C<MSG_PEEK> is available.  #ifdef is
2368  not enough because it may be an enum, glibc has been known to do this.
2369  
2370  =item C<d_msg_proxy>
2371  
2372  From F<d_socket.U>:
2373  
2374  This variable conditionally defines the C<HAS_MSG_PROXY> symbol,
2375  which indicates that the C<MSG_PROXY> is available.  #ifdef is
2376  not enough because it may be an enum, glibc has been known to do this.
2377  
2378  =item C<d_msgctl>
2379  
2380  From F<d_msgctl.U>:
2381  
2382  This variable conditionally defines the C<HAS_MSGCTL> symbol, which
2383  indicates to the C program that the msgctl() routine is available.
2384  
2385  =item C<d_msgget>
2386  
2387  From F<d_msgget.U>:
2388  
2389  This variable conditionally defines the C<HAS_MSGGET> symbol, which
2390  indicates to the C program that the msgget() routine is available.
2391  
2392  =item C<d_msghdr_s>
2393  
2394  From F<d_msghdr_s.U>:
2395  
2396  This variable conditionally defines the C<HAS_STRUCT_MSGHDR> symbol,
2397  which indicates that the struct msghdr is supported.
2398  
2399  =item C<d_msgrcv>
2400  
2401  From F<d_msgrcv.U>:
2402  
2403  This variable conditionally defines the C<HAS_MSGRCV> symbol, which
2404  indicates to the C program that the msgrcv() routine is available.
2405  
2406  =item C<d_msgsnd>
2407  
2408  From F<d_msgsnd.U>:
2409  
2410  This variable conditionally defines the C<HAS_MSGSND> symbol, which
2411  indicates to the C program that the msgsnd() routine is available.
2412  
2413  =item C<d_msync>
2414  
2415  From F<d_msync.U>:
2416  
2417  This variable conditionally defines C<HAS_MSYNC> if msync() is
2418  available to synchronize a mapped file.
2419  
2420  =item C<d_munmap>
2421  
2422  From F<d_munmap.U>:
2423  
2424  This variable conditionally defines C<HAS_MUNMAP> if munmap() is
2425  available to unmap a region mapped by mmap().
2426  
2427  =item C<d_mymalloc>
2428  
2429  From F<mallocsrc.U>:
2430  
2431  This variable conditionally defines C<MYMALLOC> in case other parts
2432  of the source want to take special action if C<MYMALLOC> is used.
2433  This may include different sorts of profiling or error detection.
2434  
2435  =item C<d_nice>
2436  
2437  From F<d_nice.U>:
2438  
2439  This variable conditionally defines the C<HAS_NICE> symbol, which
2440  indicates to the C program that the nice() routine is available.
2441  
2442  =item C<d_nl_langinfo>
2443  
2444  From F<d_nl_langinfo.U>:
2445  
2446  This variable conditionally defines the C<HAS_NL_LANGINFO> symbol, which
2447  indicates to the C program that the nl_langinfo() routine is available.
2448  
2449  =item C<d_nv_preserves_uv>
2450  
2451  From F<perlxv.U>:
2452  
2453  This variable indicates whether a variable of type nvtype
2454  can preserve all the bits a variable of type uvtype.
2455  
2456  =item C<d_nv_zero_is_allbits_zero>
2457  
2458  From F<perlxv.U>:
2459  
2460  This variable indicates whether a variable of type nvtype
2461  stores 0.0 in memory as all bits zero.
2462  
2463  =item C<d_off64_t>
2464  
2465  From F<d_off64_t.U>:
2466  
2467  This symbol will be defined if the C compiler supports off64_t.
2468  
2469  =item C<d_old_pthread_create_joinable>
2470  
2471  From F<d_pthrattrj.U>:
2472  
2473  This variable conditionally defines pthread_create_joinable.
2474  undef if F<pthread.h> defines C<PTHREAD_CREATE_JOINABLE>.
2475  
2476  =item C<d_oldpthreads>
2477  
2478  From F<usethreads.U>:
2479  
2480  This variable conditionally defines the C<OLD_PTHREADS_API> symbol,
2481  and indicates that Perl should be built to use the old
2482  draft C<POSIX> threads C<API>.  This is only potentially meaningful if
2483  usethreads is set.
2484  
2485  =item C<d_oldsock>
2486  
2487  From F<d_socket.U>:
2488  
2489  This variable conditionally defines the C<OLDSOCKET> symbol, which
2490  indicates that the C<BSD> socket interface is based on 4.1c and not 4.2.
2491  
2492  =item C<d_open3>
2493  
2494  From F<d_open3.U>:
2495  
2496  This variable conditionally defines the HAS_OPEN3 manifest constant,
2497  which indicates to the C program that the 3 argument version of
2498  the open(2) function is available.
2499  
2500  =item C<d_pathconf>
2501  
2502  From F<d_pathconf.U>:
2503  
2504  This variable conditionally defines the C<HAS_PATHCONF> symbol, which
2505  indicates to the C program that the pathconf() routine is available
2506  to determine file-system related limits and options associated
2507  with a given filename.
2508  
2509  =item C<d_pause>
2510  
2511  From F<d_pause.U>:
2512  
2513  This variable conditionally defines the C<HAS_PAUSE> symbol, which
2514  indicates to the C program that the pause() routine is available
2515  to suspend a process until a signal is received.
2516  
2517  =item C<d_perl_otherlibdirs>
2518  
2519  From F<otherlibdirs.U>:
2520  
2521  This variable conditionally defines C<PERL_OTHERLIBDIRS>, which
2522  contains a colon-separated set of paths for the perl binary to
2523  include in @C<INC>.  See also otherlibdirs.
2524  
2525  =item C<d_phostname>
2526  
2527  From F<d_gethname.U>:
2528  
2529  This variable conditionally defines the C<HAS_PHOSTNAME> symbol, which
2530  contains the shell command which, when fed to popen(), may be
2531  used to derive the host name.
2532  
2533  =item C<d_pipe>
2534  
2535  From F<d_pipe.U>:
2536  
2537  This variable conditionally defines the C<HAS_PIPE> symbol, which
2538  indicates to the C program that the pipe() routine is available
2539  to create an inter-process channel.
2540  
2541  =item C<d_poll>
2542  
2543  From F<d_poll.U>:
2544  
2545  This variable conditionally defines the C<HAS_POLL> symbol, which
2546  indicates to the C program that the poll() routine is available
2547  to poll active file descriptors.
2548  
2549  =item C<d_portable>
2550  
2551  From F<d_portable.U>:
2552  
2553  This variable conditionally defines the C<PORTABLE> symbol, which
2554  indicates to the C program that it should not assume that it is
2555  running on the machine it was compiled on.
2556  
2557  =item C<d_PRId64>
2558  
2559  From F<quadfio.U>:
2560  
2561  This variable conditionally defines the PERL_PRId64 symbol, which
2562  indiciates that stdio has a symbol to print 64-bit decimal numbers.
2563  
2564  =item C<d_PRIeldbl>
2565  
2566  From F<longdblfio.U>:
2567  
2568  This variable conditionally defines the PERL_PRIfldbl symbol, which
2569  indiciates that stdio has a symbol to print long doubles.
2570  
2571  =item C<d_PRIEUldbl>
2572  
2573  From F<longdblfio.U>:
2574  
2575  This variable conditionally defines the PERL_PRIfldbl symbol, which
2576  indiciates that stdio has a symbol to print long doubles.
2577  The C<U> in the name is to separate this from d_PRIeldbl so that even
2578  case-blind systems can see the difference.
2579  
2580  =item C<d_PRIfldbl>
2581  
2582  From F<longdblfio.U>:
2583  
2584  This variable conditionally defines the PERL_PRIfldbl symbol, which
2585  indiciates that stdio has a symbol to print long doubles.
2586  
2587  =item C<d_PRIFUldbl>
2588  
2589  From F<longdblfio.U>:
2590  
2591  This variable conditionally defines the PERL_PRIfldbl symbol, which
2592  indiciates that stdio has a symbol to print long doubles.
2593  The C<U> in the name is to separate this from d_PRIfldbl so that even
2594  case-blind systems can see the difference.
2595  
2596  =item C<d_PRIgldbl>
2597  
2598  From F<longdblfio.U>:
2599  
2600  This variable conditionally defines the PERL_PRIfldbl symbol, which
2601  indiciates that stdio has a symbol to print long doubles.
2602  
2603  =item C<d_PRIGUldbl>
2604  
2605  From F<longdblfio.U>:
2606  
2607  This variable conditionally defines the PERL_PRIfldbl symbol, which
2608  indiciates that stdio has a symbol to print long doubles.
2609  The C<U> in the name is to separate this from d_PRIgldbl so that even
2610  case-blind systems can see the difference.
2611  
2612  =item C<d_PRIi64>
2613  
2614  From F<quadfio.U>:
2615  
2616  This variable conditionally defines the PERL_PRIi64 symbol, which
2617  indiciates that stdio has a symbol to print 64-bit decimal numbers.
2618  
2619  =item C<d_printf_format_null>
2620  
2621  From F<d_attribut.U>:
2622  
2623  This variable conditionally defines C<PRINTF_FORMAT_NULL_OK>, which
2624  indicates the C compiler allows printf-like formats to be null.
2625  
2626  =item C<d_PRIo64>
2627  
2628  From F<quadfio.U>:
2629  
2630  This variable conditionally defines the PERL_PRIo64 symbol, which
2631  indiciates that stdio has a symbol to print 64-bit octal numbers.
2632  
2633  =item C<d_PRIu64>
2634  
2635  From F<quadfio.U>:
2636  
2637  This variable conditionally defines the PERL_PRIu64 symbol, which
2638  indiciates that stdio has a symbol to print 64-bit unsigned decimal
2639  numbers.
2640  
2641  =item C<d_PRIx64>
2642  
2643  From F<quadfio.U>:
2644  
2645  This variable conditionally defines the PERL_PRIx64 symbol, which
2646  indiciates that stdio has a symbol to print 64-bit hexadecimal numbers.
2647  
2648  =item C<d_PRIXU64>
2649  
2650  From F<quadfio.U>:
2651  
2652  This variable conditionally defines the PERL_PRIXU64 symbol, which
2653  indiciates that stdio has a symbol to print 64-bit hExADECimAl numbers.
2654  The C<U> in the name is to separate this from d_PRIx64 so that even
2655  case-blind systems can see the difference.
2656  
2657  =item C<d_procselfexe>
2658  
2659  From F<d_procselfexe.U>:
2660  
2661  Defined if $procselfexe is symlink to the absolute
2662  pathname of the executing program.
2663  
2664  =item C<d_pseudofork>
2665  
2666  From F<d_vfork.U>:
2667  
2668  This variable conditionally defines the C<HAS_PSEUDOFORK> symbol,
2669  which indicates that an emulation of the fork routine is available.
2670  
2671  =item C<d_pthread_atfork>
2672  
2673  From F<d_pthread_atfork.U>:
2674  
2675  This variable conditionally defines the C<HAS_PTHREAD_ATFORK> symbol,
2676  which indicates to the C program that the pthread_atfork()
2677  routine is available.
2678  
2679  =item C<d_pthread_attr_setscope>
2680  
2681  From F<d_pthread_attr_ss.U>:
2682  
2683  This variable conditionally defines C<HAS_PTHREAD_ATTR_SETSCOPE> if
2684  pthread_attr_setscope() is available to set the contention scope
2685  attribute of a thread attribute object.
2686  
2687  =item C<d_pthread_yield>
2688  
2689  From F<d_pthread_y.U>:
2690  
2691  This variable conditionally defines the C<HAS_PTHREAD_YIELD>
2692  symbol if the pthread_yield routine is available to yield
2693  the execution of the current thread.
2694  
2695  =item C<d_pwage>
2696  
2697  From F<i_pwd.U>:
2698  
2699  This variable conditionally defines C<PWAGE>, which indicates
2700  that struct passwd contains pw_age.
2701  
2702  =item C<d_pwchange>
2703  
2704  From F<i_pwd.U>:
2705  
2706  This variable conditionally defines C<PWCHANGE>, which indicates
2707  that struct passwd contains pw_change.
2708  
2709  =item C<d_pwclass>
2710  
2711  From F<i_pwd.U>:
2712  
2713  This variable conditionally defines C<PWCLASS>, which indicates
2714  that struct passwd contains pw_class.
2715  
2716  =item C<d_pwcomment>
2717  
2718  From F<i_pwd.U>:
2719  
2720  This variable conditionally defines C<PWCOMMENT>, which indicates
2721  that struct passwd contains pw_comment.
2722  
2723  =item C<d_pwexpire>
2724  
2725  From F<i_pwd.U>:
2726  
2727  This variable conditionally defines C<PWEXPIRE>, which indicates
2728  that struct passwd contains pw_expire.
2729  
2730  =item C<d_pwgecos>
2731  
2732  From F<i_pwd.U>:
2733  
2734  This variable conditionally defines C<PWGECOS>, which indicates
2735  that struct passwd contains pw_gecos.
2736  
2737  =item C<d_pwpasswd>
2738  
2739  From F<i_pwd.U>:
2740  
2741  This variable conditionally defines C<PWPASSWD>, which indicates
2742  that struct passwd contains pw_passwd.
2743  
2744  =item C<d_pwquota>
2745  
2746  From F<i_pwd.U>:
2747  
2748  This variable conditionally defines C<PWQUOTA>, which indicates
2749  that struct passwd contains pw_quota.
2750  
2751  =item C<d_qgcvt>
2752  
2753  From F<d_qgcvt.U>:
2754  
2755  This variable conditionally defines the C<HAS_QGCVT> symbol, which
2756  indicates to the C program that the qgcvt() routine is available.
2757  
2758  =item C<d_quad>
2759  
2760  From F<quadtype.U>:
2761  
2762  This variable, if defined, tells that there's a 64-bit integer type,
2763  quadtype.
2764  
2765  =item C<d_random_r>
2766  
2767  From F<d_random_r.U>:
2768  
2769  This variable conditionally defines the C<HAS_RANDOM_R> symbol,
2770  which indicates to the C program that the random_r()
2771  routine is available.
2772  
2773  =item C<d_readdir>
2774  
2775  From F<d_readdir.U>:
2776  
2777  This variable conditionally defines C<HAS_READDIR> if readdir() is
2778  available to read directory entries.
2779  
2780  =item C<d_readdir64_r>
2781  
2782  From F<d_readdir64_r.U>:
2783  
2784  This variable conditionally defines the HAS_READDIR64_R symbol,
2785  which indicates to the C program that the readdir64_r()
2786  routine is available.
2787  
2788  =item C<d_readdir_r>
2789  
2790  From F<d_readdir_r.U>:
2791  
2792  This variable conditionally defines the C<HAS_READDIR_R> symbol,
2793  which indicates to the C program that the readdir_r()
2794  routine is available.
2795  
2796  =item C<d_readlink>
2797  
2798  From F<d_readlink.U>:
2799  
2800  This variable conditionally defines the C<HAS_READLINK> symbol, which
2801  indicates to the C program that the readlink() routine is available
2802  to read the value of a symbolic link.
2803  
2804  =item C<d_readv>
2805  
2806  From F<d_readv.U>:
2807  
2808  This variable conditionally defines the C<HAS_READV> symbol, which
2809  indicates to the C program that the readv() routine is available.
2810  
2811  =item C<d_recvmsg>
2812  
2813  From F<d_recvmsg.U>:
2814  
2815  This variable conditionally defines the C<HAS_RECVMSG> symbol, which
2816  indicates to the C program that the recvmsg() routine is available.
2817  
2818  =item C<d_rename>
2819  
2820  From F<d_rename.U>:
2821  
2822  This variable conditionally defines the C<HAS_RENAME> symbol, which
2823  indicates to the C program that the rename() routine is available
2824  to rename files.
2825  
2826  =item C<d_rewinddir>
2827  
2828  From F<d_readdir.U>:
2829  
2830  This variable conditionally defines C<HAS_REWINDDIR> if rewinddir() is
2831  available.
2832  
2833  =item C<d_rmdir>
2834  
2835  From F<d_rmdir.U>:
2836  
2837  This variable conditionally defines C<HAS_RMDIR> if rmdir() is
2838  available to remove directories.
2839  
2840  =item C<d_safebcpy>
2841  
2842  From F<d_safebcpy.U>:
2843  
2844  This variable conditionally defines the C<HAS_SAFE_BCOPY> symbol if
2845  the bcopy() routine can do overlapping copies.  Normally, you
2846  should probably use memmove().
2847  
2848  =item C<d_safemcpy>
2849  
2850  From F<d_safemcpy.U>:
2851  
2852  This variable conditionally defines the C<HAS_SAFE_MEMCPY> symbol if
2853  the memcpy() routine can do overlapping copies.
2854  For overlapping copies, memmove() should be used, if available.
2855  
2856  =item C<d_sanemcmp>
2857  
2858  From F<d_sanemcmp.U>:
2859  
2860  This variable conditionally defines the C<HAS_SANE_MEMCMP> symbol if
2861  the memcpy() routine is available and can be used to compare relative
2862  magnitudes of chars with their high bits set.
2863  
2864  =item C<d_sbrkproto>
2865  
2866  From F<d_sbrkproto.U>:
2867  
2868  This variable conditionally defines the C<HAS_SBRK_PROTO> symbol,
2869  which indicates to the C program that the system provides
2870  a prototype for the sbrk() function.  Otherwise, it is
2871  up to the program to supply one.
2872  
2873  =item C<d_scalbnl>
2874  
2875  From F<d_scalbnl.U>:
2876  
2877  This variable conditionally defines the C<HAS_SCALBNL> symbol, which
2878  indicates to the C program that the scalbnl() routine is available.
2879  If ilogbl is also present we can emulate frexpl.
2880  
2881  =item C<d_sched_yield>
2882  
2883  From F<d_pthread_y.U>:
2884  
2885  This variable conditionally defines the C<HAS_SCHED_YIELD>
2886  symbol if the sched_yield routine is available to yield
2887  the execution of the current thread.
2888  
2889  =item C<d_scm_rights>
2890  
2891  From F<d_socket.U>:
2892  
2893  This variable conditionally defines the C<HAS_SCM_RIGHTS> symbol,
2894  which indicates that the C<SCM_RIGHTS> is available.  #ifdef is
2895  not enough because it may be an enum, glibc has been known to do this.
2896  
2897  =item C<d_SCNfldbl>
2898  
2899  From F<longdblfio.U>:
2900  
2901  This variable conditionally defines the PERL_PRIfldbl symbol, which
2902  indiciates that stdio has a symbol to scan long doubles.
2903  
2904  =item C<d_seekdir>
2905  
2906  From F<d_readdir.U>:
2907  
2908  This variable conditionally defines C<HAS_SEEKDIR> if seekdir() is
2909  available.
2910  
2911  =item C<d_select>
2912  
2913  From F<d_select.U>:
2914  
2915  This variable conditionally defines C<HAS_SELECT> if select() is
2916  available to select active file descriptors. A <sys/time.h>
2917  inclusion may be necessary for the timeout field.
2918  
2919  =item C<d_sem>
2920  
2921  From F<d_sem.U>:
2922  
2923  This variable conditionally defines the C<HAS_SEM> symbol, which
2924  indicates that the entire sem*(2) library is present.
2925  
2926  =item C<d_semctl>
2927  
2928  From F<d_semctl.U>:
2929  
2930  This variable conditionally defines the C<HAS_SEMCTL> symbol, which
2931  indicates to the C program that the semctl() routine is available.
2932  
2933  =item C<d_semctl_semid_ds>
2934  
2935  From F<d_union_semun.U>:
2936  
2937  This variable conditionally defines C<USE_SEMCTL_SEMID_DS>, which
2938  indicates that struct semid_ds * is to be used for semctl C<IPC_STAT>.
2939  
2940  =item C<d_semctl_semun>
2941  
2942  From F<d_union_semun.U>:
2943  
2944  This variable conditionally defines C<USE_SEMCTL_SEMUN>, which
2945  indicates that union semun is to be used for semctl C<IPC_STAT>.
2946  
2947  =item C<d_semget>
2948  
2949  From F<d_semget.U>:
2950  
2951  This variable conditionally defines the C<HAS_SEMGET> symbol, which
2952  indicates to the C program that the semget() routine is available.
2953  
2954  =item C<d_semop>
2955  
2956  From F<d_semop.U>:
2957  
2958  This variable conditionally defines the C<HAS_SEMOP> symbol, which
2959  indicates to the C program that the semop() routine is available.
2960  
2961  =item C<d_sendmsg>
2962  
2963  From F<d_sendmsg.U>:
2964  
2965  This variable conditionally defines the C<HAS_SENDMSG> symbol, which
2966  indicates to the C program that the sendmsg() routine is available.
2967  
2968  =item C<d_setegid>
2969  
2970  From F<d_setegid.U>:
2971  
2972  This variable conditionally defines the C<HAS_SETEGID> symbol, which
2973  indicates to the C program that the setegid() routine is available
2974  to change the effective gid of the current program.
2975  
2976  =item C<d_seteuid>
2977  
2978  From F<d_seteuid.U>:
2979  
2980  This variable conditionally defines the C<HAS_SETEUID> symbol, which
2981  indicates to the C program that the seteuid() routine is available
2982  to change the effective uid of the current program.
2983  
2984  =item C<d_setgrent>
2985  
2986  From F<d_setgrent.U>:
2987  
2988  This variable conditionally defines the C<HAS_SETGRENT> symbol, which
2989  indicates to the C program that the setgrent() routine is available
2990  for initializing sequential access to the group database.
2991  
2992  =item C<d_setgrent_r>
2993  
2994  From F<d_setgrent_r.U>:
2995  
2996  This variable conditionally defines the C<HAS_SETGRENT_R> symbol,
2997  which indicates to the C program that the setgrent_r()
2998  routine is available.
2999  
3000  =item C<d_setgrps>
3001  
3002  From F<d_setgrps.U>:
3003  
3004  This variable conditionally defines the C<HAS_SETGROUPS> symbol, which
3005  indicates to the C program that the setgroups() routine is available
3006  to set the list of process groups.
3007  
3008  =item C<d_sethent>
3009  
3010  From F<d_sethent.U>:
3011  
3012  This variable conditionally defines C<HAS_SETHOSTENT> if sethostent() is
3013  available.
3014  
3015  =item C<d_sethostent_r>
3016  
3017  From F<d_sethostent_r.U>:
3018  
3019  This variable conditionally defines the C<HAS_SETHOSTENT_R> symbol,
3020  which indicates to the C program that the sethostent_r()
3021  routine is available.
3022  
3023  =item C<d_setitimer>
3024  
3025  From F<d_setitimer.U>:
3026  
3027  This variable conditionally defines the C<HAS_SETITIMER> symbol, which
3028  indicates to the C program that the setitimer() routine is available.
3029  
3030  =item C<d_setlinebuf>
3031  
3032  From F<d_setlnbuf.U>:
3033  
3034  This variable conditionally defines the C<HAS_SETLINEBUF> symbol, which
3035  indicates to the C program that the setlinebuf() routine is available
3036  to change stderr or stdout from block-buffered or unbuffered to a
3037  line-buffered mode.
3038  
3039  =item C<d_setlocale>
3040  
3041  From F<d_setlocale.U>:
3042  
3043  This variable conditionally defines C<HAS_SETLOCALE> if setlocale() is
3044  available to handle locale-specific ctype implementations.
3045  
3046  =item C<d_setlocale_r>
3047  
3048  From F<d_setlocale_r.U>:
3049  
3050  This variable conditionally defines the C<HAS_SETLOCALE_R> symbol,
3051  which indicates to the C program that the setlocale_r()
3052  routine is available.
3053  
3054  =item C<d_setnent>
3055  
3056  From F<d_setnent.U>:
3057  
3058  This variable conditionally defines C<HAS_SETNETENT> if setnetent() is
3059  available.
3060  
3061  =item C<d_setnetent_r>
3062  
3063  From F<d_setnetent_r.U>:
3064  
3065  This variable conditionally defines the C<HAS_SETNETENT_R> symbol,
3066  which indicates to the C program that the setnetent_r()
3067  routine is available.
3068  
3069  =item C<d_setpent>
3070  
3071  From F<d_setpent.U>:
3072  
3073  This variable conditionally defines C<HAS_SETPROTOENT> if setprotoent() is
3074  available.
3075  
3076  =item C<d_setpgid>
3077  
3078  From F<d_setpgid.U>:
3079  
3080  This variable conditionally defines the C<HAS_SETPGID> symbol if the
3081  setpgid(pid, gpid) function is available to set process group C<ID>.
3082  
3083  =item C<d_setpgrp>
3084  
3085  From F<d_setpgrp.U>:
3086  
3087  This variable conditionally defines C<HAS_SETPGRP> if setpgrp() is
3088  available to set the current process group.
3089  
3090  =item C<d_setpgrp2>
3091  
3092  From F<d_setpgrp2.U>:
3093  
3094  This variable conditionally defines the HAS_SETPGRP2 symbol, which
3095  indicates to the C program that the setpgrp2() (as in F<DG/C<UX>>) routine
3096  is available to set the current process group.
