Allow testing of DBM_Filter with any *DBM_File

[p5sagit/p5-mst-13.2.git] / configpm

#!./miniperl -w
#
# configpm
#
# Copyright (C) 1994, 1995, 1996 1997, 1998, 1999, 2000, 2001,
# 2002, 2003, 2004, 2005, 2006 Larry Wall and others.
#
#
# Regenerate the files
#
#    lib/Config.pm
#    lib/Config_heavy.pl
#    lib/Config.pod
#    lib/Cross.pm (optionally)
#
# from the contents of the static files
#
#    Porting/Glossary
#    myconfig.SH
#
# and from the contents of the Configure-generated file
#
#    config.sh
#
# It will only update Config.pm and Config_heavy.pl if the contents of
# either file would be different. Note that *both* files are updated in
# this case, since for example an extension makefile that has a dependency
# on Config.pm should trigger even if only Config_heavy.pl has changed.

sub usage { die <<EOF }
usage: $0  [ options ] [ Config_file ] [ Glossary_file ]
    --cross=PLATFORM    cross-compile for a different platform
    --no-glossary       don't include Porting/Glossary in lib/Config.pod
    --heavy=FILE        alternative name for lib/Config_heavy.pl
    Config_file         alternative name for lib/Config.pm
    Glossary_file       alternative name for Porting/Glossary
EOF

use strict;
use vars qw(%Config $Config_SH_expanded);

my $how_many_common = 22;

# commonly used names to precache (and hence lookup fastest)
my %Common;

while ($how_many_common--) {
    $_ = <DATA>;
    chomp;
    /^(\S+):\s*(\d+)$/ or die "Malformed line '$_'";
    $Common{$1} = $1;
}

# names of things which may need to have slashes changed to double-colons
my %Extensions = map {($_,$_)}
                 qw(dynamic_ext static_ext extensions known_extensions);

# allowed opts as well as specifies default and initial values
my %Allowed_Opts = (
    'cross'    => '', # --cross=PLATFORM - crosscompiling for PLATFORM
    'glossary' => 1,  # --no-glossary  - no glossary file inclusion,
                      #                  for compactness
    'heavy' => '',   # pathname of the Config_heavy.pl file
);

sub opts {
    # user specified options
    my %given_opts = (
        # --opt=smth
        (map {/^--([\-_\w]+)=(.*)$/} @ARGV),
        # --opt --no-opt --noopt
        (map {/^no-?(.*)$/i?($1=>0):($_=>1)} map {/^--([\-_\w]+)$/} @ARGV),
    );

    my %opts = (%Allowed_Opts, %given_opts);

    for my $opt (grep {!exists $Allowed_Opts{$_}} keys %given_opts) {
        warn "option '$opt' is not recognized";
	usage;
    }
    @ARGV = grep {!/^--/} @ARGV;

    return %opts;
}


my %Opts = opts();

my ($Config_PM, $Config_heavy);
my $Glossary = $ARGV[1] || 'Porting/Glossary';

if ($Opts{cross}) {
  # creating cross-platform config file
  mkdir "xlib";
  mkdir "xlib/$Opts{cross}";
  $Config_PM = $ARGV[0] || "xlib/$Opts{cross}/Config.pm";
}
else {
  $Config_PM = $ARGV[0] || 'lib/Config.pm';
}
if ($Opts{heavy}) {
  $Config_heavy = $Opts{heavy};
}
else {
  ($Config_heavy = $Config_PM) =~ s!\.pm$!_heavy.pl!;
  die "Can't automatically determine name for Config_heavy.pl from '$Config_PM'"
    if $Config_heavy eq $Config_PM;
}

my $config_txt;
my $heavy_txt;

$heavy_txt .= <<'ENDOFBEG';
# This file was created by configpm when Perl was built. Any changes
# made to this file will be lost the next time perl is built.

package Config;
use strict;
# use warnings; Pulls in Carp
# use vars pulls in Carp
ENDOFBEG

my $myver = sprintf "%vd", $^V;

$config_txt .= sprintf <<'ENDOFBEG', ($myver) x 3;
# This file was created by configpm when Perl was built. Any changes
# made to this file will be lost the next time perl is built.

package Config;
use strict;
# use warnings; Pulls in Carp
# use vars pulls in Carp
@Config::EXPORT = qw(%%Config);
@Config::EXPORT_OK = qw(myconfig config_sh config_vars config_re);

