#!/usr/bin/perl

=head1 NAME

dh_dwz - optimize DWARF debug information in ELF binaries via dwz

=cut

use strict;
use warnings;
use File::Find;
use Debian::Debhelper::Dh_Lib;

our $VERSION = DH_BUILTIN_VERSION;

=head1 SYNOPSIS

B<dh_dwz> [S<I<debhelper options>>] [B<-X>I<item>] [S<B<--> I<params>>]

=head1 DESCRIPTION

B<Caveat>: This tool is experimental and may disappear or change
behaviour without any notice.

B<dh_dwz> is a debhelper program that will optimize the (uncompressed)
size of the DWARF debug information in ELF binaries.  It does so by
running L<dwz(1)> on all the ELF binaries in the package.

=head1 OPTIONS

=over 4

=item B<-X>I<item>, B<--exclude=>I<item>

Exclude files that contain I<item> anywhere in their filename from being
stripped. You may use this option multiple times to build up a list of
things to exclude.

=item B<--> I<params>

Pass I<params> to L<dwz(1)> when it processes ELF binaries.  This is
mostly useful for setting memory related parameters (e.g. -l and -L).

=back

=head1 NOTES

If the B<DEB_BUILD_OPTIONS> environment variable contains B<nostrip>,
nothing will be stripped, in accordance with Debian policy (section
10.1 "Binaries").

While this tool technically does not remove debug information from
binaries, it is still skipped when the B<DEB_BUILD_OPTIONS>
environment variable contains B<nostrip>.  This is because B<nostrip>
is often used to optimize build times (e.g. for "build and
test"-cycles) rather than optimizing for size.

=cut

init();

# This variable can be used to turn off stripping (see Policy).
exit 0 if get_buildoption('nostrip');

warning('This tool is experimental and may change (or be retired) without any notice');

my @elf_files;

sub testfile {
	my $fn = $_;
	return if -l $fn; # Always skip symlinks.

	# See if we were asked to exclude this file.
	# Note that we have to test on the full filename, including directory.
	if (excludefile($fn)) {
		$File::Find::prune = 1 if -d _;
		return;
	}
	return if -d _;
	# Do not process output files from dwz
	return if index($fn, '/debug/.dwz/') > -1;
	if (is_so_or_exec_elf_file($fn)) {
		push(@elf_files, $fn);
	}
	return;
}

for my $package (@{$dh{DOPACKAGES}}) {
	my $tmp = tmpdir($package);

	next if not -d $tmp;

	@elf_files = ();
	find({
			wanted => \&testfile,
			no_chdir => 1,
		 }, $tmp);
	next if not @elf_files;
	# Consistent order;
	@elf_files = sort(@elf_files);
	my ($unique_files, $hardlinks) = find_hardlinks(@elf_files);

	# TODO: Support multifile (-m)

	xargs($unique_files, 'dwz', '-q', @{$dh{U_PARAMS}}, '--');
	# Now change over any files we can that used to be hard links so
	# they are again.
	for my $hardlink (keys %{$hardlinks}) {
		my $target = $hardlinks->{$hardlink};
		# Remove old file.
		rm_files($hardlink);
		# Make new hardlink.
		doit('ln', '-f', $target, $hardlink);
	}
}

=head1 SEE ALSO

L<debhelper(7)>

This program is a part of debhelper.

=head1 AUTHOR

Niels Thykier <niels@thykier.net>

=cut