3097  
3098  =item C<d_setprior>
3099  
3100  From F<d_setprior.U>:
3101  
3102  This variable conditionally defines C<HAS_SETPRIORITY> if setpriority()
3103  is available to set a process's priority.
3104  
3105  =item C<d_setproctitle>
3106  
3107  From F<d_setproctitle.U>:
3108  
3109  This variable conditionally defines the C<HAS_SETPROCTITLE> symbol,
3110  which indicates to the C program that the setproctitle() routine
3111  is available.
3112  
3113  =item C<d_setprotoent_r>
3114  
3115  From F<d_setprotoent_r.U>:
3116  
3117  This variable conditionally defines the C<HAS_SETPROTOENT_R> symbol,
3118  which indicates to the C program that the setprotoent_r()
3119  routine is available.
3120  
3121  =item C<d_setpwent>
3122  
3123  From F<d_setpwent.U>:
3124  
3125  This variable conditionally defines the C<HAS_SETPWENT> symbol, which
3126  indicates to the C program that the setpwent() routine is available
3127  for initializing sequential access to the passwd database.
3128  
3129  =item C<d_setpwent_r>
3130  
3131  From F<d_setpwent_r.U>:
3132  
3133  This variable conditionally defines the C<HAS_SETPWENT_R> symbol,
3134  which indicates to the C program that the setpwent_r()
3135  routine is available.
3136  
3137  =item C<d_setregid>
3138  
3139  From F<d_setregid.U>:
3140  
3141  This variable conditionally defines C<HAS_SETREGID> if setregid() is
3142  available to change the real and effective gid of the current
3143  process.
3144  
3145  =item C<d_setresgid>
3146  
3147  From F<d_setregid.U>:
3148  
3149  This variable conditionally defines C<HAS_SETRESGID> if setresgid() is
3150  available to change the real, effective and saved gid of the current
3151  process.
3152  
3153  =item C<d_setresuid>
3154  
3155  From F<d_setreuid.U>:
3156  
3157  This variable conditionally defines C<HAS_SETREUID> if setresuid() is
3158  available to change the real, effective and saved uid of the current
3159  process.
3160  
3161  =item C<d_setreuid>
3162  
3163  From F<d_setreuid.U>:
3164  
3165  This variable conditionally defines C<HAS_SETREUID> if setreuid() is
3166  available to change the real and effective uid of the current
3167  process.
3168  
3169  =item C<d_setrgid>
3170  
3171  From F<d_setrgid.U>:
3172  
3173  This variable conditionally defines the C<HAS_SETRGID> symbol, which
3174  indicates to the C program that the setrgid() routine is available
3175  to change the real gid of the current program.
3176  
3177  =item C<d_setruid>
3178  
3179  From F<d_setruid.U>:
3180  
3181  This variable conditionally defines the C<HAS_SETRUID> symbol, which
3182  indicates to the C program that the setruid() routine is available
3183  to change the real uid of the current program.
3184  
3185  =item C<d_setsent>
3186  
3187  From F<d_setsent.U>:
3188  
3189  This variable conditionally defines C<HAS_SETSERVENT> if setservent() is
3190  available.
3191  
3192  =item C<d_setservent_r>
3193  
3194  From F<d_setservent_r.U>:
3195  
3196  This variable conditionally defines the C<HAS_SETSERVENT_R> symbol,
3197  which indicates to the C program that the setservent_r()
3198  routine is available.
3199  
3200  =item C<d_setsid>
3201  
3202  From F<d_setsid.U>:
3203  
3204  This variable conditionally defines C<HAS_SETSID> if setsid() is
3205  available to set the process group C<ID>.
3206  
3207  =item C<d_setvbuf>
3208  
3209  From F<d_setvbuf.U>:
3210  
3211  This variable conditionally defines the C<HAS_SETVBUF> symbol, which
3212  indicates to the C program that the setvbuf() routine is available
3213  to change buffering on an open stdio stream.
3214  
3215  =item C<d_sfio>
3216  
3217  From F<d_sfio.U>:
3218  
3219  This variable conditionally defines the C<USE_SFIO> symbol,
3220  and indicates whether sfio is available (and should be used).
3221  
3222  =item C<d_shm>
3223  
3224  From F<d_shm.U>:
3225  
3226  This variable conditionally defines the C<HAS_SHM> symbol, which
3227  indicates that the entire shm*(2) library is present.
3228  
3229  =item C<d_shmat>
3230  
3231  From F<d_shmat.U>:
3232  
3233  This variable conditionally defines the C<HAS_SHMAT> symbol, which
3234  indicates to the C program that the shmat() routine is available.
3235  
3236  =item C<d_shmatprototype>
3237  
3238  From F<d_shmat.U>:
3239  
3240  This variable conditionally defines the C<HAS_SHMAT_PROTOTYPE>
3241  symbol, which indicates that F<sys/shm.h> has a prototype for
3242  shmat.
3243  
3244  =item C<d_shmctl>
3245  
3246  From F<d_shmctl.U>:
3247  
3248  This variable conditionally defines the C<HAS_SHMCTL> symbol, which
3249  indicates to the C program that the shmctl() routine is available.
3250  
3251  =item C<d_shmdt>
3252  
3253  From F<d_shmdt.U>:
3254  
3255  This variable conditionally defines the C<HAS_SHMDT> symbol, which
3256  indicates to the C program that the shmdt() routine is available.
3257  
3258  =item C<d_shmget>
3259  
3260  From F<d_shmget.U>:
3261  
3262  This variable conditionally defines the C<HAS_SHMGET> symbol, which
3263  indicates to the C program that the shmget() routine is available.
3264  
3265  =item C<d_sigaction>
3266  
3267  From F<d_sigaction.U>:
3268  
3269  This variable conditionally defines the C<HAS_SIGACTION> symbol, which
3270  indicates that the Vr4 sigaction() routine is available.
3271  
3272  =item C<d_signbit>
3273  
3274  From F<d_signbit.U>:
3275  
3276  This variable conditionally defines the C<HAS_SIGNBIT> symbol, which
3277  indicates to the C program that the signbit() routine is available
3278  and safe to use with perl's intern C<NV> type.
3279  
3280  =item C<d_sigprocmask>
3281  
3282  From F<d_sigprocmask.U>:
3283  
3284  This variable conditionally defines C<HAS_SIGPROCMASK>
3285  if sigprocmask() is available to examine or change the signal mask
3286  of the calling process.
3287  
3288  =item C<d_sigsetjmp>
3289  
3290  From F<d_sigsetjmp.U>:
3291  
3292  This variable conditionally defines the C<HAS_SIGSETJMP> symbol,
3293  which indicates that the sigsetjmp() routine is available to
3294  call setjmp() and optionally save the process's signal mask.
3295  
3296  =item C<d_sitearch>
3297  
3298  From F<sitearch.U>:
3299  
3300  This variable conditionally defines C<SITEARCH> to hold the pathname
3301  of architecture-dependent library files for $package.  If
3302  $sitearch is the same as $archlib, then this is set to undef.
3303  
3304  =item C<d_snprintf>
3305  
3306  From F<d_snprintf.U>:
3307  
3308  This variable conditionally defines the C<HAS_SNPRINTF> symbol, which
3309  indicates to the C program that the snprintf () library function
3310  is available.
3311  
3312  =item C<d_sockatmark>
3313  
3314  From F<d_sockatmark.U>:
3315  
3316  This variable conditionally defines the C<HAS_SOCKATMARK> symbol, which
3317  indicates to the C program that the sockatmark() routine is available.
3318  
3319  =item C<d_sockatmarkproto>
3320  
3321  From F<d_sockatmarkproto.U>:
3322  
3323  This variable conditionally defines the C<HAS_SOCKATMARK_PROTO> symbol,
3324  which indicates to the C program that the system provides
3325  a prototype for the sockatmark() function.  Otherwise, it is
3326  up to the program to supply one.
3327  
3328  =item C<d_socket>
3329  
3330  From F<d_socket.U>:
3331  
3332  This variable conditionally defines C<HAS_SOCKET>, which indicates
3333  that the C<BSD> socket interface is supported.
3334  
3335  =item C<d_socklen_t>
3336  
3337  From F<d_socklen_t.U>:
3338  
3339  This symbol will be defined if the C compiler supports socklen_t.
3340  
3341  =item C<d_sockpair>
3342  
3343  From F<d_socket.U>:
3344  
3345  This variable conditionally defines the C<HAS_SOCKETPAIR> symbol, which
3346  indicates that the C<BSD> socketpair() is supported.
3347  
3348  =item C<d_socks5_init>
3349  
3350  From F<d_socks5_init.U>:
3351  
3352  This variable conditionally defines the HAS_SOCKS5_INIT symbol, which
3353  indicates to the C program that the socks5_init() routine is available.
3354  
3355  =item C<d_sprintf_returns_strlen>
3356  
3357  From F<d_sprintf_len.U>:
3358  
3359  This variable defines whether sprintf returns the length of the string
3360  (as per the C<ANSI> spec). Some C libraries retain compatibility with
3361  pre-C<ANSI> C and return a pointer to the passed in buffer; for these
3362  this variable will be undef.
3363  
3364  =item C<d_sqrtl>
3365  
3366  From F<d_sqrtl.U>:
3367  
3368  This variable conditionally defines the C<HAS_SQRTL> symbol, which
3369  indicates to the C program that the sqrtl() routine is available.
3370  
3371  =item C<d_srand48_r>
3372  
3373  From F<d_srand48_r.U>:
3374  
3375  This variable conditionally defines the HAS_SRAND48_R symbol,
3376  which indicates to the C program that the srand48_r()
3377  routine is available.
3378  
3379  =item C<d_srandom_r>
3380  
3381  From F<d_srandom_r.U>:
3382  
3383  This variable conditionally defines the C<HAS_SRANDOM_R> symbol,
3384  which indicates to the C program that the srandom_r()
3385  routine is available.
3386  
3387  =item C<d_sresgproto>
3388  
3389  From F<d_sresgproto.U>:
3390  
3391  This variable conditionally defines the C<HAS_SETRESGID_PROTO> symbol,
3392  which indicates to the C program that the system provides
3393  a prototype for the setresgid() function.  Otherwise, it is
3394  up to the program to supply one.
3395  
3396  =item C<d_sresuproto>
3397  
3398  From F<d_sresuproto.U>:
3399  
3400  This variable conditionally defines the C<HAS_SETRESUID_PROTO> symbol,
3401  which indicates to the C program that the system provides
3402  a prototype for the setresuid() function.  Otherwise, it is
3403  up to the program to supply one.
3404  
3405  =item C<d_statblks>
3406  
3407  From F<d_statblks.U>:
3408  
3409  This variable conditionally defines C<USE_STAT_BLOCKS>
3410  if this system has a stat structure declaring
3411  st_blksize and st_blocks.
3412  
3413  =item C<d_statfs_f_flags>
3414  
3415  From F<d_statfs_f_flags.U>:
3416  
3417  This variable conditionally defines the C<HAS_STRUCT_STATFS_F_FLAGS>
3418  symbol, which indicates to struct statfs from has f_flags member.
3419  This kind of struct statfs is coming from F<sys/mount.h> (C<BSD>),
3420  not from F<sys/statfs.h> (C<SYSV>).
3421  
3422  =item C<d_statfs_s>
3423  
3424  From F<d_statfs_s.U>:
3425  
3426  This variable conditionally defines the C<HAS_STRUCT_STATFS> symbol,
3427  which indicates that the struct statfs is supported.
3428  
3429  =item C<d_statvfs>
3430  
3431  From F<d_statvfs.U>:
3432  
3433  This variable conditionally defines the C<HAS_STATVFS> symbol, which
3434  indicates to the C program that the statvfs() routine is available.
3435  
3436  =item C<d_stdio_cnt_lval>
3437  
3438  From F<d_stdstdio.U>:
3439  
3440  This variable conditionally defines C<STDIO_CNT_LVALUE> if the
3441  C<FILE_cnt> macro can be used as an lvalue.
3442  
3443  =item C<d_stdio_ptr_lval>
3444  
3445  From F<d_stdstdio.U>:
3446  
3447  This variable conditionally defines C<STDIO_PTR_LVALUE> if the
3448  C<FILE_ptr> macro can be used as an lvalue.
3449  
3450  =item C<d_stdio_ptr_lval_nochange_cnt>
3451  
3452  From F<d_stdstdio.U>:
3453  
3454  This symbol is defined if using the C<FILE_ptr> macro as an lvalue
3455  to increase the pointer by n leaves File_cnt(fp) unchanged.
3456  
3457  =item C<d_stdio_ptr_lval_sets_cnt>
3458  
3459  From F<d_stdstdio.U>:
3460  
3461  This symbol is defined if using the C<FILE_ptr> macro as an lvalue
3462  to increase the pointer by n has the side effect of decreasing the
3463  value of File_cnt(fp) by n.
3464  
3465  =item C<d_stdio_stream_array>
3466  
3467  From F<stdio_streams.U>:
3468  
3469  This variable tells whether there is an array holding
3470  the stdio streams.
3471  
3472  =item C<d_stdiobase>
3473  
3474  From F<d_stdstdio.U>:
3475  
3476  This variable conditionally defines C<USE_STDIO_BASE> if this system
3477  has a C<FILE> structure declaring a usable _base field (or equivalent)
3478  in F<stdio.h>.
3479  
3480  =item C<d_stdstdio>
3481  
3482  From F<d_stdstdio.U>:
3483  
3484  This variable conditionally defines C<USE_STDIO_PTR> if this system
3485  has a C<FILE> structure declaring usable _ptr and _cnt fields (or
3486  equivalent) in F<stdio.h>.
3487  
3488  =item C<d_strchr>
3489  
3490  From F<d_strchr.U>:
3491  
3492  This variable conditionally defines C<HAS_STRCHR> if strchr() and
3493  strrchr() are available for string searching.
3494  
3495  =item C<d_strcoll>
3496  
3497  From F<d_strcoll.U>:
3498  
3499  This variable conditionally defines C<HAS_STRCOLL> if strcoll() is
3500  available to compare strings using collating information.
3501  
3502  =item C<d_strctcpy>
3503  
3504  From F<d_strctcpy.U>:
3505  
3506  This variable conditionally defines the C<USE_STRUCT_COPY> symbol, which
3507  indicates to the C program that this C compiler knows how to copy
3508  structures.
3509  
3510  =item C<d_strerrm>
3511  
3512  From F<d_strerror.U>:
3513  
3514  This variable holds what Strerrr is defined as to translate an error
3515  code condition into an error message string. It could be C<strerror>
3516  or a more C<complex> macro emulating strrror with sys_errlist[], or the
3517  C<unknown> string when both strerror and sys_errlist are missing.
3518  
3519  =item C<d_strerror>
3520  
3521  From F<d_strerror.U>:
3522  
3523  This variable conditionally defines C<HAS_STRERROR> if strerror() is
3524  available to translate error numbers to strings.
3525  
3526  =item C<d_strerror_r>
3527  
3528  From F<d_strerror_r.U>:
3529  
3530  This variable conditionally defines the C<HAS_STRERROR_R> symbol,
3531  which indicates to the C program that the strerror_r()
3532  routine is available.
3533  
3534  =item C<d_strftime>
3535  
3536  From F<d_strftime.U>:
3537  
3538  This variable conditionally defines the C<HAS_STRFTIME> symbol, which
3539  indicates to the C program that the strftime() routine is available.
3540  
3541  =item C<d_strlcat>
3542  
3543  From F<d_strlcat.U>:
3544  
3545  This variable conditionally defines the C<HAS_STRLCAT> symbol, which
3546  indicates to the C program that the strlcat () routine is available.
3547  
3548  =item C<d_strlcpy>
3549  
3550  From F<d_strlcpy.U>:
3551  
3552  This variable conditionally defines the C<HAS_STRLCPY> symbol, which
3553  indicates to the C program that the strlcpy () routine is available.
3554  
3555  =item C<d_strtod>
3556  
3557  From F<d_strtod.U>:
3558  
3559  This variable conditionally defines the C<HAS_STRTOD> symbol, which
3560  indicates to the C program that the strtod() routine is available
3561  to provide better numeric string conversion than atof().
3562  
3563  =item C<d_strtol>
3564  
3565  From F<d_strtol.U>:
3566  
3567  This variable conditionally defines the C<HAS_STRTOL> symbol, which
3568  indicates to the C program that the strtol() routine is available
3569  to provide better numeric string conversion than atoi() and friends.
3570  
3571  =item C<d_strtold>
3572  
3573  From F<d_strtold.U>:
3574  
3575  This variable conditionally defines the C<HAS_STRTOLD> symbol, which
3576  indicates to the C program that the strtold() routine is available.
3577  
3578  =item C<d_strtoll>
3579  
3580  From F<d_strtoll.U>:
3581  
3582  This variable conditionally defines the C<HAS_STRTOLL> symbol, which
3583  indicates to the C program that the strtoll() routine is available.
3584  
3585  =item C<d_strtoq>
3586  
3587  From F<d_strtoq.U>:
3588  
3589  This variable conditionally defines the C<HAS_STRTOQ> symbol, which
3590  indicates to the C program that the strtoq() routine is available.
3591  
3592  =item C<d_strtoul>
3593  
3594  From F<d_strtoul.U>:
3595  
3596  This variable conditionally defines the C<HAS_STRTOUL> symbol, which
3597  indicates to the C program that the strtoul() routine is available
3598  to provide conversion of strings to unsigned long.
3599  
3600  =item C<d_strtoull>
3601  
3602  From F<d_strtoull.U>:
3603  
3604  This variable conditionally defines the C<HAS_STRTOULL> symbol, which
3605  indicates to the C program that the strtoull() routine is available.
3606  
3607  =item C<d_strtouq>
3608  
3609  From F<d_strtouq.U>:
3610  
3611  This variable conditionally defines the C<HAS_STRTOUQ> symbol, which
3612  indicates to the C program that the strtouq() routine is available.
3613  
3614  =item C<d_strxfrm>
3615  
3616  From F<d_strxfrm.U>:
3617  
3618  This variable conditionally defines C<HAS_STRXFRM> if strxfrm() is
3619  available to transform strings.
3620  
3621  =item C<d_suidsafe>
3622  
3623  From F<d_dosuid.U>:
3624  
3625  This variable conditionally defines C<SETUID_SCRIPTS_ARE_SECURE_NOW>
3626  if setuid scripts can be secure.  This test looks in F</dev/fd/>.
3627  
3628  =item C<d_symlink>
3629  
3630  From F<d_symlink.U>:
3631  
3632  This variable conditionally defines the C<HAS_SYMLINK> symbol, which
3633  indicates to the C program that the symlink() routine is available
3634  to create symbolic links.
3635  
3636  =item C<d_syscall>
3637  
3638  From F<d_syscall.U>:
3639  
3640  This variable conditionally defines C<HAS_SYSCALL> if syscall() is
3641  available call arbitrary system calls.
3642  
3643  =item C<d_syscallproto>
3644  
3645  From F<d_syscallproto.U>:
3646  
3647  This variable conditionally defines the C<HAS_SYSCALL_PROTO> symbol,
3648  which indicates to the C program that the system provides
3649  a prototype for the syscall() function.  Otherwise, it is
3650  up to the program to supply one.
3651  
3652  =item C<d_sysconf>
3653  
3654  From F<d_sysconf.U>:
3655  
3656  This variable conditionally defines the C<HAS_SYSCONF> symbol, which
3657  indicates to the C program that the sysconf() routine is available
3658  to determine system related limits and options.
3659  
3660  =item C<d_sysernlst>
3661  
3662  From F<d_strerror.U>:
3663  
3664  This variable conditionally defines C<HAS_SYS_ERRNOLIST> if sys_errnolist[]
3665  is available to translate error numbers to the symbolic name.
3666  
3667  =item C<d_syserrlst>
3668  
3669  From F<d_strerror.U>:
3670  
3671  This variable conditionally defines C<HAS_SYS_ERRLIST> if sys_errlist[] is
3672  available to translate error numbers to strings.
3673  
3674  =item C<d_system>
3675  
3676  From F<d_system.U>:
3677  
3678  This variable conditionally defines C<HAS_SYSTEM> if system() is
3679  available to issue a shell command.
3680  
3681  =item C<d_tcgetpgrp>
3682  
3683  From F<d_tcgtpgrp.U>:
3684  
3685  This variable conditionally defines the C<HAS_TCGETPGRP> symbol, which
3686  indicates to the C program that the tcgetpgrp() routine is available.
3687  to get foreground process group C<ID>.
3688  
3689  =item C<d_tcsetpgrp>
3690  
3691  From F<d_tcstpgrp.U>:
3692  
3693  This variable conditionally defines the C<HAS_TCSETPGRP> symbol, which
3694  indicates to the C program that the tcsetpgrp() routine is available
3695  to set foreground process group C<ID>.
3696  
3697  =item C<d_telldir>
3698  
3699  From F<d_readdir.U>:
3700  
3701  This variable conditionally defines C<HAS_TELLDIR> if telldir() is
3702  available.
3703  
3704  =item C<d_telldirproto>
3705  
3706  From F<d_telldirproto.U>:
3707  
3708  This variable conditionally defines the C<HAS_TELLDIR_PROTO> symbol,
3709  which indicates to the C program that the system provides
3710  a prototype for the telldir() function.  Otherwise, it is
3711  up to the program to supply one.
3712  
3713  =item C<d_time>
3714  
3715  From F<d_time.U>:
3716  
3717  This variable conditionally defines the C<HAS_TIME> symbol, which indicates
3718  that the time() routine exists.  The time() routine is normaly
3719  provided on C<UNIX> systems.
3720  
3721  =item C<d_times>
3722  
3723  From F<d_times.U>:
3724  
3725  This variable conditionally defines the C<HAS_TIMES> symbol, which indicates
3726  that the times() routine exists.  The times() routine is normaly
3727  provided on C<UNIX> systems. You may have to include <sys/times.h>.
3728  
3729  =item C<d_tm_tm_gmtoff>
3730  
3731  From F<i_time.U>:
3732  
3733  This variable conditionally defines C<HAS_TM_TM_GMTOFF>, which indicates
3734  indicates to the C program that the struct tm has the tm_gmtoff field.
3735  
3736  =item C<d_tm_tm_zone>
3737  
3738  From F<i_time.U>:
3739  
3740  This variable conditionally defines C<HAS_TM_TM_ZONE>, which indicates
3741  indicates to the C program that the struct tm has the tm_zone field.
3742  
3743  =item C<d_tmpnam_r>
3744  
3745  From F<d_tmpnam_r.U>:
3746  
3747  This variable conditionally defines the C<HAS_TMPNAM_R> symbol,
3748  which indicates to the C program that the tmpnam_r()
3749  routine is available.
3750  
3751  =item C<d_truncate>
3752  
3753  From F<d_truncate.U>:
3754  
3755  This variable conditionally defines C<HAS_TRUNCATE> if truncate() is
3756  available to truncate files.
3757  
3758  =item C<d_ttyname_r>
3759  
3760  From F<d_ttyname_r.U>:
3761  
3762  This variable conditionally defines the C<HAS_TTYNAME_R> symbol,
3763  which indicates to the C program that the ttyname_r()
3764  routine is available.
3765  
3766  =item C<d_tzname>
3767  
3768  From F<d_tzname.U>:
3769  
3770  This variable conditionally defines C<HAS_TZNAME> if tzname[] is
3771  available to access timezone names.
3772  
3773  =item C<d_u32align>
3774  
3775  From F<d_u32align.U>:
3776  
3777  This variable tells whether you must access character data
3778  through U32-aligned pointers.
3779  
3780  =item C<d_ualarm>
3781  
3782  From F<d_ualarm.U>:
3783  
3784  This variable conditionally defines the C<HAS_UALARM> symbol, which
3785  indicates to the C program that the ualarm() routine is available.
3786  
3787  =item C<d_umask>
3788  
3789  From F<d_umask.U>:
3790  
3791  This variable conditionally defines the C<HAS_UMASK> symbol, which
3792  indicates to the C program that the umask() routine is available.
3793  to set and get the value of the file creation mask.
3794  
3795  =item C<d_uname>
3796  
3797  From F<d_gethname.U>:
3798  
3799  This variable conditionally defines the C<HAS_UNAME> symbol, which
3800  indicates to the C program that the uname() routine may be
3801  used to derive the host name.
3802  
3803  =item C<d_union_semun>
3804  
3805  From F<d_union_semun.U>:
3806  
3807  This variable conditionally defines C<HAS_UNION_SEMUN> if the
3808  union semun is defined by including <sys/sem.h>.
3809  
3810  =item C<d_unordered>
3811  
3812  From F<d_unordered.U>:
3813  
3814  This variable conditionally defines the C<HAS_UNORDERED> symbol, which
3815  indicates to the C program that the unordered() routine is available.
3816  
3817  =item C<d_unsetenv>
3818  
3819  From F<d_unsetenv.U>:
3820  
3821  This variable conditionally defines the C<HAS_UNSETENV> symbol, which
3822  indicates to the C program that the unsetenv () routine is available.
3823  
3824  =item C<d_usleep>
3825  
3826  From F<d_usleep.U>:
3827  
3828  This variable conditionally defines C<HAS_USLEEP> if usleep() is
3829  available to do high granularity sleeps.