# Need to stub all the functions to make code such as print Config::config_sh
# keep working

sub myconfig;
sub config_sh;
sub config_vars;
sub config_re;

my %%Export_Cache = map {($_ => 1)} (@Config::EXPORT, @Config::EXPORT_OK);

our %%Config;

# Define our own import method to avoid pulling in the full Exporter:
sub import {
    my $pkg = shift;
    @_ = @Config::EXPORT unless @_;

    my @funcs = grep $_ ne '%%Config', @_;
    my $export_Config = @funcs < @_ ? 1 : 0;

    no strict 'refs';
    my $callpkg = caller(0);
    foreach my $func (@funcs) {
	die sprintf qq{"%%s" is not exported by the %%s module\n},
	    $func, __PACKAGE__ unless $Export_Cache{$func};
	*{$callpkg.'::'.$func} = \&{$func};
    }

    *{"$callpkg\::Config"} = \%%Config if $export_Config;
    return;
}

die "Perl lib version (%s) doesn't match executable version ($])"
    unless $^V;

$^V eq %s
    or die "Perl lib version (%s) doesn't match executable version (" .
	sprintf("v%%vd",$^V) . ")";

ENDOFBEG


my @non_v    = ();
my @v_others = ();
my $in_v     = 0;
my %Data     = ();


my %seen_quotes;
{
  my ($name, $val);
  open(CONFIG_SH, 'config.sh') || die "Can't open config.sh: $!";
  while (<CONFIG_SH>) {
    next if m:^#!/bin/sh:;

    # Catch PERL_CONFIG_SH=true and PERL_VERSION=n line from Configure.
    s/^(\w+)=(true|\d+)\s*$/$1='$2'\n/ or m/^(\w+)='(.*)'$/;
    my($k, $v) = ($1, $2);

    # grandfather PATCHLEVEL and SUBVERSION and CONFIG
    if ($k) {
	if ($k eq 'PERL_VERSION') {
	    push @v_others, "PATCHLEVEL='$v'\n";
	}
	elsif ($k eq 'PERL_SUBVERSION') {
	    push @v_others, "SUBVERSION='$v'\n";
	}
	elsif ($k eq 'PERL_CONFIG_SH') {
	    push @v_others, "CONFIG='$v'\n";
	}
    }

    # We can delimit things in config.sh with either ' or ". 
    unless ($in_v or m/^(\w+)=(['"])(.*\n)/){
	push(@non_v, "#$_"); # not a name='value' line
	next;
    }
    my $quote = $2;
    if ($in_v) { 
        $val .= $_;
    }
    else { 
        ($name,$val) = ($1,$3); 
    }
    $in_v = $val !~ /$quote\n/;
    next if $in_v;

    s,/,::,g if $Extensions{$name};

    $val =~ s/$quote\n?\z//;

    my $line = "$name=$quote$val$quote\n";
    push(@v_others, $line);
    $seen_quotes{$quote}++;
  }
  close CONFIG_SH;
}

# This is somewhat grim, but I want the code for parsing config.sh here and
# now so that I can expand $Config{ivsize} and $Config{ivtype}

my $fetch_string = <<'EOT';

# Search for it in the big string
sub fetch_string {
    my($self, $key) = @_;

EOT

if ($seen_quotes{'"'}) {
    # We need the full ' and " code
    $fetch_string .= <<'EOT';
    my $quote_type = "'";
    my $marker = "$key=";

    # Check for the common case, ' delimited
    my $start = index($Config_SH_expanded, "\n$marker$quote_type");
    # If that failed, check for " delimited
    if ($start == -1) {
        $quote_type = '"';
        $start = index($Config_SH_expanded, "\n$marker$quote_type");
    }
EOT
} else {
    $fetch_string .= <<'EOT';
    # We only have ' delimted.
    my $start = index($Config_SH_expanded, "\n$key=\'");
EOT
}
$fetch_string .= <<'EOT';
    # Start can never be -1 now, as we've rigged the long string we're
    # searching with an initial dummy newline.
    return undef if $start == -1;

    $start += length($key) + 3;

