Add script to generate list of errno value macros

Author: hoelzro

tools/build/generate-constants.pl

@@ -0,0 +1,43 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+
+use POSIX;
+
+print <<"END_HEADER";
+# DO NOT EDIT THIS FILE.
+#
+# This file is generated automatically from
+# $0
+#
+# Any changes made here will be lost.
+#
+END_HEADER
+
+my @errno_values;
+
+my $max_errno_name_len = 0;
+foreach my $name (sort grep { /^E[A-Z]+$/ } keys %POSIX::) {
+    my $code = POSIX->can($name);
+
+    next unless $code;
+
+    my $value = eval { $code->() };
+
+    next unless defined $value;
+
+    push @errno_values, [ $name, $value ];
+
+    if(length($name) > $max_errno_name_len) {
+        $max_errno_name_len = length($name);
+    }
+}
+
+my $format = ".macro_const POSIX_%-${max_errno_name_len}s %d\n";
+
+foreach my $pair (@errno_values) {
+    my ( $name, $value ) = @$pair;
+
+    printf $format, $name, $value;
+}