3830  
3831  =item C<d_usleepproto>
3832  
3833  From F<d_usleepproto.U>:
3834  
3835  This variable conditionally defines the C<HAS_USLEEP_PROTO> symbol,
3836  which indicates to the C program that the system provides
3837  a prototype for the usleep() function.  Otherwise, it is
3838  up to the program to supply one.
3839  
3840  =item C<d_ustat>
3841  
3842  From F<d_ustat.U>:
3843  
3844  This variable conditionally defines C<HAS_USTAT> if ustat() is
3845  available to query file system statistics by dev_t.
3846  
3847  =item C<d_vendorarch>
3848  
3849  From F<vendorarch.U>:
3850  
3851  This variable conditionally defined C<PERL_VENDORARCH>.
3852  
3853  =item C<d_vendorbin>
3854  
3855  From F<vendorbin.U>:
3856  
3857  This variable conditionally defines C<PERL_VENDORBIN>.
3858  
3859  =item C<d_vendorlib>
3860  
3861  From F<vendorlib.U>:
3862  
3863  This variable conditionally defines C<PERL_VENDORLIB>.
3864  
3865  =item C<d_vendorscript>
3866  
3867  From F<vendorscript.U>:
3868  
3869  This variable conditionally defines C<PERL_VENDORSCRIPT>.
3870  
3871  =item C<d_vfork>
3872  
3873  From F<d_vfork.U>:
3874  
3875  This variable conditionally defines the C<HAS_VFORK> symbol, which
3876  indicates the vfork() routine is available.
3877  
3878  =item C<d_void_closedir>
3879  
3880  From F<d_closedir.U>:
3881  
3882  This variable conditionally defines C<VOID_CLOSEDIR> if closedir()
3883  does not return a value.
3884  
3885  =item C<d_voidsig>
3886  
3887  From F<d_voidsig.U>:
3888  
3889  This variable conditionally defines C<VOIDSIG> if this system
3890  declares "void (*signal(...))()" in F<signal.h>.  The old way was to
3891  declare it as "int (*signal(...))()".
3892  
3893  =item C<d_voidtty>
3894  
3895  From F<i_sysioctl.U>:
3896  
3897  This variable conditionally defines C<USE_IOCNOTTY> to indicate that the
3898  ioctl() call with C<TIOCNOTTY> should be used to void tty association.
3899  Otherwise (on C<USG> probably), it is enough to close the standard file
3900  decriptors and do a setpgrp().
3901  
3902  =item C<d_volatile>
3903  
3904  From F<d_volatile.U>:
3905  
3906  This variable conditionally defines the C<HASVOLATILE> symbol, which
3907  indicates to the C program that this C compiler knows about the
3908  volatile declaration.
3909  
3910  =item C<d_vprintf>
3911  
3912  From F<d_vprintf.U>:
3913  
3914  This variable conditionally defines the C<HAS_VPRINTF> symbol, which
3915  indicates to the C program that the vprintf() routine is available
3916  to printf with a pointer to an argument list.
3917  
3918  =item C<d_vsnprintf>
3919  
3920  From F<d_snprintf.U>:
3921  
3922  This variable conditionally defines the C<HAS_VSNPRINTF> symbol, which
3923  indicates to the C program that the vsnprintf () library function
3924  is available.
3925  
3926  =item C<d_wait4>
3927  
3928  From F<d_wait4.U>:
3929  
3930  This variable conditionally defines the HAS_WAIT4 symbol, which
3931  indicates the wait4() routine is available.
3932  
3933  =item C<d_waitpid>
3934  
3935  From F<d_waitpid.U>:
3936  
3937  This variable conditionally defines C<HAS_WAITPID> if waitpid() is
3938  available to wait for child process.
3939  
3940  =item C<d_wcstombs>
3941  
3942  From F<d_wcstombs.U>:
3943  
3944  This variable conditionally defines the C<HAS_WCSTOMBS> symbol, which
3945  indicates to the C program that the wcstombs() routine is available
3946  to convert wide character strings to multibyte strings.
3947  
3948  =item C<d_wctomb>
3949  
3950  From F<d_wctomb.U>:
3951  
3952  This variable conditionally defines the C<HAS_WCTOMB> symbol, which
3953  indicates to the C program that the wctomb() routine is available
3954  to convert a wide character to a multibyte.
3955  
3956  =item C<d_writev>
3957  
3958  From F<d_writev.U>:
3959  
3960  This variable conditionally defines the C<HAS_WRITEV> symbol, which
3961  indicates to the C program that the writev() routine is available.
3962  
3963  =item C<d_xenix>
3964  
3965  From F<Guess.U>:
3966  
3967  This variable conditionally defines the symbol C<XENIX>, which alerts
3968  the C program that it runs under Xenix.
3969  
3970  =item C<date>
3971  
3972  From F<Loc.U>:
3973  
3974  This variable is used internally by Configure to determine the
3975  full pathname (if any) of the date program.  After Configure runs,
3976  the value is reset to a plain C<date> and is not useful.
3977  
3978  =item C<db_hashtype>
3979  
3980  From F<i_db.U>:
3981  
3982  This variable contains the type of the hash structure element
3983  in the <db.h> header file.  In older versions of C<DB>, it was
3984  int, while in newer ones it is u_int32_t.
3985  
3986  =item C<db_prefixtype>
3987  
3988  From F<i_db.U>:
3989  
3990  This variable contains the type of the prefix structure element
3991  in the <db.h> header file.  In older versions of C<DB>, it was
3992  int, while in newer ones it is size_t.
3993  
3994  =item C<db_version_major>
3995  
3996  From F<i_db.U>:
3997  
3998  This variable contains the major version number of
3999  Berkeley C<DB> found in the <db.h> header file.
4000  
4001  =item C<db_version_minor>
4002  
4003  From F<i_db.U>:
4004  
4005  This variable contains the minor version number of
4006  Berkeley C<DB> found in the <db.h> header file.
4007  For C<DB> version 1 this is always 0.
4008  
4009  =item C<db_version_patch>
4010  
4011  From F<i_db.U>:
4012  
4013  This variable contains the patch version number of
4014  Berkeley C<DB> found in the <db.h> header file.
4015  For C<DB> version 1 this is always 0.
4016  
4017  =item C<defvoidused>
4018  
4019  From F<voidflags.U>:
4020  
4021  This variable contains the default value of the C<VOIDUSED> symbol (15).
4022  
4023  =item C<direntrytype>
4024  
4025  From F<i_dirent.U>:
4026  
4027  This symbol is set to C<struct direct> or C<struct dirent> depending on
4028  whether dirent is available or not. You should use this pseudo type to
4029  portably declare your directory entries.
4030  
4031  =item C<dlext>
4032  
4033  From F<dlext.U>:
4034  
4035  This variable contains the extension that is to be used for the
4036  dynamically loaded modules that perl generaties.
4037  
4038  =item C<dlsrc>
4039  
4040  From F<dlsrc.U>:
4041  
4042  This variable contains the name of the dynamic loading file that
4043  will be used with the package.
4044  
4045  =item C<doublesize>
4046  
4047  From F<doublesize.U>:
4048  
4049  This variable contains the value of the C<DOUBLESIZE> symbol, which
4050  indicates to the C program how many bytes there are in a double.
4051  
4052  =item C<drand01>
4053  
4054  From F<randfunc.U>:
4055  
4056  Indicates the macro to be used to generate normalized
4057  random numbers.  Uses randfunc, often divided by
4058  (double) (((unsigned long) 1 << randbits)) in order to
4059  normalize the result.
4060  In C programs, the macro C<Drand01> is mapped to drand01.
4061  
4062  =item C<drand48_r_proto>
4063  
4064  From F<d_drand48_r.U>:
4065  
4066  This variable encodes the prototype of drand48_r.
4067  It is zero if d_drand48_r is undef, and one of the
4068  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_drand48_r
4069  is defined.
4070  
4071  =item C<dynamic_ext>
4072  
4073  From F<Extensions.U>:
4074  
4075  This variable holds a list of C<XS> extension files we want to
4076  link dynamically into the package.  It is used by Makefile.
4077  
4078  =back
4079  
4080  =head2 e
4081  
4082  =over 4
4083  
4084  =item C<eagain>
4085  
4086  From F<nblock_io.U>:
4087  
4088  This variable bears the symbolic errno code set by read() when no
4089  data is present on the file and non-blocking I/O was enabled (otherwise,
4090  read() blocks naturally).
4091  
4092  =item C<ebcdic>
4093  
4094  From F<ebcdic.U>:
4095  
4096  This variable conditionally defines C<EBCDIC> if this
4097  system uses C<EBCDIC> encoding.  Among other things, this
4098  means that the character ranges are not contiguous.
4099  See F<trnl.U>
4100  
4101  =item C<echo>
4102  
4103  From F<Loc.U>:
4104  
4105  This variable is used internally by Configure to determine the
4106  full pathname (if any) of the echo program.  After Configure runs,
4107  the value is reset to a plain C<echo> and is not useful.
4108  
4109  =item C<egrep>
4110  
4111  From F<Loc.U>:
4112  
4113  This variable is used internally by Configure to determine the
4114  full pathname (if any) of the egrep program.  After Configure runs,
4115  the value is reset to a plain C<egrep> and is not useful.
4116  
4117  =item C<emacs>
4118  
4119  From F<Loc.U>:
4120  
4121  This variable is defined but not used by Configure.
4122  The value is a plain '' and is not useful.
4123  
4124  =item C<endgrent_r_proto>
4125  
4126  From F<d_endgrent_r.U>:
4127  
4128  This variable encodes the prototype of endgrent_r.
4129  It is zero if d_endgrent_r is undef, and one of the
4130  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_endgrent_r
4131  is defined.
4132  
4133  =item C<endhostent_r_proto>
4134  
4135  From F<d_endhostent_r.U>:
4136  
4137  This variable encodes the prototype of endhostent_r.
4138  It is zero if d_endhostent_r is undef, and one of the
4139  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_endhostent_r
4140  is defined.
4141  
4142  =item C<endnetent_r_proto>
4143  
4144  From F<d_endnetent_r.U>:
4145  
4146  This variable encodes the prototype of endnetent_r.
4147  It is zero if d_endnetent_r is undef, and one of the
4148  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_endnetent_r
4149  is defined.
4150  
4151  =item C<endprotoent_r_proto>
4152  
4153  From F<d_endprotoent_r.U>:
4154  
4155  This variable encodes the prototype of endprotoent_r.
4156  It is zero if d_endprotoent_r is undef, and one of the
4157  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_endprotoent_r
4158  is defined.
4159  
4160  =item C<endpwent_r_proto>
4161  
4162  From F<d_endpwent_r.U>:
4163  
4164  This variable encodes the prototype of endpwent_r.
4165  It is zero if d_endpwent_r is undef, and one of the
4166  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_endpwent_r
4167  is defined.
4168  
4169  =item C<endservent_r_proto>
4170  
4171  From F<d_endservent_r.U>:
4172  
4173  This variable encodes the prototype of endservent_r.
4174  It is zero if d_endservent_r is undef, and one of the
4175  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_endservent_r
4176  is defined.
4177  
4178  =item C<eunicefix>
4179  
4180  From F<Init.U>:
4181  
4182  When running under Eunice this variable contains a command which will
4183  convert a shell script to the proper form of text file for it to be
4184  executable by the shell.  On other systems it is a no-op.
4185  
4186  =item C<exe_ext>
4187  
4188  From F<Unix.U>:
4189  
4190  This is an old synonym for _exe.
4191  
4192  =item C<expr>
4193  
4194  From F<Loc.U>:
4195  
4196  This variable is used internally by Configure to determine the
4197  full pathname (if any) of the expr program.  After Configure runs,
4198  the value is reset to a plain C<expr> and is not useful.
4199  
4200  =item C<extensions>
4201  
4202  From F<Extensions.U>:
4203  
4204  This variable holds a list of all extension files (both C<XS> and
4205  non-xs linked into the package.  It is propagated to F<Config.pm>
4206  and is typically used to test whether a particular extesion
4207  is available.
4208  
4209  =item C<extras>
4210  
4211  From F<Extras.U>:
4212  
4213  This variable holds a list of extra modules to install.
4214  
4215  =back
4216  
4217  =head2 f
4218  
4219  =over 4
4220  
4221  =item C<fflushall>
4222  
4223  From F<fflushall.U>:
4224  
4225  This symbol, if defined, tells that to flush
4226  all pending stdio output one must loop through all
4227  the stdio file handles stored in an array and fflush them.
4228  Note that if fflushNULL is defined, fflushall will not
4229  even be probed for and will be left undefined.
4230  
4231  =item C<fflushNULL>
4232  
4233  From F<fflushall.U>:
4234  
4235  This symbol, if defined, tells that fflush(C<NULL>) does flush
4236  all pending stdio output.
4237  
4238  =item C<find>
4239  
4240  From F<Loc.U>:
4241  
4242  This variable is defined but not used by Configure.
4243  The value is a plain '' and is not useful.
4244  
4245  =item C<firstmakefile>
4246  
4247  From F<Unix.U>:
4248  
4249  This variable defines the first file searched by make.  On unix,
4250  it is makefile (then Makefile).  On case-insensitive systems,
4251  it might be something else.  This is only used to deal with
4252  convoluted make depend tricks.
4253  
4254  =item C<flex>
4255  
4256  From F<Loc.U>:
4257  
4258  This variable is defined but not used by Configure.
4259  The value is a plain '' and is not useful.
4260  
4261  =item C<fpossize>
4262  
4263  From F<fpossize.U>:
4264  
4265  This variable contains the size of a fpostype in bytes.
4266  
4267  =item C<fpostype>
4268  
4269  From F<fpostype.U>:
4270  
4271  This variable defines Fpos_t to be something like fpos_t, long,
4272  uint, or whatever type is used to declare file positions in libc.
4273  
4274  =item C<freetype>
4275  
4276  From F<mallocsrc.U>:
4277  
4278  This variable contains the return type of free().  It is usually
4279  void, but occasionally int.
4280  
4281  =item C<from>
4282  
4283  From F<Cross.U>:
4284  
4285  This variable contains the command used by Configure
4286  to copy files from the target host.  Useful and available
4287  only during Perl build.
4288  The string C<:> if not cross-compiling.
4289  
4290  =item C<full_ar>
4291  
4292  From F<Loc_ar.U>:
4293  
4294  This variable contains the full pathname to C<ar>, whether or
4295  not the user has specified C<portability>.  This is only used
4296  in the F<Makefile.SH>.
4297  
4298  =item C<full_csh>
4299  
4300  From F<d_csh.U>:
4301  
4302  This variable contains the full pathname to C<csh>, whether or
4303  not the user has specified C<portability>.  This is only used
4304  in the compiled C program, and we assume that all systems which
4305  can share this executable will have the same full pathname to
4306  F<csh.>
4307  
4308  =item C<full_sed>
4309  
4310  From F<Loc_sed.U>:
4311  
4312  This variable contains the full pathname to C<sed>, whether or
4313  not the user has specified C<portability>.  This is only used
4314  in the compiled C program, and we assume that all systems which
4315  can share this executable will have the same full pathname to
4316  F<sed.>
4317  
4318  =back
4319  
4320  =head2 g
4321  
4322  =over 4
4323  
4324  =item C<gccansipedantic>
4325  
4326  From F<gccvers.U>:
4327  
4328  If C<GNU> cc (gcc) is used, this variable will enable (if set) the
4329  -ansi and -pedantic ccflags for building core files (through
4330  cflags script). (See F<Porting/pumpkin.pod> for full description).
4331  
4332  =item C<gccosandvers>
4333  
4334  From F<gccvers.U>:
4335  
4336  If C<GNU> cc (gcc) is used, this variable holds the operating system
4337  and version used to compile gcc.  It is set to '' if not gcc,
4338  or if nothing useful can be parsed as the os version.
4339  
4340  =item C<gccversion>
4341  
4342  From F<gccvers.U>:
4343  
4344  If C<GNU> cc (gcc) is used, this variable holds C<1> or C<2> to
4345  indicate whether the compiler is version 1 or 2.  This is used in
4346  setting some of the default cflags.  It is set to '' if not gcc.
4347  
4348  =item C<getgrent_r_proto>
4349  
4350  From F<d_getgrent_r.U>:
4351  
4352  This variable encodes the prototype of getgrent_r.
4353  It is zero if d_getgrent_r is undef, and one of the
4354  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_getgrent_r
4355  is defined.
4356  
4357  =item C<getgrgid_r_proto>
4358  
4359  From F<d_getgrgid_r.U>:
4360  
4361  This variable encodes the prototype of getgrgid_r.
4362  It is zero if d_getgrgid_r is undef, and one of the
4363  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_getgrgid_r
4364  is defined.
4365  
4366  =item C<getgrnam_r_proto>
4367  
4368  From F<d_getgrnam_r.U>:
4369  
4370  This variable encodes the prototype of getgrnam_r.
4371  It is zero if d_getgrnam_r is undef, and one of the
4372  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_getgrnam_r
4373  is defined.
4374  
4375  =item C<gethostbyaddr_r_proto>
4376  
4377  From F<d_gethostbyaddr_r.U>:
4378  
4379  This variable encodes the prototype of gethostbyaddr_r.
4380  It is zero if d_gethostbyaddr_r is undef, and one of the
4381  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_gethostbyaddr_r
4382  is defined.
4383  
4384  =item C<gethostbyname_r_proto>
4385  
4386  From F<d_gethostbyname_r.U>:
4387  
4388  This variable encodes the prototype of gethostbyname_r.
4389  It is zero if d_gethostbyname_r is undef, and one of the
4390  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_gethostbyname_r
4391  is defined.
4392  
4393  =item C<gethostent_r_proto>
4394  
4395  From F<d_gethostent_r.U>:
4396  
4397  This variable encodes the prototype of gethostent_r.
4398  It is zero if d_gethostent_r is undef, and one of the
4399  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_gethostent_r
4400  is defined.
4401  
4402  =item C<getlogin_r_proto>
4403  
4404  From F<d_getlogin_r.U>:
4405  
4406  This variable encodes the prototype of getlogin_r.
4407  It is zero if d_getlogin_r is undef, and one of the
4408  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_getlogin_r
4409  is defined.
4410  
4411  =item C<getnetbyaddr_r_proto>
4412  
4413  From F<d_getnetbyaddr_r.U>:
4414  
4415  This variable encodes the prototype of getnetbyaddr_r.
4416  It is zero if d_getnetbyaddr_r is undef, and one of the
4417  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_getnetbyaddr_r
4418  is defined.
4419  
4420  =item C<getnetbyname_r_proto>
4421  
4422  From F<d_getnetbyname_r.U>:
4423  
4424  This variable encodes the prototype of getnetbyname_r.
4425  It is zero if d_getnetbyname_r is undef, and one of the
4426  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_getnetbyname_r
4427  is defined.
4428  
4429  =item C<getnetent_r_proto>
4430  
4431  From F<d_getnetent_r.U>:
4432  
4433  This variable encodes the prototype of getnetent_r.
4434  It is zero if d_getnetent_r is undef, and one of the
4435  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_getnetent_r
4436  is defined.
4437  
4438  =item C<getprotobyname_r_proto>
4439  
4440  From F<d_getprotobyname_r.U>:
4441  
4442  This variable encodes the prototype of getprotobyname_r.
4443  It is zero if d_getprotobyname_r is undef, and one of the
4444  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_getprotobyname_r
4445  is defined.
4446  
4447  =item C<getprotobynumber_r_proto>
4448  
4449  From F<d_getprotobynumber_r.U>:
4450  
4451  This variable encodes the prototype of getprotobynumber_r.
4452  It is zero if d_getprotobynumber_r is undef, and one of the
4453  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_getprotobynumber_r
4454  is defined.
4455  
4456  =item C<getprotoent_r_proto>
4457  
4458  From F<d_getprotoent_r.U>:
4459  
4460  This variable encodes the prototype of getprotoent_r.
4461  It is zero if d_getprotoent_r is undef, and one of the
4462  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_getprotoent_r
4463  is defined.
4464  
4465  =item C<getpwent_r_proto>
4466  
4467  From F<d_getpwent_r.U>:
4468  
4469  This variable encodes the prototype of getpwent_r.
4470  It is zero if d_getpwent_r is undef, and one of the
4471  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_getpwent_r
4472  is defined.
4473  
4474  =item C<getpwnam_r_proto>
4475  
4476  From F<d_getpwnam_r.U>:
4477  
4478  This variable encodes the prototype of getpwnam_r.
4479  It is zero if d_getpwnam_r is undef, and one of the
4480  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_getpwnam_r
4481  is defined.
4482  
4483  =item C<getpwuid_r_proto>
4484  
4485  From F<d_getpwuid_r.U>:
4486  
4487  This variable encodes the prototype of getpwuid_r.
4488  It is zero if d_getpwuid_r is undef, and one of the
4489  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_getpwuid_r
4490  is defined.
4491  
4492  =item C<getservbyname_r_proto>
4493  
4494  From F<d_getservbyname_r.U>:
4495  
4496  This variable encodes the prototype of getservbyname_r.
4497  It is zero if d_getservbyname_r is undef, and one of the
4498  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_getservbyname_r
4499  is defined.
4500  
4501  =item C<getservbyport_r_proto>
4502  
4503  From F<d_getservbyport_r.U>:
4504  
4505  This variable encodes the prototype of getservbyport_r.
4506  It is zero if d_getservbyport_r is undef, and one of the
4507  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_getservbyport_r
4508  is defined.
4509  
4510  =item C<getservent_r_proto>
4511  
4512  From F<d_getservent_r.U>:
4513  
4514  This variable encodes the prototype of getservent_r.
4515  It is zero if d_getservent_r is undef, and one of the
4516  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_getservent_r
4517  is defined.
4518  
4519  =item C<getspnam_r_proto>
4520  
4521  From F<d_getspnam_r.U>:
4522  
4523  This variable encodes the prototype of getspnam_r.
4524  It is zero if d_getspnam_r is undef, and one of the
4525  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_getspnam_r
4526  is defined.
4527  
4528  =item C<gidformat>
4529  
4530  From F<gidf.U>:
4531  
4532  This variable contains the format string used for printing a Gid_t.
4533  
4534  =item C<gidsign>
4535  
4536  From F<gidsign.U>:
4537  
4538  This variable contains the signedness of a gidtype.
4539  1 for unsigned, -1 for signed.
4540  
4541  =item C<gidsize>
4542  
4543  From F<gidsize.U>:
4544  
4545  This variable contains the size of a gidtype in bytes.
4546  
4547  =item C<gidtype>
4548  
4549  From F<gidtype.U>:
4550  
4551  This variable defines Gid_t to be something like gid_t, int,
4552  ushort, or whatever type is used to declare the return type
4553  of getgid().  Typically, it is the type of group ids in the kernel.
4554  
4555  =item C<glibpth>
4556  
4557  From F<libpth.U>:
4558  
4559  This variable holds the general path (space-separated) used to
4560  find libraries.  It may contain directories that do not exist on
4561  this platform, libpth is the cleaned-up version.
4562  
4563  =item C<gmake>
4564  
4565  From F<Loc.U>:
4566  
4567  This variable is used internally by Configure to determine the
4568  full pathname (if any) of the gmake program.  After Configure runs,
4569  the value is reset to a plain C<gmake> and is not useful.
4570  
4571  =item C<gmtime_r_proto>
4572  
4573  From F<d_gmtime_r.U>:
4574  
4575  This variable encodes the prototype of gmtime_r.
4576  It is zero if d_gmtime_r is undef, and one of the
4577  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_gmtime_r
4578  is defined.
4579  
4580  =item C<gnulibc_version>
4581  
4582  From F<d_gnulibc.U>:
4583  
4584  This variable contains the version number of the C<GNU> C library.
4585  It is usually something like F<2.2.5>.  It is a plain '' if this
4586  is not the C<GNU> C library, or if the version is unknown.
4587  
4588  =item C<grep>
4589  
4590  From F<Loc.U>:
4591  
4592  This variable is used internally by Configure to determine the
4593  full pathname (if any) of the grep program.  After Configure runs,
4594  the value is reset to a plain C<grep> and is not useful.
4595  
4596  =item C<groupcat>
4597  
4598  From F<nis.U>:
4599  
4600  This variable contains a command that produces the text of the
4601  F</etc/group> file.  This is normally "cat F</etc/group>", but can be
4602  "ypcat group" when C<NIS> is used.
4603  On some systems, such as os390, there may be no equivalent
4604  command, in which case this variable is unset.
4605  
4606  =item C<groupstype>
4607  
4608  From F<groupstype.U>:
4609  
4610  This variable defines Groups_t to be something like gid_t, int,
4611  ushort, or whatever type is used for the second argument to
4612  getgroups() and setgroups().  Usually, this is the same as
4613  gidtype (gid_t), but sometimes it isn't.
4614  
4615  =item C<gzip>
4616  
4617  From F<Loc.U>:
4618  
4619  This variable is used internally by Configure to determine the
4620  full pathname (if any) of the gzip program.  After Configure runs,
4621  the value is reset to a plain C<gzip> and is not useful.