EOT
if (!$seen_quotes{'"'}) {
    # Don't need the full ' and " code, or the eval expansion.
    $fetch_string .= <<'EOT';
    my $value = substr($Config_SH_expanded, $start,
                       index($Config_SH_expanded, "'\n", $start)
		       - $start);
EOT
} else {
    $fetch_string .= <<'EOT';
    my $value = substr($Config_SH_expanded, $start,
                       index($Config_SH_expanded, "$quote_type\n", $start)
		       - $start);

    # If we had a double-quote, we'd better eval it so escape
    # sequences and such can be interpolated. Since the incoming
    # value is supposed to follow shell rules and not perl rules,
    # we escape any perl variable markers
    if ($quote_type eq '"') {
	$value =~ s/\$/\\\$/g;
	$value =~ s/\@/\\\@/g;
	eval "\$value = \"$value\"";
    }
EOT
}
$fetch_string .= <<'EOT';
    # So we can say "if $Config{'foo'}".
    $value = undef if $value eq 'undef';
    $self->{$key} = $value; # cache it
}
EOT

eval $fetch_string;
die if $@;

# Calculation for the keys for byteorder
# This is somewhat grim, but I need to run fetch_string here.
our $Config_SH_expanded = join "\n", '', @v_others;

my $t = fetch_string ({}, 'ivtype');
my $s = fetch_string ({}, 'ivsize');

# byteorder does exist on its own but we overlay a virtual
# dynamically recomputed value.

# However, ivtype and ivsize will not vary for sane fat binaries

my $f = $t eq 'long' ? 'L!' : $s == 8 ? 'Q': 'I';

my $byteorder_code;
if ($s == 4 || $s == 8) {
    my $list = join ',', reverse(2..$s);
    my $format = 'a'x$s;
    $byteorder_code = <<"EOT";

my \$i = 0;
foreach my \$c ($list) { \$i |= ord(\$c); \$i <<= 8 }
\$i |= ord(1);
our \$byteorder = join('', unpack('$format', pack('$f', \$i)));
EOT
} else {
    $byteorder_code = "our \$byteorder = '?'x$s;\n";
}

my @need_relocation;

if (fetch_string({},'userelocatableinc')) {
    foreach my $what (qw(prefixexp

			 archlibexp
			 html1direxp
			 html3direxp
			 man1direxp
			 man3direxp
			 privlibexp
			 scriptdirexp
			 sitearchexp
			 sitebinexp
			 sitehtml1direxp
			 sitehtml3direxp
			 sitelibexp
			 siteman1direxp
			 siteman3direxp
			 sitescriptexp
			 vendorarchexp
			 vendorbinexp
			 vendorhtml1direxp
			 vendorhtml3direxp
			 vendorlibexp
			 vendorman1direxp
			 vendorman3direxp
			 vendorscriptexp

			 siteprefixexp
			 sitelib_stem
			 vendorlib_stem

			 installarchlib
			 installhtml1dir
			 installhtml3dir
			 installman1dir
			 installman3dir
			 installprefix
			 installprefixexp
			 installprivlib
			 installscript
			 installsitearch
			 installsitebin
			 installsitehtml1dir
			 installsitehtml3dir
			 installsitelib
			 installsiteman1dir
			 installsiteman3dir
			 installsitescript
			 installvendorarch
			 installvendorbin
			 installvendorhtml1dir
			 installvendorhtml3dir
			 installvendorlib
			 installvendorman1dir
			 installvendorman3dir
			 installvendorscript
			 )) {
	push @need_relocation, $what if fetch_string({}, $what) =~ m!^\.\.\./!;
    }
}

my %need_relocation;
@need_relocation{@need_relocation} = @need_relocation;

# This can have .../ anywhere:
if (fetch_string({}, 'otherlibdirs') =~ m!\.\.\./!) {
    $need_relocation{otherlibdirs} = 'otherlibdirs';
}

my $relocation_code = <<'EOT';

sub relocate_inc {
  my $libdir = shift;
  return $libdir unless $libdir =~ s!^\.\.\./!!;
  my $prefix = $^X;
  if ($prefix =~ s!/[^/]*$!!) {
    while ($libdir =~ m!^\.\./!) {
      # Loop while $libdir starts "../" and $prefix still has a trailing
      # directory
      last unless $prefix =~ s!/([^/]+)$!!;
      # but bail out if the directory we picked off the end of $prefix is .
      # or ..
      if ($1 eq '.' or $1 eq '..') {
	# Undo! This should be rare, hence code it this way rather than a
	# check each time before the s!!! above.
	$prefix = "$prefix/$1";
	last;
      }
      # Remove that leading ../ and loop again
      substr ($libdir, 0, 3, '');
    }
    $libdir = "$prefix/$libdir";
  }
  $libdir;
}
EOT

if (%need_relocation) {
  my $relocations_in_common;
  # otherlibdirs only features in the hash
  foreach (keys %need_relocation) {
    $relocations_in_common++ if $Common{$_};
  }
  if ($relocations_in_common) {
    $config_txt .= $relocation_code;
  } else {
    $heavy_txt .= $relocation_code;
  }
}

