source: vendor/perl/5.8.8/Porting/checkcfgvar.pl

#!/usr/bin/perl -w

#
# Check that the various config.sh-clones have (at least) all the
# same symbols as the top-level config_h.SH so that the (potentially)
# needed symbols are not lagging after how Configure thinks the world
# is laid out.
#
# VMS is not handled here, due to their own rather elaborate DCL scripting.
#

use strict;

my $MASTER_CFG = "config_h.SH";
my %MASTER_CFG;

my @CFG = (
           # This list contains both 5.8.x and 5.9.x files,
           # we check from MANIFEST whether they are expected to be present.
           "Cross/config.sh-arm-linux",
           "epoc/config.sh",
           "NetWare/config.wc",
           "symbian/config.sh",
           "uconfig.sh",
           "plan9/config_sh.sample",
           "vos/config.alpha.def",
           "vos/config.ga.def",
           "win32/config.bc",
           "win32/config.gc",
           "win32/config.vc",
           "win32/config.vc64",
           "wince/config.ce",
          );

sub read_file {
    my ($fn, $sub) = @_;
    if (open(my $fh, $fn)) {
        local $_;
        while (<$fh>) {
            &$sub;
        }
    } else {
        die "$0: Failed to open '$fn' for reading: $!\n";
    }
}

sub config_h_SH_reader {
    my $cfg = shift;
    return sub {
        return if 1../^echo \"Extracting \$CONFIG_H/;
        while (/[^\\]\$(\w+)/g) {
            my $v = $1;
            next if $v =~ /^(CONFIG_H|CONFIG_SH)$/;
            $cfg->{$v}++;
        }
    }
}

read_file($MASTER_CFG,
          config_h_SH_reader(\%MASTER_CFG));

my %MANIFEST;

read_file("MANIFEST",
          sub {
              $MANIFEST{$1}++ if /^(.+?)\t/;
          });

my @MASTER_CFG = sort keys %MASTER_CFG;

sub check_cfg {
    my ($fn, $cfg) = @_;
    for my $v (@MASTER_CFG) {
        print "$fn: missing '$v'\n" unless exists $cfg->{$v};
    }
}

for my $cfg (@CFG) {
    unless (exists $MANIFEST{$cfg}) {
        print "[skipping not-expected '$cfg']\n";
        next;
    }
    my %cfg;
    read_file($cfg,
              sub {
                  return if /^\#/ || /^\s*$/;
                  # foo='bar'
                  # foo=bar
                  # $foo='bar' # VOS 5.8.x specialty
                  # $foo=bar   # VOS 5.8.x specialty
                  if (/^\$?(\w+)='(.*)'$/) {
                      $cfg{$1}++;
                  }
                  elsif (/^\$?(\w+)=(.*)$/) {
                      $cfg{$1}++;
                  } else {
                      warn "$cfg:$.:$_";
                  }
              });
    check_cfg($cfg, \%cfg);
}