4622  
4623  =back
4624  
4625  =head2 h
4626  
4627  =over 4
4628  
4629  =item C<h_fcntl>
4630  
4631  From F<h_fcntl.U>:
4632  
4633  This is variable gets set in various places to tell i_fcntl that
4634  <fcntl.h> should be included.
4635  
4636  =item C<h_sysfile>
4637  
4638  From F<h_sysfile.U>:
4639  
4640  This is variable gets set in various places to tell i_sys_file that
4641  <sys/file.h> should be included.
4642  
4643  =item C<hint>
4644  
4645  From F<Oldconfig.U>:
4646  
4647  Gives the type of hints used for previous answers. May be one of
4648  C<default>, C<recommended> or C<previous>.
4649  
4650  =item C<hostcat>
4651  
4652  From F<nis.U>:
4653  
4654  This variable contains a command that produces the text of the
4655  F</etc/hosts> file.  This is normally "cat F</etc/hosts>", but can be
4656  "ypcat hosts" when C<NIS> is used.
4657  On some systems, such as os390, there may be no equivalent
4658  command, in which case this variable is unset.
4659  
4660  =item C<html1dir>
4661  
4662  From F<html1dir.U>:
4663  
4664  This variable contains the name of the directory in which html
4665  source pages are to be put.  This directory is for pages
4666  that describe whole programs, not libraries or modules.  It
4667  is intended to correspond roughly to section 1 of the Unix
4668  manuals.
4669  
4670  =item C<html1direxp>
4671  
4672  From F<html1dir.U>:
4673  
4674  This variable is the same as the html1dir variable, but is filename
4675  expanded at configuration time, for convenient use in makefiles.
4676  
4677  =item C<html3dir>
4678  
4679  From F<html3dir.U>:
4680  
4681  This variable contains the name of the directory in which html
4682  source pages are to be put.  This directory is for pages
4683  that describe libraries or modules.  It is intended to
4684  correspond roughly to section 3 of the Unix manuals.
4685  
4686  =item C<html3direxp>
4687  
4688  From F<html3dir.U>:
4689  
4690  This variable is the same as the html3dir variable, but is filename
4691  expanded at configuration time, for convenient use in makefiles.
4692  
4693  =back
4694  
4695  =head2 i
4696  
4697  =over 4
4698  
4699  =item C<i16size>
4700  
4701  From F<perlxv.U>:
4702  
4703  This variable is the size of an I16 in bytes.
4704  
4705  =item C<i16type>
4706  
4707  From F<perlxv.U>:
4708  
4709  This variable contains the C type used for Perl's I16.
4710  
4711  =item C<i32size>
4712  
4713  From F<perlxv.U>:
4714  
4715  This variable is the size of an I32 in bytes.
4716  
4717  =item C<i32type>
4718  
4719  From F<perlxv.U>:
4720  
4721  This variable contains the C type used for Perl's I32.
4722  
4723  =item C<i64size>
4724  
4725  From F<perlxv.U>:
4726  
4727  This variable is the size of an I64 in bytes.
4728  
4729  =item C<i64type>
4730  
4731  From F<perlxv.U>:
4732  
4733  This variable contains the C type used for Perl's I64.
4734  
4735  =item C<i8size>
4736  
4737  From F<perlxv.U>:
4738  
4739  This variable is the size of an I8 in bytes.
4740  
4741  =item C<i8type>
4742  
4743  From F<perlxv.U>:
4744  
4745  This variable contains the C type used for Perl's I8.
4746  
4747  =item C<i_arpainet>
4748  
4749  From F<i_arpainet.U>:
4750  
4751  This variable conditionally defines the C<I_ARPA_INET> symbol,
4752  and indicates whether a C program should include <arpa/inet.h>.
4753  
4754  =item C<i_bsdioctl>
4755  
4756  From F<i_sysioctl.U>:
4757  
4758  This variable conditionally defines the C<I_SYS_BSDIOCTL> symbol, which
4759  indicates to the C program that <sys/bsdioctl.h> exists and should
4760  be included.
4761  
4762  =item C<i_crypt>
4763  
4764  From F<i_crypt.U>:
4765  
4766  This variable conditionally defines the C<I_CRYPT> symbol, and indicates
4767  whether a C program should include <crypt.h>.
4768  
4769  =item C<i_db>
4770  
4771  From F<i_db.U>:
4772  
4773  This variable conditionally defines the C<I_DB> symbol, and indicates
4774  whether a C program may include Berkeley's C<DB> include file <db.h>.
4775  
4776  =item C<i_dbm>
4777  
4778  From F<i_dbm.U>:
4779  
4780  This variable conditionally defines the C<I_DBM> symbol, which
4781  indicates to the C program that <dbm.h> exists and should
4782  be included.
4783  
4784  =item C<i_dirent>
4785  
4786  From F<i_dirent.U>:
4787  
4788  This variable conditionally defines C<I_DIRENT>, which indicates
4789  to the C program that it should include <dirent.h>.
4790  
4791  =item C<i_dld>
4792  
4793  From F<i_dld.U>:
4794  
4795  This variable conditionally defines the C<I_DLD> symbol, which
4796  indicates to the C program that <dld.h> (C<GNU> dynamic loading)
4797  exists and should be included.
4798  
4799  =item C<i_dlfcn>
4800  
4801  From F<i_dlfcn.U>:
4802  
4803  This variable conditionally defines the C<I_DLFCN> symbol, which
4804  indicates to the C program that <dlfcn.h> exists and should
4805  be included.
4806  
4807  =item C<i_fcntl>
4808  
4809  From F<i_fcntl.U>:
4810  
4811  This variable controls the value of C<I_FCNTL> (which tells
4812  the C program to include <fcntl.h>).
4813  
4814  =item C<i_float>
4815  
4816  From F<i_float.U>:
4817  
4818  This variable conditionally defines the C<I_FLOAT> symbol, and indicates
4819  whether a C program may include <float.h> to get symbols like C<DBL_MAX>
4820  or C<DBL_MIN>, F<i.e>. machine dependent floating point values.
4821  
4822  =item C<i_fp>
4823  
4824  From F<i_fp.U>:
4825  
4826  This variable conditionally defines the C<I_FP> symbol, and indicates
4827  whether a C program should include <fp.h>.
4828  
4829  =item C<i_fp_class>
4830  
4831  From F<i_fp_class.U>:
4832  
4833  This variable conditionally defines the C<I_FP_CLASS> symbol, and indicates
4834  whether a C program should include <fp_class.h>.
4835  
4836  =item C<i_gdbm>
4837  
4838  From F<i_gdbm.U>:
4839  
4840  This variable conditionally defines the C<I_GDBM> symbol, which
4841  indicates to the C program that <gdbm.h> exists and should
4842  be included.
4843  
4844  =item C<i_grp>
4845  
4846  From F<i_grp.U>:
4847  
4848  This variable conditionally defines the C<I_GRP> symbol, and indicates
4849  whether a C program should include <grp.h>.
4850  
4851  =item C<i_ieeefp>
4852  
4853  From F<i_ieeefp.U>:
4854  
4855  This variable conditionally defines the C<I_IEEEFP> symbol, and indicates
4856  whether a C program should include <ieeefp.h>.
4857  
4858  =item C<i_inttypes>
4859  
4860  From F<i_inttypes.U>:
4861  
4862  This variable conditionally defines the C<I_INTTYPES> symbol,
4863  and indicates whether a C program should include <inttypes.h>.
4864  
4865  =item C<i_langinfo>
4866  
4867  From F<i_langinfo.U>:
4868  
4869  This variable conditionally defines the C<I_LANGINFO> symbol,
4870  and indicates whether a C program should include <langinfo.h>.
4871  
4872  =item C<i_libutil>
4873  
4874  From F<i_libutil.U>:
4875  
4876  This variable conditionally defines the C<I_LIBUTIL> symbol, and indicates
4877  whether a C program should include <libutil.h>.
4878  
4879  =item C<i_limits>
4880  
4881  From F<i_limits.U>:
4882  
4883  This variable conditionally defines the C<I_LIMITS> symbol, and indicates
4884  whether a C program may include <limits.h> to get symbols like C<WORD_BIT>
4885  and friends.
4886  
4887  =item C<i_locale>
4888  
4889  From F<i_locale.U>:
4890  
4891  This variable conditionally defines the C<I_LOCALE> symbol,
4892  and indicates whether a C program should include <locale.h>.
4893  
4894  =item C<i_machcthr>
4895  
4896  From F<i_machcthr.U>:
4897  
4898  This variable conditionally defines the C<I_MACH_CTHREADS> symbol,
4899  and indicates whether a C program should include <mach/cthreads.h>.
4900  
4901  =item C<i_malloc>
4902  
4903  From F<i_malloc.U>:
4904  
4905  This variable conditionally defines the C<I_MALLOC> symbol, and indicates
4906  whether a C program should include <malloc.h>.
4907  
4908  =item C<i_math>
4909  
4910  From F<i_math.U>:
4911  
4912  This variable conditionally defines the C<I_MATH> symbol, and indicates
4913  whether a C program may include <math.h>.
4914  
4915  =item C<i_memory>
4916  
4917  From F<i_memory.U>:
4918  
4919  This variable conditionally defines the C<I_MEMORY> symbol, and indicates
4920  whether a C program should include <memory.h>.
4921  
4922  =item C<i_mntent>
4923  
4924  From F<i_mntent.U>:
4925  
4926  This variable conditionally defines the C<I_MNTENT> symbol, and indicates
4927  whether a C program should include <mntent.h>.
4928  
4929  =item C<i_ndbm>
4930  
4931  From F<i_ndbm.U>:
4932  
4933  This variable conditionally defines the C<I_NDBM> symbol, which
4934  indicates to the C program that <ndbm.h> exists and should
4935  be included.
4936  
4937  =item C<i_netdb>
4938  
4939  From F<i_netdb.U>:
4940  
4941  This variable conditionally defines the C<I_NETDB> symbol, and indicates
4942  whether a C program should include <netdb.h>.
4943  
4944  =item C<i_neterrno>
4945  
4946  From F<i_neterrno.U>:
4947  
4948  This variable conditionally defines the C<I_NET_ERRNO> symbol, which
4949  indicates to the C program that <net/errno.h> exists and should
4950  be included.
4951  
4952  =item C<i_netinettcp>
4953  
4954  From F<i_netinettcp.U>:
4955  
4956  This variable conditionally defines the C<I_NETINET_TCP> symbol,
4957  and indicates whether a C program should include <netinet/tcp.h>.
4958  
4959  =item C<i_niin>
4960  
4961  From F<i_niin.U>:
4962  
4963  This variable conditionally defines C<I_NETINET_IN>, which indicates
4964  to the C program that it should include <netinet/in.h>. Otherwise,
4965  you may try <sys/in.h>.
4966  
4967  =item C<i_poll>
4968  
4969  From F<i_poll.U>:
4970  
4971  This variable conditionally defines the C<I_POLL> symbol, and indicates
4972  whether a C program should include <poll.h>.
4973  
4974  =item C<i_prot>
4975  
4976  From F<i_prot.U>:
4977  
4978  This variable conditionally defines the C<I_PROT> symbol, and indicates
4979  whether a C program should include <prot.h>.
4980  
4981  =item C<i_pthread>
4982  
4983  From F<i_pthread.U>:
4984  
4985  This variable conditionally defines the C<I_PTHREAD> symbol,
4986  and indicates whether a C program should include <pthread.h>.
4987  
4988  =item C<i_pwd>
4989  
4990  From F<i_pwd.U>:
4991  
4992  This variable conditionally defines C<I_PWD>, which indicates
4993  to the C program that it should include <pwd.h>.
4994  
4995  =item C<i_rpcsvcdbm>
4996  
4997  From F<i_dbm.U>:
4998  
4999  This variable conditionally defines the C<I_RPCSVC_DBM> symbol, which
5000  indicates to the C program that <rpcsvc/dbm.h> exists and should
5001  be included.  Some System V systems might need this instead of <dbm.h>.
5002  
5003  =item C<i_sfio>
5004  
5005  From F<i_sfio.U>:
5006  
5007  This variable conditionally defines the C<I_SFIO> symbol,
5008  and indicates whether a C program should include <sfio.h>.
5009  
5010  =item C<i_sgtty>
5011  
5012  From F<i_termio.U>:
5013  
5014  This variable conditionally defines the C<I_SGTTY> symbol, which
5015  indicates to the C program that it should include <sgtty.h> rather
5016  than <termio.h>.
5017  
5018  =item C<i_shadow>
5019  
5020  From F<i_shadow.U>:
5021  
5022  This variable conditionally defines the C<I_SHADOW> symbol, and indicates
5023  whether a C program should include <shadow.h>.
5024  
5025  =item C<i_socks>
5026  
5027  From F<i_socks.U>:
5028  
5029  This variable conditionally defines the C<I_SOCKS> symbol, and indicates
5030  whether a C program should include <socks.h>.
5031  
5032  =item C<i_stdarg>
5033  
5034  From F<i_varhdr.U>:
5035  
5036  This variable conditionally defines the C<I_STDARG> symbol, which
5037  indicates to the C program that <stdarg.h> exists and should
5038  be included.
5039  
5040  =item C<i_stddef>
5041  
5042  From F<i_stddef.U>:
5043  
5044  This variable conditionally defines the C<I_STDDEF> symbol, which
5045  indicates to the C program that <stddef.h> exists and should
5046  be included.
5047  
5048  =item C<i_stdlib>
5049  
5050  From F<i_stdlib.U>:
5051  
5052  This variable conditionally defines the C<I_STDLIB> symbol, which
5053  indicates to the C program that <stdlib.h> exists and should
5054  be included.
5055  
5056  =item C<i_string>
5057  
5058  From F<i_string.U>:
5059  
5060  This variable conditionally defines the C<I_STRING> symbol, which
5061  indicates that <string.h> should be included rather than <strings.h>.
5062  
5063  =item C<i_sunmath>
5064  
5065  From F<i_sunmath.U>:
5066  
5067  This variable conditionally defines the C<I_SUNMATH> symbol, and indicates
5068  whether a C program should include <sunmath.h>.
5069  
5070  =item C<i_sysaccess>
5071  
5072  From F<i_sysaccess.U>:
5073  
5074  This variable conditionally defines the C<I_SYS_ACCESS> symbol,
5075  and indicates whether a C program should include <sys/access.h>.
5076  
5077  =item C<i_sysdir>
5078  
5079  From F<i_sysdir.U>:
5080  
5081  This variable conditionally defines the C<I_SYS_DIR> symbol, and indicates
5082  whether a C program should include <sys/dir.h>.
5083  
5084  =item C<i_sysfile>
5085  
5086  From F<i_sysfile.U>:
5087  
5088  This variable conditionally defines the C<I_SYS_FILE> symbol, and indicates
5089  whether a C program should include <sys/file.h> to get C<R_OK> and friends.
5090  
5091  =item C<i_sysfilio>
5092  
5093  From F<i_sysioctl.U>:
5094  
5095  This variable conditionally defines the C<I_SYS_FILIO> symbol, which
5096  indicates to the C program that <sys/filio.h> exists and should
5097  be included in preference to <sys/ioctl.h>.
5098  
5099  =item C<i_sysin>
5100  
5101  From F<i_niin.U>:
5102  
5103  This variable conditionally defines C<I_SYS_IN>, which indicates
5104  to the C program that it should include <sys/in.h> instead of
5105  <netinet/in.h>.
5106  
5107  =item C<i_sysioctl>
5108  
5109  From F<i_sysioctl.U>:
5110  
5111  This variable conditionally defines the C<I_SYS_IOCTL> symbol, which
5112  indicates to the C program that <sys/ioctl.h> exists and should
5113  be included.
5114  
5115  =item C<i_syslog>
5116  
5117  From F<i_syslog.U>:
5118  
5119  This variable conditionally defines the C<I_SYSLOG> symbol,
5120  and indicates whether a C program should include <syslog.h>.
5121  
5122  =item C<i_sysmman>
5123  
5124  From F<i_sysmman.U>:
5125  
5126  This variable conditionally defines the C<I_SYS_MMAN> symbol, and
5127  indicates whether a C program should include <sys/mman.h>.
5128  
5129  =item C<i_sysmode>
5130  
5131  From F<i_sysmode.U>:
5132  
5133  This variable conditionally defines the C<I_SYSMODE> symbol,
5134  and indicates whether a C program should include <sys/mode.h>.
5135  
5136  =item C<i_sysmount>
5137  
5138  From F<i_sysmount.U>:
5139  
5140  This variable conditionally defines the C<I_SYSMOUNT> symbol,
5141  and indicates whether a C program should include <sys/mount.h>.
5142  
5143  =item C<i_sysndir>
5144  
5145  From F<i_sysndir.U>:
5146  
5147  This variable conditionally defines the C<I_SYS_NDIR> symbol, and indicates
5148  whether a C program should include <sys/ndir.h>.
5149  
5150  =item C<i_sysparam>
5151  
5152  From F<i_sysparam.U>:
5153  
5154  This variable conditionally defines the C<I_SYS_PARAM> symbol, and indicates
5155  whether a C program should include <sys/param.h>.
5156  
5157  =item C<i_sysresrc>
5158  
5159  From F<i_sysresrc.U>:
5160  
5161  This variable conditionally defines the C<I_SYS_RESOURCE> symbol,
5162  and indicates whether a C program should include <sys/resource.h>.
5163  
5164  =item C<i_syssecrt>
5165  
5166  From F<i_syssecrt.U>:
5167  
5168  This variable conditionally defines the C<I_SYS_SECURITY> symbol,
5169  and indicates whether a C program should include <sys/security.h>.
5170  
5171  =item C<i_sysselct>
5172  
5173  From F<i_sysselct.U>:
5174  
5175  This variable conditionally defines C<I_SYS_SELECT>, which indicates
5176  to the C program that it should include <sys/select.h> in order to
5177  get the definition of struct timeval.
5178  
5179  =item C<i_syssockio>
5180  
5181  From F<i_sysioctl.U>:
5182  
5183  This variable conditionally defines C<I_SYS_SOCKIO> to indicate to the
5184  C program that socket ioctl codes may be found in <sys/sockio.h>
5185  instead of <sys/ioctl.h>.
5186  
5187  =item C<i_sysstat>
5188  
5189  From F<i_sysstat.U>:
5190  
5191  This variable conditionally defines the C<I_SYS_STAT> symbol,
5192  and indicates whether a C program should include <sys/stat.h>.
5193  
5194  =item C<i_sysstatfs>
5195  
5196  From F<i_sysstatfs.U>:
5197  
5198  This variable conditionally defines the C<I_SYSSTATFS> symbol,
5199  and indicates whether a C program should include <sys/statfs.h>.
5200  
5201  =item C<i_sysstatvfs>
5202  
5203  From F<i_sysstatvfs.U>:
5204  
5205  This variable conditionally defines the C<I_SYSSTATVFS> symbol,
5206  and indicates whether a C program should include <sys/statvfs.h>.
5207  
5208  =item C<i_systime>
5209  
5210  From F<i_time.U>:
5211  
5212  This variable conditionally defines C<I_SYS_TIME>, which indicates
5213  to the C program that it should include <sys/time.h>.
5214  
5215  =item C<i_systimek>
5216  
5217  From F<i_time.U>:
5218  
5219  This variable conditionally defines C<I_SYS_TIME_KERNEL>, which
5220  indicates to the C program that it should include <sys/time.h>
5221  with C<KERNEL> defined.
5222  
5223  =item C<i_systimes>
5224  
5225  From F<i_systimes.U>:
5226  
5227  This variable conditionally defines the C<I_SYS_TIMES> symbol, and indicates
5228  whether a C program should include <sys/times.h>.
5229  
5230  =item C<i_systypes>
5231  
5232  From F<i_systypes.U>:
5233  
5234  This variable conditionally defines the C<I_SYS_TYPES> symbol,
5235  and indicates whether a C program should include <sys/types.h>.
5236  
5237  =item C<i_sysuio>
5238  
5239  From F<i_sysuio.U>:
5240  
5241  This variable conditionally defines the C<I_SYSUIO> symbol, and indicates
5242  whether a C program should include <sys/uio.h>.
5243  
5244  =item C<i_sysun>
5245  
5246  From F<i_sysun.U>:
5247  
5248  This variable conditionally defines C<I_SYS_UN>, which indicates
5249  to the C program that it should include <sys/un.h> to get C<UNIX>
5250  domain socket definitions.
5251  
5252  =item C<i_sysutsname>
5253  
5254  From F<i_sysutsname.U>:
5255  
5256  This variable conditionally defines the C<I_SYSUTSNAME> symbol,
5257  and indicates whether a C program should include <sys/utsname.h>.
5258  
5259  =item C<i_sysvfs>
5260  
5261  From F<i_sysvfs.U>:
5262  
5263  This variable conditionally defines the C<I_SYSVFS> symbol,
5264  and indicates whether a C program should include <sys/vfs.h>.
5265  
5266  =item C<i_syswait>
5267  
5268  From F<i_syswait.U>:
5269  
5270  This variable conditionally defines C<I_SYS_WAIT>, which indicates
5271  to the C program that it should include <sys/wait.h>.
5272  
5273  =item C<i_termio>
5274  
5275  From F<i_termio.U>:
5276  
5277  This variable conditionally defines the C<I_TERMIO> symbol, which
5278  indicates to the C program that it should include <termio.h> rather
5279  than <sgtty.h>.
5280  
5281  =item C<i_termios>
5282  
5283  From F<i_termio.U>:
5284  
5285  This variable conditionally defines the C<I_TERMIOS> symbol, which
5286  indicates to the C program that the C<POSIX> <termios.h> file is
5287  to be included.
5288  
5289  =item C<i_time>
5290  
5291  From F<i_time.U>:
5292  
5293  This variable conditionally defines C<I_TIME>, which indicates
5294  to the C program that it should include <time.h>.
5295  
5296  =item C<i_unistd>
5297  
5298  From F<i_unistd.U>:
5299  
5300  This variable conditionally defines the C<I_UNISTD> symbol, and indicates
5301  whether a C program should include <unistd.h>.
5302  
5303  =item C<i_ustat>
5304  
5305  From F<i_ustat.U>:
5306  
5307  This variable conditionally defines the C<I_USTAT> symbol, and indicates
5308  whether a C program should include <ustat.h>.
5309  
5310  =item C<i_utime>
5311  
5312  From F<i_utime.U>:
5313  
5314  This variable conditionally defines the C<I_UTIME> symbol, and indicates
5315  whether a C program should include <utime.h>.
5316  
5317  =item C<i_values>
5318  
5319  From F<i_values.U>:
5320  
5321  This variable conditionally defines the C<I_VALUES> symbol, and indicates
5322  whether a C program may include <values.h> to get symbols like C<MAXLONG>
5323  and friends.
5324  
5325  =item C<i_varargs>
5326  
5327  From F<i_varhdr.U>:
5328  
5329  This variable conditionally defines C<I_VARARGS>, which indicates
5330  to the C program that it should include <varargs.h>.
5331  
5332  =item C<i_varhdr>
5333  
5334  From F<i_varhdr.U>:
5335  
5336  Contains the name of the header to be included to get va_dcl definition.
5337  Typically one of F<varargs.h> or F<stdarg.h>.
5338  
5339  =item C<i_vfork>
5340  
5341  From F<i_vfork.U>:
5342  
5343  This variable conditionally defines the C<I_VFORK> symbol, and indicates
5344  whether a C program should include F<vfork.h>.
5345  
5346  =item C<ignore_versioned_solibs>
5347  
5348  From F<libs.U>:
5349  
5350  This variable should be non-empty if non-versioned shared
5351  libraries (F<libfoo.so.x.y>) are to be ignored (because they
5352  cannot be linked against).
5353  
5354  =item C<inc_version_list>
5355  
5356  From F<inc_version_list.U>:
5357  
5358  This variable specifies the list of subdirectories in over
5359  which F<perl.c>:incpush() and F<lib/lib.pm> will automatically
5360  search when adding directories to @C<INC>.  The elements in
5361  the list are separated by spaces.  This is only useful
5362  if you have a perl library directory tree structured like the
5363  default one.  See C<INSTALL> for how this works.  The versioned
5364  site_perl directory was introduced in 5.005, so that is the
5365  lowest possible value.
5366  
5367  This list includes architecture-dependent directories back to
5368  version $api_versionstring (e.g. 5.5.640) and
5369  architecture-independent directories all the way back to
5370  5.005.
5371  
5372  =item C<inc_version_list_init>
5373  
5374  From F<inc_version_list.U>:
5375  
5376  This variable holds the same list as inc_version_list, but
5377  each item is enclosed in double quotes and separated by commas,
5378  suitable for use in the C<PERL_INC_VERSION_LIST> initialization.
5379  
5380  =item C<incpath>
5381  
5382  From F<usrinc.U>:
5383  
5384  This variable must preceed the normal include path to get hte
5385  right one, as in F<$F<incpath/usr/include>> or F<$F<incpath/usr/lib>>.
5386  Value can be "" or F</bsd43> on mips.
5387  
5388  =item C<inews>
5389  
5390  From F<Loc.U>:
5391  
5392  This variable is defined but not used by Configure.
5393  The value is a plain '' and is not useful.
5394  
5395  =item C<initialinstalllocation>
5396  
5397  From F<bin.U>:
5398  
5399  When userelocatableinc is true, this variable holds the location
5400  that make install should copy the perl binary to, with all the
5401  run-time relocatable paths calculated from this at install time.