$heavy_txt .= join('', @non_v) . "\n";

# copy config summary format from the myconfig.SH script
$heavy_txt .= "our \$summary = <<'!END!';\n";
open(MYCONFIG,"<myconfig.SH") || die "open myconfig.SH failed: $!";
1 while defined($_ = <MYCONFIG>) && !/^Summary of/;
do { $heavy_txt .= $_ } until !defined($_ = <MYCONFIG>) || /^\s*$/;
close(MYCONFIG);

$heavy_txt .= "\n!END!\n" . <<'EOT';
my $summary_expanded;

sub myconfig {
    return $summary_expanded if $summary_expanded;
    ($summary_expanded = $summary) =~ s{\$(\w+)}
		 { my $c = $Config::Config{$1}; defined($c) ? $c : 'undef' }ge;
    $summary_expanded;
}

local *_ = \my $a;
$_ = <<'!END!';
EOT

$heavy_txt .= join('', sort @v_others) . "!END!\n";

# Only need the dynamic byteorder code in Config.pm if 'byteorder' is one of
# the precached keys
if ($Common{byteorder}) {
    $config_txt .= $byteorder_code;
} else {
    $heavy_txt .= $byteorder_code;
}

if (@need_relocation) {
$heavy_txt .= 'foreach my $what (qw(' . join (' ', @need_relocation) .
      ")) {\n" . <<'EOT';
    s/^($what=)(['"])(.*?)\2/$1 . $2 . relocate_inc($3) . $2/me;
}
EOT
# Currently it only makes sense to do the ... relocation on Unix, so there's
# no need to emulate the "which separator for this platform" logic in perl.c -
# ':' will always be applicable
if ($need_relocation{otherlibdirs}) {
$heavy_txt .= << 'EOT';
s{^(otherlibdirs=)(['"])(.*?)\2}
 {$1 . $2 . join ':', map {relocate_inc($_)} split ':', $3 . $2}me;
EOT
}
}

$heavy_txt .= <<'EOT';
s/(byteorder=)(['"]).*?\2/$1$2$Config::byteorder$2/m;

my $config_sh_len = length $_;

our $Config_SH_expanded = "\n$_" . << 'EOVIRTUAL';
EOT

foreach my $prefix (qw(ccflags ldflags)) {
    my $value = fetch_string ({}, $prefix);
    my $withlargefiles = fetch_string ({}, $prefix . "_uselargefiles");
    if (defined $withlargefiles) {
        $value =~ s/\Q$withlargefiles\E\b//;
        $heavy_txt .= "${prefix}_nolargefiles='$value'\n";
    }
}

foreach my $prefix (qw(libs libswanted)) {
    my $value = fetch_string ({}, $prefix);
    my $withlf = fetch_string ({}, 'libswanted_uselargefiles');
    next unless defined $withlf;
    my @lflibswanted
       = split(' ', fetch_string ({}, 'libswanted_uselargefiles'));
    if (@lflibswanted) {
	my %lflibswanted;
	@lflibswanted{@lflibswanted} = ();
	if ($prefix eq 'libs') {
	    my @libs = grep { /^-l(.+)/ &&
                            not exists $lflibswanted{$1} }
		                    split(' ', fetch_string ({}, 'libs'));
	    $value = join(' ', @libs);
	} else {
	    my @libswanted = grep { not exists $lflibswanted{$_} }
	                          split(' ', fetch_string ({}, 'libswanted'));
	    $value = join(' ', @libswanted);
	}
    }
    $heavy_txt .= "${prefix}_nolargefiles='$value'\n";
}

$heavy_txt .= "EOVIRTUAL\n";

$heavy_txt .= $fetch_string;

