#!/home/ben/software/install/bin/perl
use warnings;
use strict;
my $include = 'limits.h';

my %defines;
get_defines ($include, \%defines);
print_defines (\%defines);

exit;

sub get_defines
{
    my ($include, $defines) = @_;
    my $file = "/usr/include/$include";
    open my $in, "<", $file or die $!;
    while (<$in>) {
        if (/^#\s*include\s*<(.*)>/) {
            my $subinclude = $1;
            get_defines ($subinclude, $defines);
            next;
        }
        if (/^#\s*define\s+(\w*)\s+(.*)/) {
            my $macro = $1;
            my $value = $2;
            $value =~ s!\s+|/\*.*?\*/|\(|\)!!g;
            while ($defines->{$value}) {
                $value = $defines->{$value};
            }
            $defines->{$macro} = $value;
            next;
        }
    }
    close $in or die $!;
}

sub print_defines
{
    my ($defines) = @_;
    for my $k (sort keys %$defines) {
        if ($k !~ /^_/ && $k !~ /^[a-z]+$/) {
            print "$k = $defines->{$k}\n";
        }
    }
}