5402  When used, it is initialised to the original value of binexp, and
5403  then binexp is set to F<.../>, as the other binaries are found
5404  relative to the perl binary.
5405  
5406  =item C<installarchlib>
5407  
5408  From F<archlib.U>:
5409  
5410  This variable is really the same as archlibexp but may differ on
5411  those systems using C<AFS>. For extra portability, only this variable
5412  should be used in makefiles.
5413  
5414  =item C<installbin>
5415  
5416  From F<bin.U>:
5417  
5418  This variable is the same as binexp unless C<AFS> is running in which case
5419  the user is explicitely prompted for it. This variable should always
5420  be used in your makefiles for maximum portability.
5421  
5422  =item C<installhtml1dir>
5423  
5424  From F<html1dir.U>:
5425  
5426  This variable is really the same as html1direxp, unless you are
5427  using a different installprefix.  For extra portability, you
5428  should only use this variable within your makefiles.
5429  
5430  =item C<installhtml3dir>
5431  
5432  From F<html3dir.U>:
5433  
5434  This variable is really the same as html3direxp, unless you are
5435  using a different installprefix.  For extra portability, you
5436  should only use this variable within your makefiles.
5437  
5438  =item C<installman1dir>
5439  
5440  From F<man1dir.U>:
5441  
5442  This variable is really the same as man1direxp, unless you are using
5443  C<AFS> in which case it points to the read/write location whereas
5444  man1direxp only points to the read-only access location. For extra
5445  portability, you should only use this variable within your makefiles.
5446  
5447  =item C<installman3dir>
5448  
5449  From F<man3dir.U>:
5450  
5451  This variable is really the same as man3direxp, unless you are using
5452  C<AFS> in which case it points to the read/write location whereas
5453  man3direxp only points to the read-only access location. For extra
5454  portability, you should only use this variable within your makefiles.
5455  
5456  =item C<installprefix>
5457  
5458  From F<installprefix.U>:
5459  
5460  This variable holds the name of the directory below which
5461  "make install" will install the package.  For most users, this
5462  is the same as prefix.  However, it is useful for
5463  installing the software into a different (usually temporary)
5464  location after which it can be bundled up and moved somehow
5465  to the final location specified by prefix.
5466  
5467  =item C<installprefixexp>
5468  
5469  From F<installprefix.U>:
5470  
5471  This variable holds the full absolute path of installprefix
5472  with all F<~>-expansion done.
5473  
5474  =item C<installprivlib>
5475  
5476  From F<privlib.U>:
5477  
5478  This variable is really the same as privlibexp but may differ on
5479  those systems using C<AFS>. For extra portability, only this variable
5480  should be used in makefiles.
5481  
5482  =item C<installscript>
5483  
5484  From F<scriptdir.U>:
5485  
5486  This variable is usually the same as scriptdirexp, unless you are on
5487  a system running C<AFS>, in which case they may differ slightly. You
5488  should always use this variable within your makefiles for portability.
5489  
5490  =item C<installsitearch>
5491  
5492  From F<sitearch.U>:
5493  
5494  This variable is really the same as sitearchexp but may differ on
5495  those systems using C<AFS>. For extra portability, only this variable
5496  should be used in makefiles.
5497  
5498  =item C<installsitebin>
5499  
5500  From F<sitebin.U>:
5501  
5502  This variable is usually the same as sitebinexp, unless you are on
5503  a system running C<AFS>, in which case they may differ slightly. You
5504  should always use this variable within your makefiles for portability.
5505  
5506  =item C<installsitehtml1dir>
5507  
5508  From F<sitehtml1dir.U>:
5509  
5510  This variable is really the same as sitehtml1direxp, unless you are using
5511  C<AFS> in which case it points to the read/write location whereas
5512  html1direxp only points to the read-only access location. For extra
5513  portability, you should only use this variable within your makefiles.
5514  
5515  =item C<installsitehtml3dir>
5516  
5517  From F<sitehtml3dir.U>:
5518  
5519  This variable is really the same as sitehtml3direxp, unless you are using
5520  C<AFS> in which case it points to the read/write location whereas
5521  html3direxp only points to the read-only access location. For extra
5522  portability, you should only use this variable within your makefiles.
5523  
5524  =item C<installsitelib>
5525  
5526  From F<sitelib.U>:
5527  
5528  This variable is really the same as sitelibexp but may differ on
5529  those systems using C<AFS>. For extra portability, only this variable
5530  should be used in makefiles.
5531  
5532  =item C<installsiteman1dir>
5533  
5534  From F<siteman1dir.U>:
5535  
5536  This variable is really the same as siteman1direxp, unless you are using
5537  C<AFS> in which case it points to the read/write location whereas
5538  man1direxp only points to the read-only access location. For extra
5539  portability, you should only use this variable within your makefiles.
5540  
5541  =item C<installsiteman3dir>
5542  
5543  From F<siteman3dir.U>:
5544  
5545  This variable is really the same as siteman3direxp, unless you are using
5546  C<AFS> in which case it points to the read/write location whereas
5547  man3direxp only points to the read-only access location. For extra
5548  portability, you should only use this variable within your makefiles.
5549  
5550  =item C<installsitescript>
5551  
5552  From F<sitescript.U>:
5553  
5554  This variable is usually the same as sitescriptexp, unless you are on
5555  a system running C<AFS>, in which case they may differ slightly. You
5556  should always use this variable within your makefiles for portability.
5557  
5558  =item C<installstyle>
5559  
5560  From F<installstyle.U>:
5561  
5562  This variable describes the C<style> of the perl installation.
5563  This is intended to be useful for tools that need to
5564  manipulate entire perl distributions.  Perl itself doesn't use
5565  this to find its libraries -- the library directories are
5566  stored directly in F<Config.pm>.  Currently, there are only two
5567  styles:  C<lib> and F<lib/perl5>.  The default library locations
5568  (e.g. privlib, sitelib) are either F<$prefix/lib> or
5569  F<$prefix/lib/perl5>.  The former is useful if $prefix is a
5570  directory dedicated to perl (e.g. F</opt/perl>), while the latter
5571  is useful if $prefix is shared by many packages, e.g. if
5572  $prefix=F</usr/local>.
5573  
5574  Unfortunately, while this C<style> variable is used to set
5575  defaults for all three directory hierarchies (core, vendor, and
5576  site), there is no guarantee that the same style is actually
5577  appropriate for all those directories.  For example, $prefix
5578  might be F</opt/perl>, but $siteprefix might be F</usr/local>.
5579  (Perhaps, in retrospect, the C<lib> style should never have been
5580  supported, but it did seem like a nice idea at the time.)
5581  
5582  The situation is even less clear for tools such as MakeMaker
5583  that can be used to install additional modules into
5584  non-standard places.  For example, if a user intends to install
5585  a module into a private directory (perhaps by setting C<PREFIX> on
5586  the F<Makefile.PL> command line), then there is no reason to
5587  assume that the Configure-time $installstyle setting will be
5588  relevant for that C<PREFIX>.
5589  
5590  This may later be extended to include other information, so
5591  be careful with pattern-matching on the results.
5592  
5593  For compatibility with F<perl5.005> and earlier, the default
5594  setting is based on whether or not $prefix contains the string
5595  C<perl>.
5596  
5597  =item C<installusrbinperl>
5598  
5599  From F<instubperl.U>:
5600  
5601  This variable tells whether Perl should be installed also as
5602  F</usr/bin/perl> in addition to
5603  F<$installbin/perl>
5604  
5605  =item C<installvendorarch>
5606  
5607  From F<vendorarch.U>:
5608  
5609  This variable is really the same as vendorarchexp but may differ on
5610  those systems using C<AFS>. For extra portability, only this variable
5611  should be used in makefiles.
5612  
5613  =item C<installvendorbin>
5614  
5615  From F<vendorbin.U>:
5616  
5617  This variable is really the same as vendorbinexp but may differ on
5618  those systems using C<AFS>. For extra portability, only this variable
5619  should be used in makefiles.
5620  
5621  =item C<installvendorhtml1dir>
5622  
5623  From F<vendorhtml1dir.U>:
5624  
5625  This variable is really the same as vendorhtml1direxp but may differ on
5626  those systems using C<AFS>. For extra portability, only this variable
5627  should be used in makefiles.
5628  
5629  =item C<installvendorhtml3dir>
5630  
5631  From F<vendorhtml3dir.U>:
5632  
5633  This variable is really the same as vendorhtml3direxp but may differ on
5634  those systems using C<AFS>. For extra portability, only this variable
5635  should be used in makefiles.
5636  
5637  =item C<installvendorlib>
5638  
5639  From F<vendorlib.U>:
5640  
5641  This variable is really the same as vendorlibexp but may differ on
5642  those systems using C<AFS>. For extra portability, only this variable
5643  should be used in makefiles.
5644  
5645  =item C<installvendorman1dir>
5646  
5647  From F<vendorman1dir.U>:
5648  
5649  This variable is really the same as vendorman1direxp but may differ on
5650  those systems using C<AFS>. For extra portability, only this variable
5651  should be used in makefiles.
5652  
5653  =item C<installvendorman3dir>
5654  
5655  From F<vendorman3dir.U>:
5656  
5657  This variable is really the same as vendorman3direxp but may differ on
5658  those systems using C<AFS>. For extra portability, only this variable
5659  should be used in makefiles.
5660  
5661  =item C<installvendorscript>
5662  
5663  From F<vendorscript.U>:
5664  
5665  This variable is really the same as vendorscriptexp but may differ on
5666  those systems using C<AFS>. For extra portability, only this variable
5667  should be used in makefiles.
5668  
5669  =item C<intsize>
5670  
5671  From F<intsize.U>:
5672  
5673  This variable contains the value of the C<INTSIZE> symbol, which
5674  indicates to the C program how many bytes there are in an int.
5675  
5676  =item C<issymlink>
5677  
5678  From F<issymlink.U>:
5679  
5680  This variable holds the test command to test for a symbolic link
5681  (if they are supported).  Typical values include C<test -h> and
5682  C<test -L>.
5683  
5684  =item C<ivdformat>
5685  
5686  From F<perlxvf.U>:
5687  
5688  This variable contains the format string used for printing
5689  a Perl C<IV> as a signed decimal integer.
5690  
5691  =item C<ivsize>
5692  
5693  From F<perlxv.U>:
5694  
5695  This variable is the size of an C<IV> in bytes.
5696  
5697  =item C<ivtype>
5698  
5699  From F<perlxv.U>:
5700  
5701  This variable contains the C type used for Perl's C<IV>.
5702  
5703  =back
5704  
5705  =head2 k
5706  
5707  =over 4
5708  
5709  =item C<known_extensions>
5710  
5711  From F<Extensions.U>:
5712  
5713  This variable holds a list of all C<XS> extensions included in
5714  the package.
5715  
5716  =item C<ksh>
5717  
5718  From F<Loc.U>:
5719  
5720  This variable is defined but not used by Configure.
5721  The value is a plain '' and is not useful.
5722  
5723  =back
5724  
5725  =head2 l
5726  
5727  =over 4
5728  
5729  =item C<ld>
5730  
5731  From F<dlsrc.U>:
5732  
5733  This variable indicates the program to be used to link
5734  libraries for dynamic loading.  On some systems, it is C<ld>.
5735  On C<ELF> systems, it should be $cc.  Mostly, we'll try to respect
5736  the hint file setting.
5737  
5738  =item C<lddlflags>
5739  
5740  From F<dlsrc.U>:
5741  
5742  This variable contains any special flags that might need to be
5743  passed to $ld to create a shared library suitable for dynamic
5744  loading.  It is up to the makefile to use it.  For hpux, it
5745  should be C<-b>.  For sunos 4.1, it is empty.
5746  
5747  =item C<ldflags>
5748  
5749  From F<ccflags.U>:
5750  
5751  This variable contains any additional C loader flags desired by
5752  the user.  It is up to the Makefile to use this.
5753  
5754  =item C<ldflags_uselargefiles>
5755  
5756  From F<uselfs.U>:
5757  
5758  This variable contains the loader flags needed by large file builds
5759  and added to ldflags by hints files.
5760  
5761  =item C<ldlibpthname>
5762  
5763  From F<libperl.U>:
5764  
5765  This variable holds the name of the shared library
5766  search path, often C<LD_LIBRARY_PATH>.  To get an empty
5767  string, the hints file must set this to C<none>.
5768  
5769  =item C<less>
5770  
5771  From F<Loc.U>:
5772  
5773  This variable is used internally by Configure to determine the
5774  full pathname (if any) of the less program.  After Configure runs,
5775  the value is reset to a plain C<less> and is not useful.
5776  
5777  =item C<lib_ext>
5778  
5779  From F<Unix.U>:
5780  
5781  This is an old synonym for _a.
5782  
5783  =item C<libc>
5784  
5785  From F<libc.U>:
5786  
5787  This variable contains the location of the C library.
5788  
5789  =item C<libperl>
5790  
5791  From F<libperl.U>:
5792  
5793  The perl executable is obtained by linking F<perlmain.c> with
5794  libperl, any static extensions (usually just DynaLoader),
5795  and any other libraries needed on this system.  libperl
5796  is usually F<libperl.a>, but can also be F<libperl.so.xxx> if
5797  the user wishes to build a perl executable with a shared
5798  library.
5799  
5800  =item C<libpth>
5801  
5802  From F<libpth.U>:
5803  
5804  This variable holds the general path (space-separated) used to find
5805  libraries. It is intended to be used by other units.
5806  
5807  =item C<libs>
5808  
5809  From F<libs.U>:
5810  
5811  This variable holds the additional libraries we want to use.
5812  It is up to the Makefile to deal with it.  The list can be empty.
5813  
5814  =item C<libsdirs>
5815  
5816  From F<libs.U>:
5817  
5818  This variable holds the directory names aka dirnames of the libraries
5819  we found and accepted, duplicates are removed.
5820  
5821  =item C<libsfiles>
5822  
5823  From F<libs.U>:
5824  
5825  This variable holds the filenames aka basenames of the libraries
5826  we found and accepted.
5827  
5828  =item C<libsfound>
5829  
5830  From F<libs.U>:
5831  
5832  This variable holds the full pathnames of the libraries
5833  we found and accepted.
5834  
5835  =item C<libspath>
5836  
5837  From F<libs.U>:
5838  
5839  This variable holds the directory names probed for libraries.
5840  
5841  =item C<libswanted>
5842  
5843  From F<Myinit.U>:
5844  
5845  This variable holds a list of all the libraries we want to
5846  search.  The order is chosen to pick up the c library
5847  ahead of ucb or bsd libraries for SVR4.
5848  
5849  =item C<libswanted_uselargefiles>
5850  
5851  From F<uselfs.U>:
5852  
5853  This variable contains the libraries needed by large file builds
5854  and added to ldflags by hints files.  It is a space separated list
5855  of the library names without the C<lib> prefix or any suffix, just
5856  like F<libswanted.>.
5857  
5858  =item C<line>
5859  
5860  From F<Loc.U>:
5861  
5862  This variable is defined but not used by Configure.
5863  The value is a plain '' and is not useful.
5864  
5865  =item C<lint>
5866  
5867  From F<Loc.U>:
5868  
5869  This variable is defined but not used by Configure.
5870  The value is a plain '' and is not useful.
5871  
5872  =item C<lkflags>
5873  
5874  From F<ccflags.U>:
5875  
5876  This variable contains any additional C partial linker flags desired by
5877  the user.  It is up to the Makefile to use this.
5878  
5879  =item C<ln>
5880  
5881  From F<Loc.U>:
5882  
5883  This variable is used internally by Configure to determine the
5884  full pathname (if any) of the ln program.  After Configure runs,
5885  the value is reset to a plain C<ln> and is not useful.
5886  
5887  =item C<lns>
5888  
5889  From F<lns.U>:
5890  
5891  This variable holds the name of the command to make
5892  symbolic links (if they are supported).  It can be used
5893  in the Makefile. It is either C<ln -s> or C<ln>
5894  
5895  =item C<localtime_r_proto>
5896  
5897  From F<d_localtime_r.U>:
5898  
5899  This variable encodes the prototype of localtime_r.
5900  It is zero if d_localtime_r is undef, and one of the
5901  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_localtime_r
5902  is defined.
5903  
5904  =item C<locincpth>
5905  
5906  From F<ccflags.U>:
5907  
5908  This variable contains a list of additional directories to be
5909  searched by the compiler.  The appropriate C<-I> directives will
5910  be added to ccflags.  This is intended to simplify setting
5911  local directories from the Configure command line.
5912  It's not much, but it parallels the loclibpth stuff in F<libpth.U>.
5913  
5914  =item C<loclibpth>
5915  
5916  From F<libpth.U>:
5917  
5918  This variable holds the paths (space-separated) used to find local
5919  libraries.  It is prepended to libpth, and is intended to be easily
5920  set from the command line.
5921  
5922  =item C<longdblsize>
5923  
5924  From F<d_longdbl.U>:
5925  
5926  This variable contains the value of the C<LONG_DOUBLESIZE> symbol, which
5927  indicates to the C program how many bytes there are in a long double,
5928  if this system supports long doubles.
5929  
5930  =item C<longlongsize>
5931  
5932  From F<d_longlong.U>:
5933  
5934  This variable contains the value of the C<LONGLONGSIZE> symbol, which
5935  indicates to the C program how many bytes there are in a long long,
5936  if this system supports long long.
5937  
5938  =item C<longsize>
5939  
5940  From F<intsize.U>:
5941  
5942  This variable contains the value of the C<LONGSIZE> symbol, which
5943  indicates to the C program how many bytes there are in a long.
5944  
5945  =item C<lp>
5946  
5947  From F<Loc.U>:
5948  
5949  This variable is defined but not used by Configure.
5950  The value is a plain '' and is not useful.
5951  
5952  =item C<lpr>
5953  
5954  From F<Loc.U>:
5955  
5956  This variable is defined but not used by Configure.
5957  The value is a plain '' and is not useful.
5958  
5959  =item C<ls>
5960  
5961  From F<Loc.U>:
5962  
5963  This variable is used internally by Configure to determine the
5964  full pathname (if any) of the ls program.  After Configure runs,
5965  the value is reset to a plain C<ls> and is not useful.
5966  
5967  =item C<lseeksize>
5968  
5969  From F<lseektype.U>:
5970  
5971  This variable defines lseektype to be something like off_t, long,
5972  or whatever type is used to declare lseek offset's type in the
5973  kernel (which also appears to be lseek's return type).
5974  
5975  =item C<lseektype>
5976  
5977  From F<lseektype.U>:
5978  
5979  This variable defines lseektype to be something like off_t, long,
5980  or whatever type is used to declare lseek offset's type in the
5981  kernel (which also appears to be lseek's return type).
5982  
5983  =back
5984  
5985  =head2 m
5986  
5987  =over 4
5988  
5989  =item C<mad>
5990  
5991  From F<mad.U>:
5992  
5993  This variable indicates that the Misc Attribute Definition code is to
5994  be compiled.
5995  
5996  =item C<madlyh>
5997  
5998  From F<mad.U>:
5999  
6000  If the Misc Attribute Decoration is to be compiled, this variable is
6001  set to the name of the extra header files to be used, else it is ''
6002  
6003  =item C<madlyobj>
6004  
6005  From F<mad.U>:
6006  
6007  If the Misc Attribute Decoration is to be compiled, this variable is
6008  set to the name of the extra object files to be used, else it is ''
6009  
6010  =item C<madlysrc>
6011  
6012  From F<mad.U>:
6013  
6014  If the Misc Attribute Decoration is to be compiled, this variable is
6015  set to the name of the extra C source files to be used, else it is ''
6016  
6017  =item C<mail>
6018  
6019  From F<Loc.U>:
6020  
6021  This variable is defined but not used by Configure.
6022  The value is a plain '' and is not useful.
6023  
6024  =item C<mailx>
6025  
6026  From F<Loc.U>:
6027  
6028  This variable is defined but not used by Configure.
6029  The value is a plain '' and is not useful.
6030  
6031  =item C<make>
6032  
6033  From F<Loc.U>:
6034  
6035  This variable is used internally by Configure to determine the
6036  full pathname (if any) of the make program.  After Configure runs,
6037  the value is reset to a plain C<make> and is not useful.
6038  
6039  =item C<make_set_make>
6040  
6041  From F<make.U>:
6042  
6043  Some versions of C<make> set the variable C<MAKE>.  Others do not.
6044  This variable contains the string to be included in F<Makefile.SH>
6045  so that C<MAKE> is set if needed, and not if not needed.
6046  Possible values are:
6047  
6048  make_set_make=C<#>        # If your make program handles this for you,
6049  
6050  make_set_make=C<MAKE=$make>    # if it doesn't.
6051  
6052  This uses a comment character to distinguish a
6053  C<set> value (from a previous F<config.sh> or Configure C<-D> option)
6054  from an uncomputed value.
6055  
6056  =item C<mallocobj>
6057  
6058  From F<mallocsrc.U>:
6059  
6060  This variable contains the name of the F<malloc.o> that this package
6061  generates, if that F<malloc.o> is preferred over the system malloc.
6062  Otherwise the value is null.  This variable is intended for generating
6063  Makefiles.  See mallocsrc.
6064  
6065  =item C<mallocsrc>
6066  
6067  From F<mallocsrc.U>:
6068  
6069  This variable contains the name of the F<malloc.c> that comes with
6070  the package, if that F<malloc.c> is preferred over the system malloc.
6071  Otherwise the value is null.  This variable is intended for generating
6072  Makefiles.
6073  
6074  =item C<malloctype>
6075  
6076  From F<mallocsrc.U>:
6077  
6078  This variable contains the kind of ptr returned by malloc and realloc.
6079  
6080  =item C<man1dir>
6081  
6082  From F<man1dir.U>:
6083  
6084  This variable contains the name of the directory in which manual
6085  source pages are to be put.  It is the responsibility of the
6086  F<Makefile.SH> to get the value of this into the proper command.
6087  You must be prepared to do the F<~name> expansion yourself.
6088  
6089  =item C<man1direxp>
6090  
6091  From F<man1dir.U>:
6092  
6093  This variable is the same as the man1dir variable, but is filename
6094  expanded at configuration time, for convenient use in makefiles.
6095  
6096  =item C<man1ext>
6097  
6098  From F<man1dir.U>:
6099  
6100  This variable contains the extension that the manual page should
6101  have: one of C<n>, C<l>, or C<1>.  The Makefile must supply the F<.>.
6102  See man1dir.
6103  
6104  =item C<man3dir>
6105  
6106  From F<man3dir.U>:
6107  
6108  This variable contains the name of the directory in which manual
6109  source pages are to be put.  It is the responsibility of the
6110  F<Makefile.SH> to get the value of this into the proper command.
6111  You must be prepared to do the F<~name> expansion yourself.
6112  
6113  =item C<man3direxp>
6114  
6115  From F<man3dir.U>:
6116  
6117  This variable is the same as the man3dir variable, but is filename
6118  expanded at configuration time, for convenient use in makefiles.
6119  
6120  =item C<man3ext>
6121  
6122  From F<man3dir.U>:
6123  
6124  This variable contains the extension that the manual page should
6125  have: one of C<n>, C<l>, or C<3>.  The Makefile must supply the F<.>.
6126  See man3dir.
6127  
6128  =back
6129  
6130  =head2 M
6131  
6132  =over 4
6133  
6134  =item C<Mcc>
6135  
6136  From F<Loc.U>:
6137  
6138  This variable is used internally by Configure to determine the
6139  full pathname (if any) of the Mcc program.  After Configure runs,
6140  the value is reset to a plain C<Mcc> and is not useful.
6141  
6142  =item C<mips_type>
6143  
6144  From F<usrinc.U>:
6145  
6146  This variable holds the environment type for the mips system.
6147  Possible values are "BSD 4.3" and "System V".
6148  
6149  =item C<mistrustnm>
6150  
6151  From F<Csym.U>:
6152  
6153  This variable can be used to establish a fallthrough for the cases
6154  where nm fails to find a symbol.  If usenm is false or usenm is true
6155  and mistrustnm is false, this variable has no effect.  If usenm is true
6156  and mistrustnm is C<compile>, a test program will be compiled to try to
6157  find any symbol that can't be located via nm lookup.  If mistrustnm is
6158  C<run>, the test program will be run as well as being compiled.
6159  
6160  =item C<mkdir>
6161  
6162  From F<Loc.U>:
6163  
6164  This variable is used internally by Configure to determine the
6165  full pathname (if any) of the mkdir program.  After Configure runs,
6166  the value is reset to a plain C<mkdir> and is not useful.
6167  
6168  =item C<mmaptype>
6169  
6170  From F<d_mmap.U>:
6171  
6172  This symbol contains the type of pointer returned by mmap()
6173  (and simultaneously the type of the first argument).
6174  It can be C<void *> or C<caddr_t>.
6175  
6176  =item C<modetype>
6177  
6178  From F<modetype.U>:
6179  
6180  This variable defines modetype to be something like mode_t,
6181  int, unsigned short, or whatever type is used to declare file
6182  modes for system calls.