$config_txt .= <<'ENDOFEND';

sub FETCH {
    my($self, $key) = @_;

    # check for cached value (which may be undef so we use exists not defined)
    return $self->{$key} if exists $self->{$key};

    return $self->fetch_string($key);
}
ENDOFEND

$heavy_txt .= <<'ENDOFEND';

my $prevpos = 0;

sub FIRSTKEY {
    $prevpos = 0;
    substr($Config_SH_expanded, 1, index($Config_SH_expanded, '=') - 1 );
}

sub NEXTKEY {
ENDOFEND
if ($seen_quotes{'"'}) {
$heavy_txt .= <<'ENDOFEND';
    # Find out how the current key's quoted so we can skip to its end.
    my $quote = substr($Config_SH_expanded,
		       index($Config_SH_expanded, "=", $prevpos)+1, 1);
    my $pos = index($Config_SH_expanded, qq($quote\n), $prevpos) + 2;
ENDOFEND
} else {
    # Just ' quotes, so it's much easier.
$heavy_txt .= <<'ENDOFEND';
    my $pos = index($Config_SH_expanded, qq('\n), $prevpos) + 2;
ENDOFEND
}
$heavy_txt .= <<'ENDOFEND';
    my $len = index($Config_SH_expanded, "=", $pos) - $pos;
    $prevpos = $pos;
    $len > 0 ? substr($Config_SH_expanded, $pos, $len) : undef;
}

sub EXISTS {
    return 1 if exists($_[0]->{$_[1]});

    return(index($Config_SH_expanded, "\n$_[1]='") != -1
ENDOFEND
if ($seen_quotes{'"'}) {
$heavy_txt .= <<'ENDOFEND';
           or index($Config_SH_expanded, "\n$_[1]=\"") != -1
ENDOFEND
}
$heavy_txt .= <<'ENDOFEND';
          );
}

sub STORE  { die "\%Config::Config is read-only\n" }
*DELETE = \&STORE;
*CLEAR  = \&STORE;


sub config_sh {
    substr $Config_SH_expanded, 1, $config_sh_len;
}

sub config_re {
    my $re = shift;
    return map { chomp; $_ } grep eval{ /^(?:$re)=/ }, split /^/,
    $Config_SH_expanded;
}

sub config_vars {
    # implements -V:cfgvar option (see perlrun -V:)
    foreach (@_) {
	# find optional leading, trailing colons; and query-spec
	my ($notag,$qry,$lncont) = m/^(:)?(.*?)(:)?$/;	# flags fore and aft, 
	# map colon-flags to print decorations
	my $prfx = $notag ? '': "$qry=";		# tag-prefix for print
	my $lnend = $lncont ? ' ' : ";\n";		# line ending for print

	# all config-vars are by definition \w only, any \W means regex
	if ($qry =~ /\W/) {
	    my @matches = config_re($qry);
	    print map "$_$lnend", @matches ? @matches : "$qry: not found"		if !$notag;
	    print map { s/\w+=//; "$_$lnend" } @matches ? @matches : "$qry: not found"	if  $notag;
	} else {
	    my $v = (exists $Config::Config{$qry}) ? $Config::Config{$qry}
						   : 'UNKNOWN';
	    $v = 'undef' unless defined $v;
	    print "${prfx}'${v}'$lnend";
	}
    }
}

# Called by the real AUTOLOAD
sub launcher {
    undef &AUTOLOAD;
    goto \&$Config::AUTOLOAD;
}

1;
ENDOFEND

if ($^O eq 'os2') {
    $config_txt .= <<'ENDOFSET';
my %preconfig;
if ($OS2::is_aout) {
    my ($value, $v) = $Config_SH_expanded =~ m/^used_aout='(.*)'\s*$/m;
    for (split ' ', $value) {
        ($v) = $Config_SH_expanded =~ m/^aout_$_='(.*)'\s*$/m;
        $preconfig{$_} = $v eq 'undef' ? undef : $v;
    }
}
$preconfig{d_fork} = undef unless $OS2::can_fork; # Some funny cases can't
sub TIEHASH { bless {%preconfig} }
ENDOFSET
    # Extract the name of the DLL from the makefile to avoid duplication
    my ($f) = grep -r, qw(GNUMakefile Makefile);
    my $dll;
    if (open my $fh, '<', $f) {
	while (<$fh>) {
	    $dll = $1, last if /^PERL_DLL_BASE\s*=\s*(\S*)\s*$/;
	}
    }
    $config_txt .= <<ENDOFSET if $dll;
\$preconfig{dll_name} = '$dll';
ENDOFSET
} else {
    $config_txt .= <<'ENDOFSET';
sub TIEHASH {
    bless $_[1], $_[0];
}
ENDOFSET
}