6183  
6184  =item C<more>
6185  
6186  From F<Loc.U>:
6187  
6188  This variable is used internally by Configure to determine the
6189  full pathname (if any) of the more program.  After Configure runs,
6190  the value is reset to a plain C<more> and is not useful.
6191  
6192  =item C<multiarch>
6193  
6194  From F<multiarch.U>:
6195  
6196  This variable conditionally defines the C<MULTIARCH> symbol
6197  which signifies the presence of multiplatform files.
6198  This is normally set by hints files.
6199  
6200  =item C<mv>
6201  
6202  From F<Loc.U>:
6203  
6204  This variable is defined but not used by Configure.
6205  The value is a plain '' and is not useful.
6206  
6207  =item C<myarchname>
6208  
6209  From F<archname.U>:
6210  
6211  This variable holds the architecture name computed by Configure in
6212  a previous run. It is not intended to be perused by any user and
6213  should never be set in a hint file.
6214  
6215  =item C<mydomain>
6216  
6217  From F<myhostname.U>:
6218  
6219  This variable contains the eventual value of the C<MYDOMAIN> symbol,
6220  which is the domain of the host the program is going to run on.
6221  The domain must be appended to myhostname to form a complete host name.
6222  The dot comes with mydomain, and need not be supplied by the program.
6223  
6224  =item C<myhostname>
6225  
6226  From F<myhostname.U>:
6227  
6228  This variable contains the eventual value of the C<MYHOSTNAME> symbol,
6229  which is the name of the host the program is going to run on.
6230  The domain is not kept with hostname, but must be gotten from mydomain.
6231  The dot comes with mydomain, and need not be supplied by the program.
6232  
6233  =item C<myuname>
6234  
6235  From F<Oldconfig.U>:
6236  
6237  The output of C<uname -a> if available, otherwise the hostname. On Xenix,
6238  pseudo variables assignments in the output are stripped, thank you. The
6239  whole thing is then lower-cased.
6240  
6241  =back
6242  
6243  =head2 n
6244  
6245  =over 4
6246  
6247  =item C<n>
6248  
6249  From F<n.U>:
6250  
6251  This variable contains the C<-n> flag if that is what causes the echo
6252  command to suppress newline.  Otherwise it is null.  Correct usage is
6253  $echo $n "prompt for a question: $c".
6254  
6255  =item C<need_va_copy>
6256  
6257  From F<need_va_copy.U>:
6258  
6259  This symbol, if defined, indicates that the system stores
6260  the variable argument list datatype, va_list, in a format
6261  that cannot be copied by simple assignment, so that some
6262  other means must be used when copying is required.
6263  As such systems vary in their provision (or non-provision)
6264  of copying mechanisms, F<handy.h> defines a platform-
6265  C<independent> macro, Perl_va_copy(src, dst), to do the job.
6266  
6267  =item C<netdb_hlen_type>
6268  
6269  From F<netdbtype.U>:
6270  
6271  This variable holds the type used for the 2nd argument to
6272  gethostbyaddr().  Usually, this is int or size_t or unsigned.
6273  This is only useful if you have gethostbyaddr(), naturally.
6274  
6275  =item C<netdb_host_type>
6276  
6277  From F<netdbtype.U>:
6278  
6279  This variable holds the type used for the 1st argument to
6280  gethostbyaddr().  Usually, this is char * or void *,  possibly
6281  with or without a const prefix.
6282  This is only useful if you have gethostbyaddr(), naturally.
6283  
6284  =item C<netdb_name_type>
6285  
6286  From F<netdbtype.U>:
6287  
6288  This variable holds the type used for the argument to
6289  gethostbyname().  Usually, this is char * or const char *.
6290  This is only useful if you have gethostbyname(), naturally.
6291  
6292  =item C<netdb_net_type>
6293  
6294  From F<netdbtype.U>:
6295  
6296  This variable holds the type used for the 1st argument to
6297  getnetbyaddr().  Usually, this is int or long.
6298  This is only useful if you have getnetbyaddr(), naturally.
6299  
6300  =item C<nm>
6301  
6302  From F<Loc.U>:
6303  
6304  This variable is used internally by Configure to determine the
6305  full pathname (if any) of the nm program.  After Configure runs,
6306  the value is reset to a plain C<nm> and is not useful.
6307  
6308  =item C<nm_opt>
6309  
6310  From F<usenm.U>:
6311  
6312  This variable holds the options that may be necessary for nm.
6313  
6314  =item C<nm_so_opt>
6315  
6316  From F<usenm.U>:
6317  
6318  This variable holds the options that may be necessary for nm
6319  to work on a shared library but that can not be used on an
6320  archive library.  Currently, this is only used by Linux, where
6321  nm --dynamic is *required* to get symbols from an C<ELF> library which
6322  has been stripped, but nm --dynamic is *fatal* on an archive library.
6323  Maybe Linux should just always set usenm=false.
6324  
6325  =item C<nonxs_ext>
6326  
6327  From F<Extensions.U>:
6328  
6329  This variable holds a list of all non-xs extensions included
6330  in the package.  All of them will be built.
6331  
6332  =item C<nroff>
6333  
6334  From F<Loc.U>:
6335  
6336  This variable is used internally by Configure to determine the
6337  full pathname (if any) of the nroff program.  After Configure runs,
6338  the value is reset to a plain C<nroff> and is not useful.
6339  
6340  =item C<nv_preserves_uv_bits>
6341  
6342  From F<perlxv.U>:
6343  
6344  This variable indicates how many of bits type uvtype
6345  a variable nvtype can preserve.
6346  
6347  =item C<nveformat>
6348  
6349  From F<perlxvf.U>:
6350  
6351  This variable contains the format string used for printing
6352  a Perl C<NV> using %e-ish floating point format.
6353  
6354  =item C<nvEUformat>
6355  
6356  From F<perlxvf.U>:
6357  
6358  This variable contains the format string used for printing
6359  a Perl C<NV> using %E-ish floating point format.
6360  
6361  =item C<nvfformat>
6362  
6363  From F<perlxvf.U>:
6364  
6365  This variable confains the format string used for printing
6366  a Perl C<NV> using %f-ish floating point format.
6367  
6368  =item C<nvFUformat>
6369  
6370  From F<perlxvf.U>:
6371  
6372  This variable confains the format string used for printing
6373  a Perl C<NV> using %F-ish floating point format.
6374  
6375  =item C<nvgformat>
6376  
6377  From F<perlxvf.U>:
6378  
6379  This variable contains the format string used for printing
6380  a Perl C<NV> using %g-ish floating point format.
6381  
6382  =item C<nvGUformat>
6383  
6384  From F<perlxvf.U>:
6385  
6386  This variable contains the format string used for printing
6387  a Perl C<NV> using %G-ish floating point format.
6388  
6389  =item C<nvsize>
6390  
6391  From F<perlxv.U>:
6392  
6393  This variable is the size of an C<NV> in bytes.
6394  
6395  =item C<nvtype>
6396  
6397  From F<perlxv.U>:
6398  
6399  This variable contains the C type used for Perl's C<NV>.
6400  
6401  =back
6402  
6403  =head2 o
6404  
6405  =over 4
6406  
6407  =item C<o_nonblock>
6408  
6409  From F<nblock_io.U>:
6410  
6411  This variable bears the symbol value to be used during open() or fcntl()
6412  to turn on non-blocking I/O for a file descriptor. If you wish to switch
6413  between blocking and non-blocking, you may try ioctl(C<FIOSNBIO>) instead,
6414  but that is only supported by some devices.
6415  
6416  =item C<obj_ext>
6417  
6418  From F<Unix.U>:
6419  
6420  This is an old synonym for _o.
6421  
6422  =item C<old_pthread_create_joinable>
6423  
6424  From F<d_pthrattrj.U>:
6425  
6426  This variable defines the constant to use for creating joinable
6427  (aka undetached) pthreads.  Unused if F<pthread.h> defines
6428  C<PTHREAD_CREATE_JOINABLE>.  If used, possible values are
6429  C<PTHREAD_CREATE_UNDETACHED> and C<__UNDETACHED>.
6430  
6431  =item C<optimize>
6432  
6433  From F<ccflags.U>:
6434  
6435  This variable contains any F<optimizer/debugger> flag that should be used.
6436  It is up to the Makefile to use it.
6437  
6438  =item C<orderlib>
6439  
6440  From F<orderlib.U>:
6441  
6442  This variable is C<true> if the components of libraries must be ordered
6443  (with `lorder $* | tsort`) before placing them in an archive.  Set to
6444  C<false> if ranlib or ar can generate random libraries.
6445  
6446  =item C<osname>
6447  
6448  From F<Oldconfig.U>:
6449  
6450  This variable contains the operating system name (e.g. sunos,
6451  solaris, hpux, etc.).  It can be useful later on for setting
6452  defaults.  Any spaces are replaced with underscores.  It is set
6453  to a null string if we can't figure it out.
6454  
6455  =item C<osvers>
6456  
6457  From F<Oldconfig.U>:
6458  
6459  This variable contains the operating system version (e.g.
6460  4.1.3, 5.2, etc.).  It is primarily used for helping select
6461  an appropriate hints file, but might be useful elsewhere for
6462  setting defaults.  It is set to '' if we can't figure it out.
6463  We try to be flexible about how much of the version number
6464  to keep, e.g. if 4.1.1, 4.1.2, and 4.1.3 are essentially the
6465  same for this package, hints files might just be F<os_4.0> or
6466  F<os_4.1>, etc., not keeping separate files for each little release.
6467  
6468  =item C<otherlibdirs>
6469  
6470  From F<otherlibdirs.U>:
6471  
6472  This variable contains a colon-separated set of paths for the perl
6473  binary to search for additional library files or modules.
6474  These directories will be tacked to the end of @C<INC>.
6475  Perl will automatically search below each path for version-
6476  and architecture-specific directories.  See inc_version_list
6477  for more details.
6478  A value of C< > means C<none> and is used to preserve this value
6479  for the next run through Configure.
6480  
6481  =back
6482  
6483  =head2 p
6484  
6485  =over 4
6486  
6487  =item C<package>
6488  
6489  From F<package.U>:
6490  
6491  This variable contains the name of the package being constructed.
6492  It is primarily intended for the use of later Configure units.
6493  
6494  =item C<pager>
6495  
6496  From F<pager.U>:
6497  
6498  This variable contains the name of the preferred pager on the system.
6499  Usual values are (the full pathnames of) more, less, pg, or cat.
6500  
6501  =item C<passcat>
6502  
6503  From F<nis.U>:
6504  
6505  This variable contains a command that produces the text of the
6506  F</etc/passwd> file.  This is normally "cat F</etc/passwd>", but can be
6507  "ypcat passwd" when C<NIS> is used.
6508  On some systems, such as os390, there may be no equivalent
6509  command, in which case this variable is unset.
6510  
6511  =item C<patchlevel>
6512  
6513  From F<patchlevel.U>:
6514  
6515  The patchlevel level of this package.
6516  The value of patchlevel comes from the F<patchlevel.h> file.
6517  In a version number such as 5.6.1, this is the C<6>.
6518  In F<patchlevel.h>, this is referred to as C<PERL_VERSION>.
6519  
6520  =item C<path_sep>
6521  
6522  From F<Unix.U>:
6523  
6524  This is an old synonym for p_ in F<Head.U>, the character
6525  used to separate elements in the command shell search C<PATH>.
6526  
6527  =item C<perl>
6528  
6529  From F<Loc.U>:
6530  
6531  This variable is defined but not used by Configure.
6532  The value is a plain '' and is not useful.
6533  
6534  =item C<perl5>
6535  
6536  From F<perl5.U>:
6537  
6538  This variable contains the full path (if any) to a previously
6539  installed F<perl5.005> or later suitable for running the script
6540  to determine inc_version_list.
6541  
6542  =back
6543  
6544  =head2 P
6545  
6546  =over 4
6547  
6548  =item C<PERL_API_REVISION>
6549  
6550  From F<patchlevel.h>:
6551  
6552  This number describes the earliest compatible C<PERL_REVISION> of
6553  Perl (C<compatibility> here being defined as sufficient F<binary/C<API>>
6554  compatibility to run C<XS> code built with the older version).
6555  Normally this does not change across maintenance releases.
6556  Please read the comment in F<patchlevel.h>.
6557  
6558  =item C<PERL_API_SUBVERSION>
6559  
6560  From F<patchlevel.h>:
6561  
6562  This number describes the earliest compatible C<PERL_SUBVERSION> of
6563  Perl (C<compatibility> here being defined as sufficient F<binary/C<API>>
6564  compatibility to run C<XS> code built with the older version).
6565  Normally this does not change across maintenance releases.
6566  Please read the comment in F<patchlevel.h>.
6567  
6568  =item C<PERL_API_VERSION>
6569  
6570  From F<patchlevel.h>:
6571  
6572  This number describes the earliest compatible C<PERL_VERSION> of
6573  Perl (C<compatibility> here being defined as sufficient F<binary/C<API>>
6574  compatibility to run C<XS> code built with the older version).
6575  Normally this does not change across maintenance releases.
6576  Please read the comment in F<patchlevel.h>.
6577  
6578  =item C<PERL_CONFIG_SH>
6579  
6580  From F<Oldsyms.U>:
6581  
6582  This is set to C<true> in F<config.sh> so that a shell script
6583  sourcing F<config.sh> can tell if it has been sourced already.
6584  
6585  =item C<PERL_PATCHLEVEL>
6586  
6587  From F<Oldsyms.U>:
6588  
6589  This symbol reflects the patchlevel, if available. Will usually
6590  come from the F<.patch> file, which is available when the perl
6591  source tree was fetched with rsync.
6592  
6593  =item C<perl_patchlevel>
6594  
6595  From F<patchlevel.U>:
6596  
6597  This is the Perl patch level, a numeric change identifier,
6598  as defined by whichever source code maintenance system
6599  is used to maintain the patches; currently Perforce.
6600  It does not correlate with the Perl version numbers or
6601  the maintenance versus development dichotomy except
6602  by also being increasing.
6603  
6604  =item C<PERL_REVISION>
6605  
6606  From F<Oldsyms.U>:
6607  
6608  In a Perl version number such as 5.6.2, this is the 5.
6609  This value is manually set in F<patchlevel.h>
6610  
6611  =item C<PERL_SUBVERSION>
6612  
6613  From F<Oldsyms.U>:
6614  
6615  In a Perl version number such as 5.6.2, this is the 2.
6616  Values greater than 50 represent potentially unstable
6617  development subversions.
6618  This value is manually set in F<patchlevel.h>
6619  
6620  =item C<PERL_VERSION>
6621  
6622  From F<Oldsyms.U>:
6623  
6624  In a Perl version number such as 5.6.2, this is the 6.
6625  This value is manually set in F<patchlevel.h>
6626  
6627  =item C<perladmin>
6628  
6629  From F<perladmin.U>:
6630  
6631  Electronic mail address of the perl5 administrator.
6632  
6633  =item C<perllibs>
6634  
6635  From F<End.U>:
6636  
6637  The list of libraries needed by Perl only (any libraries needed
6638  by extensions only will by dropped, if using dynamic loading).
6639  
6640  =item C<perlpath>
6641  
6642  From F<perlpath.U>:
6643  
6644  This variable contains the eventual value of the C<PERLPATH> symbol,
6645  which contains the name of the perl interpreter to be used in
6646  shell scripts and in the "eval C<exec>" idiom.  This variable is
6647  not necessarily the pathname of the file containing the perl
6648  interpreter; you must append the executable extension (_exe) if
6649  it is not already present.  Note that Perl code that runs during
6650  the Perl build process cannot reference this variable, as Perl
6651  may not have been installed, or even if installed, may be a
6652  different version of Perl.
6653  
6654  =item C<pg>
6655  
6656  From F<Loc.U>:
6657  
6658  This variable is used internally by Configure to determine the
6659  full pathname (if any) of the pg program.  After Configure runs,
6660  the value is reset to a plain C<pg> and is not useful.
6661  
6662  =item C<phostname>
6663  
6664  From F<myhostname.U>:
6665  
6666  This variable contains the eventual value of the C<PHOSTNAME> symbol,
6667  which is a command that can be fed to popen() to get the host name.
6668  The program should probably not presume that the domain is or isn't
6669  there already.
6670  
6671  =item C<pidtype>
6672  
6673  From F<pidtype.U>:
6674  
6675  This variable defines C<PIDTYPE> to be something like pid_t, int,
6676  ushort, or whatever type is used to declare process ids in the kernel.
6677  
6678  =item C<plibpth>
6679  
6680  From F<libpth.U>:
6681  
6682  Holds the private path used by Configure to find out the libraries.
6683  Its value is prepend to libpth. This variable takes care of special
6684  machines, like the mips.  Usually, it should be empty.
6685  
6686  =item C<pmake>
6687  
6688  From F<Loc.U>:
6689  
6690  This variable is defined but not used by Configure.
6691  The value is a plain '' and is not useful.
6692  
6693  =item C<pr>
6694  
6695  From F<Loc.U>:
6696  
6697  This variable is defined but not used by Configure.
6698  The value is a plain '' and is not useful.
6699  
6700  =item C<prefix>
6701  
6702  From F<prefix.U>:
6703  
6704  This variable holds the name of the directory below which the
6705  user will install the package.  Usually, this is F</usr/local>, and
6706  executables go in F</usr/local/bin>, library stuff in F</usr/local/lib>,
6707  man pages in F</usr/local/man>, etc.  It is only used to set defaults
6708  for things in F<bin.U>, F<mansrc.U>, F<privlib.U>, or F<scriptdir.U>.
6709  
6710  =item C<prefixexp>
6711  
6712  From F<prefix.U>:
6713  
6714  This variable holds the full absolute path of the directory below
6715  which the user will install the package.  Derived from prefix.
6716  
6717  =item C<privlib>
6718  
6719  From F<privlib.U>:
6720  
6721  This variable contains the eventual value of the C<PRIVLIB> symbol,
6722  which is the name of the private library for this package.  It may
6723  have a F<~> on the front. It is up to the makefile to eventually create
6724  this directory while performing installation (with F<~> substitution).
6725  
6726  =item C<privlibexp>
6727  
6728  From F<privlib.U>:
6729  
6730  This variable is the F<~name> expanded version of privlib, so that you
6731  may use it directly in Makefiles or shell scripts.
6732  
6733  =item C<procselfexe>
6734  
6735  From F<d_procselfexe.U>:
6736  
6737  If d_procselfexe is defined, $procselfexe is the filename
6738  of the symbolic link pointing to the absolute pathname of
6739  the executing program.
6740  
6741  =item C<prototype>
6742  
6743  From F<prototype.U>:
6744  
6745  This variable holds the eventual value of C<CAN_PROTOTYPE>, which
6746  indicates the C compiler can handle funciton prototypes.
6747  
6748  =item C<ptrsize>
6749  
6750  From F<ptrsize.U>:
6751  
6752  This variable contains the value of the C<PTRSIZE> symbol, which
6753  indicates to the C program how many bytes there are in a pointer.
6754  
6755  =back
6756  
6757  =head2 q
6758  
6759  =over 4
6760  
6761  =item C<quadkind>
6762  
6763  From F<quadtype.U>:
6764  
6765  This variable, if defined, encodes the type of a quad:
6766  1 = int, 2 = long, 3 = long long, 4 = int64_t.
6767  
6768  =item C<quadtype>
6769  
6770  From F<quadtype.U>:
6771  
6772  This variable defines Quad_t to be something like long, int,
6773  long long, int64_t, or whatever type is used for 64-bit integers.
6774  
6775  =back
6776  
6777  =head2 r
6778  
6779  =over 4
6780  
6781  =item C<randbits>
6782  
6783  From F<randfunc.U>:
6784  
6785  Indicates how many bits are produced by the function used to
6786  generate normalized random numbers.
6787  
6788  =item C<randfunc>
6789  
6790  From F<randfunc.U>:
6791  
6792  Indicates the name of the random number function to use.
6793  Values include drand48, random, and rand. In C programs,
6794  the C<Drand01> macro is defined to generate uniformly distributed
6795  random numbers over the range [0., 1.[ (see drand01 and nrand).
6796  
6797  =item C<random_r_proto>
6798  
6799  From F<d_random_r.U>:
6800  
6801  This variable encodes the prototype of random_r.
6802  It is zero if d_random_r is undef, and one of the
6803  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_random_r
6804  is defined.
6805  
6806  =item C<randseedtype>
6807  
6808  From F<randfunc.U>:
6809  
6810  Indicates the type of the argument of the seedfunc.
6811  
6812  =item C<ranlib>
6813  
6814  From F<orderlib.U>:
6815  
6816  This variable is set to the pathname of the ranlib program, if it is
6817  needed to generate random libraries.  Set to C<:> if ar can generate
6818  random libraries or if random libraries are not supported
6819  
6820  =item C<rd_nodata>
6821  
6822  From F<nblock_io.U>:
6823  
6824  This variable holds the return code from read() when no data is
6825  present. It should be -1, but some systems return 0 when C<O_NDELAY> is
6826  used, which is a shame because you cannot make the difference between
6827  no data and an F<EOF.>. Sigh!
6828  
6829  =item C<readdir64_r_proto>
6830  
6831  From F<d_readdir64_r.U>:
6832  
6833  This variable encodes the prototype of readdir64_r.
6834  It is zero if d_readdir64_r is undef, and one of the
6835  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_readdir64_r
6836  is defined.
6837  
6838  =item C<readdir_r_proto>
6839  
6840  From F<d_readdir_r.U>:
6841  
6842  This variable encodes the prototype of readdir_r.
6843  It is zero if d_readdir_r is undef, and one of the
6844  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_readdir_r
6845  is defined.
6846  
6847  =item C<revision>
6848  
6849  From F<patchlevel.U>:
6850  
6851  The value of revision comes from the F<patchlevel.h> file.
6852  In a version number such as 5.6.1, this is the C<5>.
6853  In F<patchlevel.h>, this is referred to as C<PERL_REVISION>.
6854  
6855  =item C<rm>
6856  
6857  From F<Loc.U>:
6858  
6859  This variable is used internally by Configure to determine the
6860  full pathname (if any) of the rm program.  After Configure runs,
6861  the value is reset to a plain C<rm> and is not useful.
6862  
6863  =item C<rm_try>
6864  
6865  From F<Unix.U>:
6866  
6867  This is a cleanup variable for try test programs.
6868  Internal Configure use only.
6869  
6870  =item C<rmail>
6871  
6872  From F<Loc.U>:
6873  
6874  This variable is defined but not used by Configure.
6875  The value is a plain '' and is not useful.
6876  
6877  =item C<run>
6878  
6879  From F<Cross.U>:
6880  
6881  This variable contains the command used by Configure
6882  to copy and execute a cross-compiled executable in the
6883  target host.  Useful and available only during Perl build.
6884  Empty string '' if not cross-compiling.
6885  
6886  =item C<runnm>
6887  
6888  From F<usenm.U>:
6889  
6890  This variable contains C<true> or C<false> depending whether the
6891  nm extraction should be performed or not, according to the value
6892  of usenm and the flags on the Configure command line.
6893  
6894  =back
6895  
6896  =head2 s
6897  
6898  =over 4
6899  
6900  =item C<sched_yield>
6901  
6902  From F<d_pthread_y.U>:
6903  
6904  This variable defines the way to yield the execution
6905  of the current thread.
6906  
6907  =item C<scriptdir>
6908  
6909  From F<scriptdir.U>:
6910  
6911  This variable holds the name of the directory in which the user wants
6912  to put publicly scripts for the package in question.  It is either
6913  the same directory as for binaries, or a special one that can be
6914  mounted across different architectures, like F</usr/share>. Programs
6915  must be prepared to deal with F<~name> expansion.
6916  
6917  =item C<scriptdirexp>
6918  
6919  From F<scriptdir.U>:
6920  
6921  This variable is the same as scriptdir, but is filename expanded
6922  at configuration time, for programs not wanting to bother with it.
6923  
6924  =item C<sed>
6925  
6926  From F<Loc.U>:
6927  
6928  This variable is used internally by Configure to determine the
6929  full pathname (if any) of the sed program.  After Configure runs,
6930  the value is reset to a plain C<sed> and is not useful.
6931  
6932  =item C<seedfunc>
6933  
6934  From F<randfunc.U>:
6935  
6936  Indicates the random number generating seed function.
6937  Values include srand48, srandom, and srand.
6938  
6939  =item C<selectminbits>
6940  
6941  From F<selectminbits.U>:
6942  
6943  This variable holds the minimum number of bits operated by select.
6944  That is, if you do select(n, ...), how many bits at least will be
6945  cleared in the masks if some activity is detected.  Usually this
6946  is either n or 32*ceil(F<n/32>), especially many little-endians do
6947  the latter.  This is only useful if you have select(), naturally.
6948  
6949  =item C<selecttype>
6950  
6951  From F<selecttype.U>:
6952  
6953  This variable holds the type used for the 2nd, 3rd, and 4th
6954  arguments to select.  Usually, this is C<fd_set *>, if C<HAS_FD_SET>
6955  is defined, and C<int *> otherwise.  This is only useful if you
6956  have select(), naturally.