foreach my $key (keys %Common) {
    my $value = fetch_string ({}, $key);
    # Is it safe on the LHS of => ?
    my $qkey = $key =~ /^[A-Za-z_][A-Za-z0-9_]*$/ ? $key : "'$key'";
    if (defined $value) {
	# Quote things for a '' string
	$value =~ s!\\!\\\\!g;
	$value =~ s!'!\\'!g;
	$value = "'$value'";
	if ($key eq 'otherlibdirs') {
	    $value = "join (':', map {relocate_inc(\$_)} split (':', $value))";
	} elsif ($need_relocation{$key}) {
	    $value = "relocate_inc($value)";
	}
    } else {
	$value = "undef";
    }
    $Common{$key} = "$qkey => $value";
}

if ($Common{byteorder}) {
    $Common{byteorder} = 'byteorder => $byteorder';
}
my $fast_config = join '', map { "    $_,\n" } sort values %Common;

# Sanity check needed to stop an infite loop if Config_heavy.pl fails to define
# &launcher for some reason (eg it got truncated)
$config_txt .= sprintf <<'ENDOFTIE', $fast_config;

sub DESTROY { }

sub AUTOLOAD {
    require 'Config_heavy.pl';
    goto \&launcher unless $Config::AUTOLOAD =~ /launcher$/;
    die "&Config::AUTOLOAD failed on $Config::AUTOLOAD";
}

# tie returns the object, so the value returned to require will be true.
tie %%Config, 'Config', {
%s};
ENDOFTIE


open(CONFIG_POD, ">lib/Config.pod") or die "Can't open lib/Config.pod: $!";
print CONFIG_POD <<'ENDOFTAIL';
=head1 NAME

Config - access Perl configuration information

=head1 SYNOPSIS

    use Config;
    if ($Config{usethreads}) {
	print "has thread support\n"
    } 

    use Config qw(myconfig config_sh config_vars config_re);

    print myconfig();

    print config_sh();

    print config_re();

    config_vars(qw(osname archname));


=head1 DESCRIPTION

The Config module contains all the information that was available to
the C<Configure> program at Perl build time (over 900 values).

Shell variables from the F<config.sh> file (written by Configure) are
stored in the readonly-variable C<%Config>, indexed by their names.

Values stored in config.sh as 'undef' are returned as undefined
values.  The perl C<exists> function can be used to check if a
named variable exists.

=over 4

=item myconfig()

Returns a textual summary of the major perl configuration values.
See also C<-V> in L<perlrun/Switches>.

=item config_sh()

Returns the entire perl configuration information in the form of the
original config.sh shell variable assignment script.

=item config_re($regex)

Like config_sh() but returns, as a list, only the config entries who's
names match the $regex.

=item config_vars(@names)

Prints to STDOUT the values of the named configuration variable. Each is
printed on a separate line in the form:

  name='value';

Names which are unknown are output as C<name='UNKNOWN';>.
See also C<-V:name> in L<perlrun/Switches>.

=back

=head1 EXAMPLE

Here's a more sophisticated example of using %Config:

    use Config;
    use strict;

    my %sig_num;
    my @sig_name;
    unless($Config{sig_name} && $Config{sig_num}) {
	die "No sigs?";
    } else {
	my @names = split ' ', $Config{sig_name};
	@sig_num{@names} = split ' ', $Config{sig_num};
	foreach (@names) {
	    $sig_name[$sig_num{$_}] ||= $_;
	}   
    }

    print "signal #17 = $sig_name[17]\n";
    if ($sig_num{ALRM}) { 
	print "SIGALRM is $sig_num{ALRM}\n";
    }   

=head1 WARNING

Because this information is not stored within the perl executable
itself it is possible (but unlikely) that the information does not
relate to the actual perl binary which is being used to access it.

The Config module is installed into the architecture and version
specific library directory ($Config{installarchlib}) and it checks the
perl version number when loaded.

The values stored in config.sh may be either single-quoted or
double-quoted. Double-quoted strings are handy for those cases where you
need to include escape sequences in the strings. To avoid runtime variable
interpolation, any C<$> and C<@> characters are replaced by C<\$> and
C<\@>, respectively. This isn't foolproof, of course, so don't embed C<\$>
or C<\@> in double-quoted strings unless you're willing to deal with the
consequences. (The slashes will end up escaped and the C<$> or C<@> will
trigger variable interpolation)

=head1 GLOSSARY

Most C<Config> variables are determined by the C<Configure> script
on platforms supported by it (which is most UNIX platforms).  Some
platforms have custom-made C<Config> variables, and may thus not have
some of the variables described below, or may have extraneous variables
specific to that particular port.  See the port specific documentation
in such cases.

ENDOFTAIL

if ($Opts{glossary}) {
  open(GLOS, "<$Glossary") or die "Can't open $Glossary: $!";
}
my %seen = ();
my $text = 0;
$/ = '';

sub process {
  if (s/\A(\w*)\s+\(([\w.]+)\):\s*\n(\t?)/=item C<$1>\n\nFrom F<$2>:\n\n/m) {
    my $c = substr $1, 0, 1;
    unless ($seen{$c}++) {
      print CONFIG_POD <<EOF if $text;
=back

EOF
      print CONFIG_POD <<EOF;
=head2 $c

=over 4

EOF
     $text = 1;
    }
  }
  elsif (!$text || !/\A\t/) {
    warn "Expected a Configure variable header",
      ($text ? " or another paragraph of description" : () );
  }
  s/n't/n\00t/g;		# leave can't, won't etc untouched
  s/^\t\s+(.*)/\n$1/gm;		# Indented lines ===> new paragraph
  s/^(?<!\n\n)\t(.*)/$1/gm;	# Not indented lines ===> text
  s{([\'\"])(?=[^\'\"\s]*[./][^\'\"\s]*\1)([^\'\"\s]+)\1}(F<$2>)g; # '.o'
  s{([\'\"])([^\'\"\s]+)\1}(C<$2>)g; # "date" command
  s{\'([A-Za-z_\- *=/]+)\'}(C<$1>)g; # 'ln -s'
  s{
     (?<! [\w./<\'\"] )		# Only standalone file names
     (?! e \. g \. )		# Not e.g.
     (?! \. \. \. )		# Not ...
     (?! \d )			# Not 5.004
     (?! read/ )		# Not read/write
     (?! etc\. )		# Not etc.
     (?! I/O )			# Not I/O
     (
	\$ ?			# Allow leading $
	[\w./]* [./] [\w./]*	# Require . or / inside
     )
     (?<! \. (?= [\s)] ) )	# Do not include trailing dot
     (?! [\w/] )		# Include all of it
   }
   (F<$1>)xg;			# /usr/local
  s/((?<=\s)~\w*)/F<$1>/g;	# ~name
  s/(?<![.<\'\"])\b([A-Z_]{2,})\b(?![\'\"])/C<$1>/g;	# UNISTD
  s/(?<![.<\'\"])\b(?!the\b)(\w+)\s+macro\b/C<$1> macro/g; # FILE_cnt macro
  s/n[\0]t/n't/g;		# undo can't, won't damage
}

if ($Opts{glossary}) {
    <GLOS>;				# Skip the "DO NOT EDIT"
    <GLOS>;				# Skip the preamble
  while (<GLOS>) {
    process;
    print CONFIG_POD;
  }
}

print CONFIG_POD <<'ENDOFTAIL';

=back

=head1 NOTE

This module contains a good example of how to use tie to implement a
cache and an example of how to make a tied variable readonly to those
outside of it.