6957  
6958  =item C<sendmail>
6959  
6960  From F<Loc.U>:
6961  
6962  This variable is defined but not used by Configure.
6963  The value is a plain '' and is not useful.
6964  
6965  =item C<setgrent_r_proto>
6966  
6967  From F<d_setgrent_r.U>:
6968  
6969  This variable encodes the prototype of setgrent_r.
6970  It is zero if d_setgrent_r is undef, and one of the
6971  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_setgrent_r
6972  is defined.
6973  
6974  =item C<sethostent_r_proto>
6975  
6976  From F<d_sethostent_r.U>:
6977  
6978  This variable encodes the prototype of sethostent_r.
6979  It is zero if d_sethostent_r is undef, and one of the
6980  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_sethostent_r
6981  is defined.
6982  
6983  =item C<setlocale_r_proto>
6984  
6985  From F<d_setlocale_r.U>:
6986  
6987  This variable encodes the prototype of setlocale_r.
6988  It is zero if d_setlocale_r is undef, and one of the
6989  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_setlocale_r
6990  is defined.
6991  
6992  =item C<setnetent_r_proto>
6993  
6994  From F<d_setnetent_r.U>:
6995  
6996  This variable encodes the prototype of setnetent_r.
6997  It is zero if d_setnetent_r is undef, and one of the
6998  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_setnetent_r
6999  is defined.
7000  
7001  =item C<setprotoent_r_proto>
7002  
7003  From F<d_setprotoent_r.U>:
7004  
7005  This variable encodes the prototype of setprotoent_r.
7006  It is zero if d_setprotoent_r is undef, and one of the
7007  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_setprotoent_r
7008  is defined.
7009  
7010  =item C<setpwent_r_proto>
7011  
7012  From F<d_setpwent_r.U>:
7013  
7014  This variable encodes the prototype of setpwent_r.
7015  It is zero if d_setpwent_r is undef, and one of the
7016  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_setpwent_r
7017  is defined.
7018  
7019  =item C<setservent_r_proto>
7020  
7021  From F<d_setservent_r.U>:
7022  
7023  This variable encodes the prototype of setservent_r.
7024  It is zero if d_setservent_r is undef, and one of the
7025  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_setservent_r
7026  is defined.
7027  
7028  =item C<sh>
7029  
7030  From F<sh.U>:
7031  
7032  This variable contains the full pathname of the shell used
7033  on this system to execute Bourne shell scripts.  Usually, this will be
7034  F</bin/sh>, though it's possible that some systems will have F</bin/ksh>,
7035  F</bin/pdksh>, F</bin/ash>, F</bin/bash>, or even something such as
7036  D:F</bin/sh.exe>.
7037  This unit comes before F<Options.U>, so you can't set sh with a C<-D>
7038  option, though you can override this (and startsh)
7039  with C<-O -Dsh=F</bin/whatever> -Dstartsh=whatever>
7040  
7041  =item C<shar>
7042  
7043  From F<Loc.U>:
7044  
7045  This variable is defined but not used by Configure.
7046  The value is a plain '' and is not useful.
7047  
7048  =item C<sharpbang>
7049  
7050  From F<spitshell.U>:
7051  
7052  This variable contains the string #! if this system supports that
7053  construct.
7054  
7055  =item C<shmattype>
7056  
7057  From F<d_shmat.U>:
7058  
7059  This symbol contains the type of pointer returned by shmat().
7060  It can be C<void *> or C<char *>.
7061  
7062  =item C<shortsize>
7063  
7064  From F<intsize.U>:
7065  
7066  This variable contains the value of the C<SHORTSIZE> symbol which
7067  indicates to the C program how many bytes there are in a short.
7068  
7069  =item C<shrpenv>
7070  
7071  From F<libperl.U>:
7072  
7073  If the user builds a shared F<libperl.so>, then we need to tell the
7074  C<perl> executable where it will be able to find the installed F<libperl.so>.
7075  One way to do this on some systems is to set the environment variable
7076  C<LD_RUN_PATH> to the directory that will be the final location of the
7077  shared F<libperl.so>.  The makefile can use this with something like
7078  $shrpenv $(C<CC>) -o perl F<perlmain.o> $libperl $libs
7079  Typical values are
7080  shrpenv="env C<LD_RUN_PATH>=F<$archlibexp/C<CORE>>"
7081  or
7082  shrpenv=''
7083  See the main perl F<Makefile.SH> for actual working usage.
7084  Alternatively, we might be able to use a command line option such
7085  as -R F<$archlibexp/C<CORE>> (Solaris) or -Wl,-rpath
7086  F<$archlibexp/C<CORE>> (Linux).
7087  
7088  =item C<shsharp>
7089  
7090  From F<spitshell.U>:
7091  
7092  This variable tells further Configure units whether your sh can
7093  handle # comments.
7094  
7095  =item C<sig_count>
7096  
7097  From F<sig_name.U>:
7098  
7099  This variable holds a number larger than the largest valid
7100  signal number.  This is usually the same as the C<NSIG> macro.
7101  
7102  =item C<sig_name>
7103  
7104  From F<sig_name.U>:
7105  
7106  This variable holds the signal names, space separated. The leading
7107  C<SIG> in signal name is removed.  A C<ZERO> is prepended to the list.
7108  This is currently not used, sig_name_init is used instead.
7109  
7110  =item C<sig_name_init>
7111  
7112  From F<sig_name.U>:
7113  
7114  This variable holds the signal names, enclosed in double quotes and
7115  separated by commas, suitable for use in the C<SIG_NAME> definition
7116  below.  A C<ZERO> is prepended to the list, and the list is
7117  terminated with a plain 0.  The leading C<SIG> in signal names
7118  is removed. See sig_num.
7119  
7120  =item C<sig_num>
7121  
7122  From F<sig_name.U>:
7123  
7124  This variable holds the signal numbers, space separated. A C<ZERO> is
7125  prepended to the list (corresponding to the fake C<SIGZERO>).
7126  Those numbers correspond to  the value of the signal listed
7127  in the same place within the sig_name list.
7128  This is currently not used, sig_num_init is used instead.
7129  
7130  =item C<sig_num_init>
7131  
7132  From F<sig_name.U>:
7133  
7134  This variable holds the signal numbers, enclosed in double quotes and
7135  separated by commas, suitable for use in the C<SIG_NUM> definition
7136  below.  A C<ZERO> is prepended to the list, and the list is
7137  terminated with a plain 0.
7138  
7139  =item C<sig_size>
7140  
7141  From F<sig_name.U>:
7142  
7143  This variable contains the number of elements of the sig_name
7144  and sig_num arrays.
7145  
7146  =item C<signal_t>
7147  
7148  From F<d_voidsig.U>:
7149  
7150  This variable holds the type of the signal handler (void or int).
7151  
7152  =item C<sitearch>
7153  
7154  From F<sitearch.U>:
7155  
7156  This variable contains the eventual value of the C<SITEARCH> symbol,
7157  which is the name of the private library for this package.  It may
7158  have a F<~> on the front. It is up to the makefile to eventually create
7159  this directory while performing installation (with F<~> substitution).
7160  The standard distribution will put nothing in this directory.
7161  After perl has been installed, users may install their own local
7162  architecture-dependent modules in this directory with
7163  MakeMaker F<Makefile.PL>
7164  or equivalent.  See C<INSTALL> for details.
7165  
7166  =item C<sitearchexp>
7167  
7168  From F<sitearch.U>:
7169  
7170  This variable is the F<~name> expanded version of sitearch, so that you
7171  may use it directly in Makefiles or shell scripts.
7172  
7173  =item C<sitebin>
7174  
7175  From F<sitebin.U>:
7176  
7177  This variable holds the name of the directory in which the user wants
7178  to put add-on publicly executable files for the package in question.  It
7179  is most often a local directory such as F</usr/local/bin>. Programs using
7180  this variable must be prepared to deal with F<~name> substitution.
7181  The standard distribution will put nothing in this directory.
7182  After perl has been installed, users may install their own local
7183  executables in this directory with
7184  MakeMaker F<Makefile.PL>
7185  or equivalent.  See C<INSTALL> for details.
7186  
7187  =item C<sitebinexp>
7188  
7189  From F<sitebin.U>:
7190  
7191  This is the same as the sitebin variable, but is filename expanded at
7192  configuration time, for use in your makefiles.
7193  
7194  =item C<sitehtml1dir>
7195  
7196  From F<sitehtml1dir.U>:
7197  
7198  This variable contains the name of the directory in which site-specific
7199  html source pages are to be put.  It is the responsibility of the
7200  F<Makefile.SH> to get the value of this into the proper command.
7201  You must be prepared to do the F<~name> expansion yourself.
7202  The standard distribution will put nothing in this directory.
7203  After perl has been installed, users may install their own local
7204  html pages in this directory with
7205  MakeMaker F<Makefile.PL>
7206  or equivalent.  See C<INSTALL> for details.
7207  
7208  =item C<sitehtml1direxp>
7209  
7210  From F<sitehtml1dir.U>:
7211  
7212  This variable is the same as the sitehtml1dir variable, but is filename
7213  expanded at configuration time, for convenient use in makefiles.
7214  
7215  =item C<sitehtml3dir>
7216  
7217  From F<sitehtml3dir.U>:
7218  
7219  This variable contains the name of the directory in which site-specific
7220  library html source pages are to be put.  It is the responsibility of the
7221  F<Makefile.SH> to get the value of this into the proper command.
7222  You must be prepared to do the F<~name> expansion yourself.
7223  The standard distribution will put nothing in this directory.
7224  After perl has been installed, users may install their own local
7225  library html pages in this directory with
7226  MakeMaker F<Makefile.PL>
7227  or equivalent.  See C<INSTALL> for details.
7228  
7229  =item C<sitehtml3direxp>
7230  
7231  From F<sitehtml3dir.U>:
7232  
7233  This variable is the same as the sitehtml3dir variable, but is filename
7234  expanded at configuration time, for convenient use in makefiles.
7235  
7236  =item C<sitelib>
7237  
7238  From F<sitelib.U>:
7239  
7240  This variable contains the eventual value of the C<SITELIB> symbol,
7241  which is the name of the private library for this package.  It may
7242  have a F<~> on the front. It is up to the makefile to eventually create
7243  this directory while performing installation (with F<~> substitution).
7244  The standard distribution will put nothing in this directory.
7245  After perl has been installed, users may install their own local
7246  architecture-independent modules in this directory with
7247  MakeMaker F<Makefile.PL>
7248  or equivalent.  See C<INSTALL> for details.
7249  
7250  =item C<sitelib_stem>
7251  
7252  From F<sitelib.U>:
7253  
7254  This variable is $sitelibexp with any trailing version-specific component
7255  removed.  The elements in inc_version_list (F<inc_version_list.U>) can
7256  be tacked onto this variable to generate a list of directories to search.
7257  
7258  =item C<sitelibexp>
7259  
7260  From F<sitelib.U>:
7261  
7262  This variable is the F<~name> expanded version of sitelib, so that you
7263  may use it directly in Makefiles or shell scripts.
7264  
7265  =item C<siteman1dir>
7266  
7267  From F<siteman1dir.U>:
7268  
7269  This variable contains the name of the directory in which site-specific
7270  manual source pages are to be put.  It is the responsibility of the
7271  F<Makefile.SH> to get the value of this into the proper command.
7272  You must be prepared to do the F<~name> expansion yourself.
7273  The standard distribution will put nothing in this directory.
7274  After perl has been installed, users may install their own local
7275  man1 pages in this directory with
7276  MakeMaker F<Makefile.PL>
7277  or equivalent.  See C<INSTALL> for details.
7278  
7279  =item C<siteman1direxp>
7280  
7281  From F<siteman1dir.U>:
7282  
7283  This variable is the same as the siteman1dir variable, but is filename
7284  expanded at configuration time, for convenient use in makefiles.
7285  
7286  =item C<siteman3dir>
7287  
7288  From F<siteman3dir.U>:
7289  
7290  This variable contains the name of the directory in which site-specific
7291  library man source pages are to be put.  It is the responsibility of the
7292  F<Makefile.SH> to get the value of this into the proper command.
7293  You must be prepared to do the F<~name> expansion yourself.
7294  The standard distribution will put nothing in this directory.
7295  After perl has been installed, users may install their own local
7296  man3 pages in this directory with
7297  MakeMaker F<Makefile.PL>
7298  or equivalent.  See C<INSTALL> for details.
7299  
7300  =item C<siteman3direxp>
7301  
7302  From F<siteman3dir.U>:
7303  
7304  This variable is the same as the siteman3dir variable, but is filename
7305  expanded at configuration time, for convenient use in makefiles.
7306  
7307  =item C<siteprefix>
7308  
7309  From F<siteprefix.U>:
7310  
7311  This variable holds the full absolute path of the directory below
7312  which the user will install add-on packages.
7313  See C<INSTALL> for usage and examples.
7314  
7315  =item C<siteprefixexp>
7316  
7317  From F<siteprefix.U>:
7318  
7319  This variable holds the full absolute path of the directory below
7320  which the user will install add-on packages.  Derived from siteprefix.
7321  
7322  =item C<sitescript>
7323  
7324  From F<sitescript.U>:
7325  
7326  This variable holds the name of the directory in which the user wants
7327  to put add-on publicly executable files for the package in question.  It
7328  is most often a local directory such as F</usr/local/bin>. Programs using
7329  this variable must be prepared to deal with F<~name> substitution.
7330  The standard distribution will put nothing in this directory.
7331  After perl has been installed, users may install their own local
7332  scripts in this directory with
7333  MakeMaker F<Makefile.PL>
7334  or equivalent.  See C<INSTALL> for details.
7335  
7336  =item C<sitescriptexp>
7337  
7338  From F<sitescript.U>:
7339  
7340  This is the same as the sitescript variable, but is filename expanded at
7341  configuration time, for use in your makefiles.
7342  
7343  =item C<sizesize>
7344  
7345  From F<sizesize.U>:
7346  
7347  This variable contains the size of a sizetype in bytes.
7348  
7349  =item C<sizetype>
7350  
7351  From F<sizetype.U>:
7352  
7353  This variable defines sizetype to be something like size_t,
7354  unsigned long, or whatever type is used to declare length
7355  parameters for string functions.
7356  
7357  =item C<sleep>
7358  
7359  From F<Loc.U>:
7360  
7361  This variable is defined but not used by Configure.
7362  The value is a plain '' and is not useful.
7363  
7364  =item C<smail>
7365  
7366  From F<Loc.U>:
7367  
7368  This variable is defined but not used by Configure.
7369  The value is a plain '' and is not useful.
7370  
7371  =item C<so>
7372  
7373  From F<so.U>:
7374  
7375  This variable holds the extension used to identify shared libraries
7376  (also known as shared objects) on the system. Usually set to C<so>.
7377  
7378  =item C<sockethdr>
7379  
7380  From F<d_socket.U>:
7381  
7382  This variable has any cpp C<-I> flags needed for socket support.
7383  
7384  =item C<socketlib>
7385  
7386  From F<d_socket.U>:
7387  
7388  This variable has the names of any libraries needed for socket support.
7389  
7390  =item C<socksizetype>
7391  
7392  From F<socksizetype.U>:
7393  
7394  This variable holds the type used for the size argument
7395  for various socket calls like accept.  Usual values include
7396  socklen_t, size_t, and int.
7397  
7398  =item C<sort>
7399  
7400  From F<Loc.U>:
7401  
7402  This variable is used internally by Configure to determine the
7403  full pathname (if any) of the sort program.  After Configure runs,
7404  the value is reset to a plain C<sort> and is not useful.
7405  
7406  =item C<spackage>
7407  
7408  From F<package.U>:
7409  
7410  This variable contains the name of the package being constructed,
7411  with the first letter uppercased, F<i.e>. suitable for starting
7412  sentences.
7413  
7414  =item C<spitshell>
7415  
7416  From F<spitshell.U>:
7417  
7418  This variable contains the command necessary to spit out a runnable
7419  shell on this system.  It is either cat or a grep C<-v> for # comments.
7420  
7421  =item C<sPRId64>
7422  
7423  From F<quadfio.U>:
7424  
7425  This variable, if defined, contains the string used by stdio to
7426  format 64-bit decimal numbers (format C<d>) for output.
7427  
7428  =item C<sPRIeldbl>
7429  
7430  From F<longdblfio.U>:
7431  
7432  This variable, if defined, contains the string used by stdio to
7433  format long doubles (format C<e>) for output.
7434  
7435  =item C<sPRIEUldbl>
7436  
7437  From F<longdblfio.U>:
7438  
7439  This variable, if defined, contains the string used by stdio to
7440  format long doubles (format C<E>) for output.
7441  The C<U> in the name is to separate this from sPRIeldbl so that even
7442  case-blind systems can see the difference.
7443  
7444  =item C<sPRIfldbl>
7445  
7446  From F<longdblfio.U>:
7447  
7448  This variable, if defined, contains the string used by stdio to
7449  format long doubles (format C<f>) for output.
7450  
7451  =item C<sPRIFUldbl>
7452  
7453  From F<longdblfio.U>:
7454  
7455  This variable, if defined, contains the string used by stdio to
7456  format long doubles (format C<F>) for output.
7457  The C<U> in the name is to separate this from sPRIfldbl so that even
7458  case-blind systems can see the difference.
7459  
7460  =item C<sPRIgldbl>
7461  
7462  From F<longdblfio.U>:
7463  
7464  This variable, if defined, contains the string used by stdio to
7465  format long doubles (format C<g>) for output.
7466  
7467  =item C<sPRIGUldbl>
7468  
7469  From F<longdblfio.U>:
7470  
7471  This variable, if defined, contains the string used by stdio to
7472  format long doubles (format C<G>) for output.
7473  The C<U> in the name is to separate this from sPRIgldbl so that even
7474  case-blind systems can see the difference.
7475  
7476  =item C<sPRIi64>
7477  
7478  From F<quadfio.U>:
7479  
7480  This variable, if defined, contains the string used by stdio to
7481  format 64-bit decimal numbers (format C<i>) for output.
7482  
7483  =item C<sPRIo64>
7484  
7485  From F<quadfio.U>:
7486  
7487  This variable, if defined, contains the string used by stdio to
7488  format 64-bit octal numbers (format C<o>) for output.
7489  
7490  =item C<sPRIu64>
7491  
7492  From F<quadfio.U>:
7493  
7494  This variable, if defined, contains the string used by stdio to
7495  format 64-bit unsigned decimal numbers (format C<u>) for output.
7496  
7497  =item C<sPRIx64>
7498  
7499  From F<quadfio.U>:
7500  
7501  This variable, if defined, contains the string used by stdio to
7502  format 64-bit hexadecimal numbers (format C<x>) for output.
7503  
7504  =item C<sPRIXU64>
7505  
7506  From F<quadfio.U>:
7507  
7508  This variable, if defined, contains the string used by stdio to
7509  format 64-bit hExADECimAl numbers (format C<X>) for output.
7510  The C<U> in the name is to separate this from sPRIx64 so that even
7511  case-blind systems can see the difference.
7512  
7513  =item C<srand48_r_proto>
7514  
7515  From F<d_srand48_r.U>:
7516  
7517  This variable encodes the prototype of srand48_r.
7518  It is zero if d_srand48_r is undef, and one of the
7519  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_srand48_r
7520  is defined.
7521  
7522  =item C<srandom_r_proto>
7523  
7524  From F<d_srandom_r.U>:
7525  
7526  This variable encodes the prototype of srandom_r.
7527  It is zero if d_srandom_r is undef, and one of the
7528  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_srandom_r
7529  is defined.
7530  
7531  =item C<src>
7532  
7533  From F<src.U>:
7534  
7535  This variable holds the path to the package source. It is up to
7536  the Makefile to use this variable and set C<VPATH> accordingly to
7537  find the sources remotely.
7538  
7539  =item C<sSCNfldbl>
7540  
7541  From F<longdblfio.U>:
7542  
7543  This variable, if defined, contains the string used by stdio to
7544  format long doubles (format C<f>) for input.
7545  
7546  =item C<ssizetype>
7547  
7548  From F<ssizetype.U>:
7549  
7550  This variable defines ssizetype to be something like ssize_t,
7551  long or int.  It is used by functions that return a count
7552  of bytes or an error condition.  It must be a signed type.
7553  We will pick a type such that sizeof(SSize_t) == sizeof(Size_t).
7554  
7555  =item C<startperl>
7556  
7557  From F<startperl.U>:
7558  
7559  This variable contains the string to put on the front of a perl
7560  script to make sure (hopefully) that it runs with perl and not some
7561  shell. Of course, that leading line must be followed by the classical
7562  perl idiom:
7563  eval 'exec perl -S $0 $1+C<$@>}'
7564  if $running_under_some_shell;
7565  to guarantee perl startup should the shell execute the script. Note
7566  that this magic incatation is not understood by csh.
7567  
7568  =item C<startsh>
7569  
7570  From F<startsh.U>:
7571  
7572  This variable contains the string to put on the front of a shell
7573  script to make sure (hopefully) that it runs with sh and not some
7574  other shell.
7575  
7576  =item C<static_ext>
7577  
7578  From F<Extensions.U>:
7579  
7580  This variable holds a list of C<XS> extension files we want to
7581  link statically into the package.  It is used by Makefile.
7582  
7583  =item C<stdchar>
7584  
7585  From F<stdchar.U>:
7586  
7587  This variable conditionally defines C<STDCHAR> to be the type of char
7588  used in F<stdio.h>.  It has the values "unsigned char" or C<char>.
7589  
7590  =item C<stdio_base>
7591  
7592  From F<d_stdstdio.U>:
7593  
7594  This variable defines how, given a C<FILE> pointer, fp, to access the
7595  _base field (or equivalent) of F<stdio.h>'s C<FILE> structure.  This will
7596  be used to define the macro FILE_base(fp).
7597  
7598  =item C<stdio_bufsiz>
7599  
7600  From F<d_stdstdio.U>:
7601  
7602  This variable defines how, given a C<FILE> pointer, fp, to determine
7603  the number of bytes store in the I/O buffer pointer to by the
7604  _base field (or equivalent) of F<stdio.h>'s C<FILE> structure.  This will
7605  be used to define the macro FILE_bufsiz(fp).
7606  
7607  =item C<stdio_cnt>
7608  
7609  From F<d_stdstdio.U>:
7610  
7611  This variable defines how, given a C<FILE> pointer, fp, to access the
7612  _cnt field (or equivalent) of F<stdio.h>'s C<FILE> structure.  This will
7613  be used to define the macro FILE_cnt(fp).
7614  
7615  =item C<stdio_filbuf>
7616  
7617  From F<d_stdstdio.U>:
7618  
7619  This variable defines how, given a C<FILE> pointer, fp, to tell
7620  stdio to refill its internal buffers (?).  This will
7621  be used to define the macro FILE_filbuf(fp).
7622  
7623  =item C<stdio_ptr>
7624  
7625  From F<d_stdstdio.U>:
7626  
7627  This variable defines how, given a C<FILE> pointer, fp, to access the
7628  _ptr field (or equivalent) of F<stdio.h>'s C<FILE> structure.  This will
7629  be used to define the macro FILE_ptr(fp).
7630  
7631  =item C<stdio_stream_array>
7632  
7633  From F<stdio_streams.U>:
7634  
7635  This variable tells the name of the array holding the stdio streams.
7636  Usual values include _iob, __iob, and __sF.
7637  
7638  =item C<strerror_r_proto>
7639  
7640  From F<d_strerror_r.U>:
7641  
7642  This variable encodes the prototype of strerror_r.
7643  It is zero if d_strerror_r is undef, and one of the
7644  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_strerror_r
7645  is defined.
7646  
7647  =item C<strings>
7648  
7649  From F<i_string.U>:
7650  
7651  This variable holds the full path of the string header that will be
7652  used. Typically F</usr/include/string.h> or F</usr/include/strings.h>.
7653  
7654  =item C<submit>
7655  
7656  From F<Loc.U>:
7657  
7658  This variable is defined but not used by Configure.
7659  The value is a plain '' and is not useful.
7660  
7661  =item C<subversion>
7662  
7663  From F<patchlevel.U>:
7664  
7665  The subversion level of this package.
7666  The value of subversion comes from the F<patchlevel.h> file.
7667  In a version number such as 5.6.1, this is the C<1>.
7668  In F<patchlevel.h>, this is referred to as C<PERL_SUBVERSION>.
7669  This is unique to perl.
7670  
7671  =item C<sysman>
7672  
7673  From F<sysman.U>:
7674  
7675  This variable holds the place where the manual is located on this
7676  system. It is not the place where the user wants to put his manual
7677  pages. Rather it is the place where Configure may look to find manual
7678  for unix commands (section 1 of the manual usually). See mansrc.