=cut

ENDOFTAIL

close(GLOS) if $Opts{glossary};
close(CONFIG_POD);
print "written lib/Config.pod\n";

my $orig_config_txt = "";
my $orig_heavy_txt = "";
{
    local $/;
    my $fh;
    $orig_config_txt = <$fh> if open $fh, "<", $Config_PM;
    $orig_heavy_txt  = <$fh> if open $fh, "<", $Config_heavy;
}

if ($orig_config_txt ne $config_txt or $orig_heavy_txt ne $heavy_txt) {
    open CONFIG, ">", $Config_PM or die "Can't open $Config_PM: $!\n";
    open CONFIG_HEAVY, ">", $Config_heavy or die "Can't open $Config_heavy: $!\n";
    print CONFIG $config_txt;
    print CONFIG_HEAVY $heavy_txt;
    close(CONFIG_HEAVY);
    close(CONFIG);
    print "updated $Config_PM\n";
    print "updated $Config_heavy\n";
}


# Now create Cross.pm if needed
if ($Opts{cross}) {
  open CROSS, ">lib/Cross.pm" or die "Can not open >lib/Cross.pm: $!";
  my $cross = <<'EOS';
# typical invocation:
#   perl -MCross Makefile.PL
#   perl -MCross=wince -V:cc
package Cross;

sub import {
  my ($package,$platform) = @_;
  unless (defined $platform) {
    # if $platform is not specified, then use last one when
    # 'configpm; was invoked with --cross option
    $platform = '***replace-marker***';
  }
  @INC = map {/\blib\b/?(do{local $_=$_;s/\blib\b/xlib\/$platform/;$_},$_):($_)} @INC;
  $::Cross::platform = $platform;
}

1;
EOS
  $cross =~ s/\*\*\*replace-marker\*\*\*/$Opts{cross}/g;
  print CROSS $cross;
  close CROSS;
  print "written lib/Cross.pm\n";
  unshift(@INC,"xlib/$Opts{cross}");
}

# Now do some simple tests on the Config.pm file we have created
unshift(@INC,'lib');
unshift(@INC,'xlib/symbian') if $Opts{cross};
require $Config_PM;
require $Config_heavy;
import Config;

die "$0: $Config_PM not valid"
	unless $Config{'PERL_CONFIG_SH'} eq 'true';

die "$0: error processing $Config_PM"
	if defined($Config{'an impossible name'})
	or $Config{'PERL_CONFIG_SH'} ne 'true' # test cache
	;

die "$0: error processing $Config_PM"
	if eval '$Config{"cc"} = 1'
	or eval 'delete $Config{"cc"}'
	;


exit 0;
# Popularity of various entries in %Config, based on a large build and test
# run of code in the Fotango build system:
__DATA__
path_sep:	8490
d_readlink:	7101
d_symlink:	7101
archlibexp:	4318
sitearchexp:	4305
sitelibexp:	4305
privlibexp:	4163
ldlibpthname:	4041
libpth:	2134
archname:	1591
exe_ext:	1256
scriptdir:	1155
version:	1116
useithreads:	1002
osvers:	982
osname:	851
inc_version_list:	783
dont_use_nlink:	779
intsize:	759
usevendorprefix:	642
dlsrc:	624
cc:	541
lib_ext:	520
so:	512
ld:	501
ccdlflags:	500
ldflags:	495
obj_ext:	495
cccdlflags:	493
lddlflags:	493
ar:	492
dlext:	492
libc:	492
ranlib:	492
full_ar:	491
vendorarchexp:	491
vendorlibexp:	491
installman1dir:	489
installman3dir:	489
installsitebin:	489
installsiteman1dir:	489
installsiteman3dir:	489
installvendorman1dir:	489
installvendorman3dir:	489
d_flexfnam:	474
eunicefix:	360
d_link:	347
installsitearch:	344
installscript:	341
installprivlib:	337
binexp:	336
installarchlib:	336
installprefixexp:	336
installsitelib:	336
installstyle:	336
installvendorarch:	336
installvendorbin:	336
installvendorlib:	336
man1ext:	336
man3ext:	336
sh:	336
siteprefixexp:	336
installbin:	335
usedl:	332
ccflags:	285
startperl:	232
optimize:	231
usemymalloc:	229
cpprun:	228
sharpbang:	228
perllibs:	225
usesfio:	224
usethreads:	220
perlpath:	218
extensions:	217
usesocks:	208
shellflags:	198
make:	191
d_pwage:	189
d_pwchange:	189
d_pwclass:	189
d_pwcomment:	189
d_pwexpire:	189
d_pwgecos:	189
d_pwpasswd:	189
d_pwquota:	189
gccversion:	189
libs:	186
useshrplib:	186
cppflags:	185
ptrsize:	185
shrpenv:	185
static_ext:	185
use5005threads:	185
uselargefiles:	185
alignbytes:	184
byteorder:	184
ccversion:	184
config_args:	184
cppminus:	184