7679  
7680  =back
7681  
7682  =head2 t
7683  
7684  =over 4
7685  
7686  =item C<tail>
7687  
7688  From F<Loc.U>:
7689  
7690  This variable is defined but not used by Configure.
7691  The value is a plain '' and is not useful.
7692  
7693  =item C<tar>
7694  
7695  From F<Loc.U>:
7696  
7697  This variable is defined but not used by Configure.
7698  The value is a plain '' and is not useful.
7699  
7700  =item C<targetarch>
7701  
7702  From F<Cross.U>:
7703  
7704  If cross-compiling, this variable contains the target architecture.
7705  If not, this will be empty.
7706  
7707  =item C<tbl>
7708  
7709  From F<Loc.U>:
7710  
7711  This variable is defined but not used by Configure.
7712  The value is a plain '' and is not useful.
7713  
7714  =item C<tee>
7715  
7716  From F<Loc.U>:
7717  
7718  This variable is defined but not used by Configure.
7719  The value is a plain '' and is not useful.
7720  
7721  =item C<test>
7722  
7723  From F<Loc.U>:
7724  
7725  This variable is used internally by Configure to determine the
7726  full pathname (if any) of the test program.  After Configure runs,
7727  the value is reset to a plain C<test> and is not useful.
7728  
7729  =item C<timeincl>
7730  
7731  From F<i_time.U>:
7732  
7733  This variable holds the full path of the included time header(s).
7734  
7735  =item C<timetype>
7736  
7737  From F<d_time.U>:
7738  
7739  This variable holds the type returned by time(). It can be long,
7740  or time_t on C<BSD> sites (in which case <sys/types.h> should be
7741  included). Anyway, the type Time_t should be used.
7742  
7743  =item C<tmpnam_r_proto>
7744  
7745  From F<d_tmpnam_r.U>:
7746  
7747  This variable encodes the prototype of tmpnam_r.
7748  It is zero if d_tmpnam_r is undef, and one of the
7749  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_tmpnam_r
7750  is defined.
7751  
7752  =item C<to>
7753  
7754  From F<Cross.U>:
7755  
7756  This variable contains the command used by Configure
7757  to copy to from the target host.  Useful and available
7758  only during Perl build.
7759  The string C<:> if not cross-compiling.
7760  
7761  =item C<touch>
7762  
7763  From F<Loc.U>:
7764  
7765  This variable is used internally by Configure to determine the
7766  full pathname (if any) of the touch program.  After Configure runs,
7767  the value is reset to a plain C<touch> and is not useful.
7768  
7769  =item C<tr>
7770  
7771  From F<Loc.U>:
7772  
7773  This variable is used internally by Configure to determine the
7774  full pathname (if any) of the tr program.  After Configure runs,
7775  the value is reset to a plain C<tr> and is not useful.
7776  
7777  =item C<trnl>
7778  
7779  From F<trnl.U>:
7780  
7781  This variable contains the value to be passed to the tr(1)
7782  command to transliterate a newline.  Typical values are
7783  C<\012> and C<\n>.  This is needed for C<EBCDIC> systems where
7784  newline is not necessarily C<\012>.
7785  
7786  =item C<troff>
7787  
7788  From F<Loc.U>:
7789  
7790  This variable is defined but not used by Configure.
7791  The value is a plain '' and is not useful.
7792  
7793  =item C<ttyname_r_proto>
7794  
7795  From F<d_ttyname_r.U>:
7796  
7797  This variable encodes the prototype of ttyname_r.
7798  It is zero if d_ttyname_r is undef, and one of the
7799  C<REENTRANT_PROTO_T_ABC> macros of F<reentr.h> if d_ttyname_r
7800  is defined.
7801  
7802  =back
7803  
7804  =head2 u
7805  
7806  =over 4
7807  
7808  =item C<u16size>
7809  
7810  From F<perlxv.U>:
7811  
7812  This variable is the size of an U16 in bytes.
7813  
7814  =item C<u16type>
7815  
7816  From F<perlxv.U>:
7817  
7818  This variable contains the C type used for Perl's U16.
7819  
7820  =item C<u32size>
7821  
7822  From F<perlxv.U>:
7823  
7824  This variable is the size of an U32 in bytes.
7825  
7826  =item C<u32type>
7827  
7828  From F<perlxv.U>:
7829  
7830  This variable contains the C type used for Perl's U32.
7831  
7832  =item C<u64size>
7833  
7834  From F<perlxv.U>:
7835  
7836  This variable is the size of an U64 in bytes.
7837  
7838  =item C<u64type>
7839  
7840  From F<perlxv.U>:
7841  
7842  This variable contains the C type used for Perl's U64.
7843  
7844  =item C<u8size>
7845  
7846  From F<perlxv.U>:
7847  
7848  This variable is the size of an U8 in bytes.
7849  
7850  =item C<u8type>
7851  
7852  From F<perlxv.U>:
7853  
7854  This variable contains the C type used for Perl's U8.
7855  
7856  =item C<uidformat>
7857  
7858  From F<uidf.U>:
7859  
7860  This variable contains the format string used for printing a Uid_t.
7861  
7862  =item C<uidsign>
7863  
7864  From F<uidsign.U>:
7865  
7866  This variable contains the signedness of a uidtype.
7867  1 for unsigned, -1 for signed.
7868  
7869  =item C<uidsize>
7870  
7871  From F<uidsize.U>:
7872  
7873  This variable contains the size of a uidtype in bytes.
7874  
7875  =item C<uidtype>
7876  
7877  From F<uidtype.U>:
7878  
7879  This variable defines Uid_t to be something like uid_t, int,
7880  ushort, or whatever type is used to declare user ids in the kernel.
7881  
7882  =item C<uname>
7883  
7884  From F<Loc.U>:
7885  
7886  This variable is used internally by Configure to determine the
7887  full pathname (if any) of the uname program.  After Configure runs,
7888  the value is reset to a plain C<uname> and is not useful.
7889  
7890  =item C<uniq>
7891  
7892  From F<Loc.U>:
7893  
7894  This variable is used internally by Configure to determine the
7895  full pathname (if any) of the uniq program.  After Configure runs,
7896  the value is reset to a plain C<uniq> and is not useful.
7897  
7898  =item C<uquadtype>
7899  
7900  From F<quadtype.U>:
7901  
7902  This variable defines Uquad_t to be something like unsigned long,
7903  unsigned int, unsigned long long, uint64_t, or whatever type is
7904  used for 64-bit integers.
7905  
7906  =item C<use5005threads>
7907  
7908  From F<usethreads.U>:
7909  
7910  This variable conditionally defines the USE_5005THREADS symbol,
7911  and indicates that Perl should be built to use the 5.005-based
7912  threading implementation. Only valid up to 5.8.x.
7913  
7914  =item C<use64bitall>
7915  
7916  From F<use64bits.U>:
7917  
7918  This variable conditionally defines the USE_64_BIT_ALL symbol,
7919  and indicates that 64-bit integer types should be used
7920  when available.  The maximal possible
7921  64-bitness is employed: LP64 or ILP64, meaning that you will
7922  be able to use more than 2 gigabytes of memory.  This mode is
7923  even more binary incompatible than USE_64_BIT_INT. You may not
7924  be able to run the resulting executable in a 32-bit C<CPU> at all or
7925  you may need at least to reboot your C<OS> to 64-bit mode.
7926  
7927  =item C<use64bitint>
7928  
7929  From F<use64bits.U>:
7930  
7931  This variable conditionally defines the USE_64_BIT_INT symbol,
7932  and indicates that 64-bit integer types should be used
7933  when available.  The minimal possible 64-bitness
7934  is employed, just enough to get 64-bit integers into Perl.
7935  This may mean using for example "long longs", while your memory
7936  may still be limited to 2 gigabytes.
7937  
7938  =item C<usecrosscompile>
7939  
7940  From F<Cross.U>:
7941  
7942  This variable conditionally defines the C<USE_CROSS_COMPILE> symbol,
7943  and indicates that Perl has been cross-compiled.
7944  
7945  =item C<usedl>
7946  
7947  From F<dlsrc.U>:
7948  
7949  This variable indicates if the system supports dynamic
7950  loading of some sort.  See also dlsrc and dlobj.
7951  
7952  =item C<usefaststdio>
7953  
7954  From F<usefaststdio.U>:
7955  
7956  This variable conditionally defines the C<USE_FAST_STDIO> symbol,
7957  and indicates that Perl should be built to use C<fast stdio>.
7958  Defaults to define in Perls 5.8 and earlier, to undef later.
7959  
7960  =item C<useithreads>
7961  
7962  From F<usethreads.U>:
7963  
7964  This variable conditionally defines the C<USE_ITHREADS> symbol,
7965  and indicates that Perl should be built to use the interpreter-based
7966  threading implementation.
7967  
7968  =item C<uselargefiles>
7969  
7970  From F<uselfs.U>:
7971  
7972  This variable conditionally defines the C<USE_LARGE_FILES> symbol,
7973  and indicates that large file interfaces should be used when
7974  available.
7975  
7976  =item C<uselongdouble>
7977  
7978  From F<uselongdbl.U>:
7979  
7980  This variable conditionally defines the C<USE_LONG_DOUBLE> symbol,
7981  and indicates that long doubles should be used when available.
7982  
7983  =item C<usemallocwrap>
7984  
7985  From F<mallocsrc.U>:
7986  
7987  This variable contains y if we are wrapping malloc to prevent
7988  integer overflow during size calculations.
7989  
7990  =item C<usemorebits>
7991  
7992  From F<usemorebits.U>:
7993  
7994  This variable conditionally defines the C<USE_MORE_BITS> symbol,
7995  and indicates that explicit 64-bit interfaces and long doubles
7996  should be used when available.
7997  
7998  =item C<usemultiplicity>
7999  
8000  From F<usemultiplicity.U>:
8001  
8002  This variable conditionally defines the C<MULTIPLICITY> symbol,
8003  and indicates that Perl should be built to use multiplicity.
8004  
8005  =item C<usemymalloc>
8006  
8007  From F<mallocsrc.U>:
8008  
8009  This variable contains y if the malloc that comes with this package
8010  is desired over the system's version of malloc.  People often include
8011  special versions of malloc for effiency, but such versions are often
8012  less portable.  See also mallocsrc and mallocobj.
8013  If this is C<y>, then -lmalloc is removed from $libs.
8014  
8015  =item C<usenm>
8016  
8017  From F<usenm.U>:
8018  
8019  This variable contains C<true> or C<false> depending whether the
8020  nm extraction is wanted or not.
8021  
8022  =item C<useopcode>
8023  
8024  From F<Extensions.U>:
8025  
8026  This variable holds either C<true> or C<false> to indicate
8027  whether the Opcode extension should be used.  The sole
8028  use for this currently is to allow an easy mechanism
8029  for users to skip the Opcode extension from the Configure
8030  command line.
8031  
8032  =item C<useperlio>
8033  
8034  From F<useperlio.U>:
8035  
8036  This variable conditionally defines the C<USE_PERLIO> symbol,
8037  and indicates that the PerlIO abstraction should be
8038  used throughout.
8039  
8040  =item C<useposix>
8041  
8042  From F<Extensions.U>:
8043  
8044  This variable holds either C<true> or C<false> to indicate
8045  whether the C<POSIX> extension should be used.  The sole
8046  use for this currently is to allow an easy mechanism
8047  for hints files to indicate that C<POSIX> will not compile
8048  on a particular system.
8049  
8050  =item C<usereentrant>
8051  
8052  From F<usethreads.U>:
8053  
8054  This variable conditionally defines the C<USE_REENTRANT_API> symbol,
8055  which indicates that the thread code may try to use the various
8056  _r versions of library functions.  This is only potentially
8057  meaningful if usethreads is set and is very experimental, it is
8058  not even prompted for.
8059  
8060  =item C<userelocatableinc>
8061  
8062  From F<bin.U>:
8063  
8064  This variable is set to true to indicate that perl should relocate
8065  @C<INC> entries at runtime based on the path to the perl binary.
8066  Any @C<INC> paths starting F<.../> are relocated relative to the directory
8067  containing the perl binary, and a logical cleanup of the path is then
8068  made around the join point (removing F<dir/../> pairs)
8069  
8070  =item C<usesfio>
8071  
8072  From F<d_sfio.U>:
8073  
8074  This variable is set to true when the user agrees to use sfio.
8075  It is set to false when sfio is not available or when the user
8076  explicitely requests not to use sfio.  It is here primarily so
8077  that command-line settings can override the auto-detection of
8078  d_sfio without running into a "WHOA THERE".
8079  
8080  =item C<useshrplib>
8081  
8082  From F<libperl.U>:
8083  
8084  This variable is set to C<true> if the user wishes
8085  to build a shared libperl, and C<false> otherwise.
8086  
8087  =item C<usesitecustomize>
8088  
8089  From F<d_sitecustomize.U>:
8090  
8091  This variable is set to true when the user requires a mechanism that
8092  allows the sysadmin to add entries to @C<INC> at runtime.  This variable
8093  being set, makes perl run F<$F<sitelib/sitecustomize.pl>> at startup.
8094  
8095  =item C<usesocks>
8096  
8097  From F<usesocks.U>:
8098  
8099  This variable conditionally defines the C<USE_SOCKS> symbol,
8100  and indicates that Perl should be built to use C<SOCKS>.
8101  
8102  =item C<usethreads>
8103  
8104  From F<usethreads.U>:
8105  
8106  This variable conditionally defines the C<USE_THREADS> symbol,
8107  and indicates that Perl should be built to use threads.
8108  
8109  =item C<usevendorprefix>
8110  
8111  From F<vendorprefix.U>:
8112  
8113  This variable tells whether the vendorprefix
8114  and consequently other vendor* paths are in use.
8115  
8116  =item C<usevfork>
8117  
8118  From F<d_vfork.U>:
8119  
8120  This variable is set to true when the user accepts to use vfork.
8121  It is set to false when no vfork is available or when the user
8122  explicitely requests not to use vfork.
8123  
8124  =item C<usrinc>
8125  
8126  From F<usrinc.U>:
8127  
8128  This variable holds the path of the include files, which is
8129  usually F</usr/include>. It is mainly used by other Configure units.
8130  
8131  =item C<uuname>
8132  
8133  From F<Loc.U>:
8134  
8135  This variable is defined but not used by Configure.
8136  The value is a plain '' and is not useful.
8137  
8138  =item C<uvoformat>
8139  
8140  From F<perlxvf.U>:
8141  
8142  This variable contains the format string used for printing
8143  a Perl C<UV> as an unsigned octal integer.
8144  
8145  =item C<uvsize>
8146  
8147  From F<perlxv.U>:
8148  
8149  This variable is the size of a C<UV> in bytes.
8150  
8151  =item C<uvtype>
8152  
8153  From F<perlxv.U>:
8154  
8155  This variable contains the C type used for Perl's C<UV>.
8156  
8157  =item C<uvuformat>
8158  
8159  From F<perlxvf.U>:
8160  
8161  This variable contains the format string used for printing
8162  a Perl C<UV> as an unsigned decimal integer.
8163  
8164  =item C<uvxformat>
8165  
8166  From F<perlxvf.U>:
8167  
8168  This variable contains the format string used for printing
8169  a Perl C<UV> as an unsigned hexadecimal integer in lowercase abcdef.
8170  
8171  =item C<uvXUformat>
8172  
8173  From F<perlxvf.U>:
8174  
8175  This variable contains the format string used for printing
8176  a Perl C<UV> as an unsigned hexadecimal integer in uppercase C<ABCDEF>.
8177  
8178  =back
8179  
8180  =head2 v
8181  
8182  =over 4
8183  
8184  =item C<vendorarch>
8185  
8186  From F<vendorarch.U>:
8187  
8188  This variable contains the value of the C<PERL_VENDORARCH> symbol.
8189  It may have a F<~> on the front.
8190  The standard distribution will put nothing in this directory.
8191  Vendors who distribute perl may wish to place their own
8192  architecture-dependent modules and extensions in this directory with
8193  MakeMaker F<Makefile.PL> C<INSTALLDIRS>=vendor
8194  or equivalent.  See C<INSTALL> for details.
8195  
8196  =item C<vendorarchexp>
8197  
8198  From F<vendorarch.U>:
8199  
8200  This variable is the F<~name> expanded version of vendorarch, so that you
8201  may use it directly in Makefiles or shell scripts.
8202  
8203  =item C<vendorbin>
8204  
8205  From F<vendorbin.U>:
8206  
8207  This variable contains the eventual value of the C<VENDORBIN> symbol.
8208  It may have a F<~> on the front.
8209  The standard distribution will put nothing in this directory.
8210  Vendors who distribute perl may wish to place additional
8211  binaries in this directory with
8212  MakeMaker F<Makefile.PL> C<INSTALLDIRS>=vendor
8213  or equivalent.  See C<INSTALL> for details.
8214  
8215  =item C<vendorbinexp>
8216  
8217  From F<vendorbin.U>:
8218  
8219  This variable is the F<~name> expanded version of vendorbin, so that you
8220  may use it directly in Makefiles or shell scripts.
8221  
8222  =item C<vendorhtml1dir>
8223  
8224  From F<vendorhtml1dir.U>:
8225  
8226  This variable contains the name of the directory for html
8227  pages.  It may have a F<~> on the front.
8228  The standard distribution will put nothing in this directory.
8229  Vendors who distribute perl may wish to place their own
8230  html pages in this directory with
8231  MakeMaker F<Makefile.PL> C<INSTALLDIRS>=vendor
8232  or equivalent.  See C<INSTALL> for details.
8233  
8234  =item C<vendorhtml1direxp>
8235  
8236  From F<vendorhtml1dir.U>:
8237  
8238  This variable is the F<~name> expanded version of vendorhtml1dir, so that you
8239  may use it directly in Makefiles or shell scripts.
8240  
8241  =item C<vendorhtml3dir>
8242  
8243  From F<vendorhtml3dir.U>:
8244  
8245  This variable contains the name of the directory for html
8246  library pages.  It may have a F<~> on the front.
8247  The standard distribution will put nothing in this directory.
8248  Vendors who distribute perl may wish to place their own
8249  html pages for modules and extensions in this directory with
8250  MakeMaker F<Makefile.PL> C<INSTALLDIRS>=vendor
8251  or equivalent.  See C<INSTALL> for details.
8252  
8253  =item C<vendorhtml3direxp>
8254  
8255  From F<vendorhtml3dir.U>:
8256  
8257  This variable is the F<~name> expanded version of vendorhtml3dir, so that you
8258  may use it directly in Makefiles or shell scripts.
8259  
8260  =item C<vendorlib>
8261  
8262  From F<vendorlib.U>:
8263  
8264  This variable contains the eventual value of the C<VENDORLIB> symbol,
8265  which is the name of the private library for this package.
8266  The standard distribution will put nothing in this directory.
8267  Vendors who distribute perl may wish to place their own
8268  modules in this directory with
8269  MakeMaker F<Makefile.PL> C<INSTALLDIRS>=vendor
8270  or equivalent.  See C<INSTALL> for details.
8271  
8272  =item C<vendorlib_stem>
8273  
8274  From F<vendorlib.U>:
8275  
8276  This variable is $vendorlibexp with any trailing version-specific component
8277  removed.  The elements in inc_version_list (F<inc_version_list.U>) can
8278  be tacked onto this variable to generate a list of directories to search.
8279  
8280  =item C<vendorlibexp>
8281  
8282  From F<vendorlib.U>:
8283  
8284  This variable is the F<~name> expanded version of vendorlib, so that you
8285  may use it directly in Makefiles or shell scripts.
8286  
8287  =item C<vendorman1dir>
8288  
8289  From F<vendorman1dir.U>:
8290  
8291  This variable contains the name of the directory for man1
8292  pages.  It may have a F<~> on the front.
8293  The standard distribution will put nothing in this directory.
8294  Vendors who distribute perl may wish to place their own
8295  man1 pages in this directory with
8296  MakeMaker F<Makefile.PL> C<INSTALLDIRS>=vendor
8297  or equivalent.  See C<INSTALL> for details.
8298  
8299  =item C<vendorman1direxp>
8300  
8301  From F<vendorman1dir.U>:
8302  
8303  This variable is the F<~name> expanded version of vendorman1dir, so that you
8304  may use it directly in Makefiles or shell scripts.
8305  
8306  =item C<vendorman3dir>
8307  
8308  From F<vendorman3dir.U>:
8309  
8310  This variable contains the name of the directory for man3
8311  pages.  It may have a F<~> on the front.
8312  The standard distribution will put nothing in this directory.
8313  Vendors who distribute perl may wish to place their own
8314  man3 pages in this directory with
8315  MakeMaker F<Makefile.PL> C<INSTALLDIRS>=vendor
8316  or equivalent.  See C<INSTALL> for details.
8317  
8318  =item C<vendorman3direxp>
8319  
8320  From F<vendorman3dir.U>:
8321  
8322  This variable is the F<~name> expanded version of vendorman3dir, so that you
8323  may use it directly in Makefiles or shell scripts.
8324  
8325  =item C<vendorprefix>
8326  
8327  From F<vendorprefix.U>:
8328  
8329  This variable holds the full absolute path of the directory below
8330  which the vendor will install add-on packages.
8331  See C<INSTALL> for usage and examples.
8332  
8333  =item C<vendorprefixexp>
8334  
8335  From F<vendorprefix.U>:
8336  
8337  This variable holds the full absolute path of the directory below
8338  which the vendor will install add-on packages.  Derived from vendorprefix.
8339  
8340  =item C<vendorscript>
8341  
8342  From F<vendorscript.U>:
8343  
8344  This variable contains the eventual value of the C<VENDORSCRIPT> symbol.
8345  It may have a F<~> on the front.
8346  The standard distribution will put nothing in this directory.
8347  Vendors who distribute perl may wish to place additional
8348  executable scripts in this directory with
8349  MakeMaker F<Makefile.PL> C<INSTALLDIRS>=vendor
8350  or equivalent.  See C<INSTALL> for details.
8351  
8352  =item C<vendorscriptexp>
8353  
8354  From F<vendorscript.U>:
8355  
8356  This variable is the F<~name> expanded version of vendorscript, so that you
8357  may use it directly in Makefiles or shell scripts.
8358  
8359  =item C<version>
8360  
8361  From F<patchlevel.U>:
8362  
8363  The full version number of this package, such as 5.6.1 (or 5_6_1).
8364  This combines revision, patchlevel, and subversion to get the
8365  full version number, including any possible subversions.
8366  This is suitable for use as a directory name, and hence is
8367  filesystem dependent.
8368  
8369  =item C<version_patchlevel_string>
8370  
8371  From F<patchlevel.U>:
8372  
8373  This is a string combining version, subversion and
8374  perl_patchlevel (if perl_patchlevel is non-zero).
8375  It is typically something like
8376  'version 7 subversion 1'  or
8377  'version 7 subversion 1 patchlevel 11224'
8378  It is computed here to avoid duplication of code in F<myconfig.SH>
8379  and F<lib/Config.pm>.
8380  
8381  =item C<versiononly>
8382  
8383  From F<versiononly.U>:
8384  
8385  If set, this symbol indicates that only the version-specific
8386  components of a perl installation should be installed.
8387  This may be useful for making a test installation of a new
8388  version without disturbing the existing installation.
8389  Setting versiononly is equivalent to setting installperl's -v option.
8390  In particular, the non-versioned scripts and programs such as
8391  a2p, c2ph, h2xs, pod2*, and perldoc are not installed
8392  (see C<INSTALL> for a more complete list).  Nor are the man
8393  pages installed.
8394  Usually, this is undef.
8395  
8396  =item C<vi>
8397  
8398  From F<Loc.U>:
8399  
8400  This variable is defined but not used by Configure.
8401  The value is a plain '' and is not useful.
8402  
8403  =item C<voidflags>
8404  
8405  From F<voidflags.U>:
8406  
8407  This variable contains the eventual value of the C<VOIDFLAGS> symbol,
8408  which indicates how much support of the void type is given by this
8409  compiler.  See C<VOIDFLAGS> for more info.
8410  
8411  =back
8412  
8413  =head2 x
8414  
8415  =over 4
8416  
8417  =item C<xlibpth>
8418  
8419  From F<libpth.U>:
8420  
8421  This variable holds extra path (space-separated) used to find
8422  libraries on this platform, for example C<CPU>-specific libraries
8423  (on multi-C<CPU> platforms) may be listed here.
8424  
8425  =back
8426  
8427  =head2 y
8428  
8429  =over 4
8430  
8431  =item C<yacc>
8432  
8433  From F<yacc.U>:
8434  
8435  This variable holds the name of the compiler compiler we
8436  want to use in the Makefile. It can be yacc, byacc, or bison -y.
8437  
8438  =item C<yaccflags>
8439  
8440  From F<yacc.U>:
8441  
8442  This variable contains any additional yacc flags desired by the
8443  user.  It is up to the Makefile to use this.
8444  
8445  =back
8446  
8447  =head2 z
8448  
8449  =over 4
8450  
8451  =item C<zcat>
8452  
8453  From F<Loc.U>:
8454  
8455  This variable is defined but not used by Configure.
8456  The value is a plain '' and is not useful.
8457  
8458  =item C<zip>
8459  
8460  From F<Loc.U>:
8461  
8462  This variable is used internally by Configure to determine the
8463  full pathname (if any) of the zip program.  After Configure runs,
8464  the value is reset to a plain C<zip> and is not useful.
8465  
8466  
8467  =back
8468  
8469  =head1 NOTE
8470  
8471  This module contains a good example of how to use tie to implement a
8472  cache and an example of how to make a tied variable readonly to those
8473  outside of it.
8474  
8475  =cut
8476