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#!/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<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<--dwz-multifile>, B<--no-dwz-multifile>
Whether L<dwz(1)> should generate a I<multifile> from the ELF binaries
in the same package. When enabled, if a package ships at least 2 ELF
binaries, B<dh_dwz> will instruct L<dwz(1)> to generate a multifile
for the package.
By default, B<dh_dwz> will attempt to create a multifile but will
continue without if L<dwz(1)> does not create one (but succeeds anyway).
This commonly happens when the debug files do not contain debug
symbols (e.g. a missing -g to the compiler) or when the debug
symbols are compressed (see Debian bug #931891). If B<--dwz-multifile>
is passed, then B<dh_dwz> will abort with an error if L<dwz(1)> does
not create a multifile.
Note this options may not work if a package contains more ELF binaries
than can fit on a single command line. If this becomes a problem,
please pass B<--no-dwz-multifile> to work around the issue.
The generated multifile will be compressed with B<objcopy
--compress-debug-sections>.
Note for B<udeb> packages: B<dh_dwz> will never generate multifiles
for B<udeb> packages. It will still use B<dwz> to reduce the
file size of debug files if it finds any.
=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
my $create_multifile = 'auto';
init(options => {
'dwz-multifile!' => \$create_multifile,
});
# This variable can be used to turn off stripping (see Policy).
exit 0 if get_buildoption('nostrip');
if (not has_tool('dwz')) {
warning("Assuming bootstrap scenario and skipping regular dh_dwz feature, since dwz is not in PATH!");
exit 0;
}
my @elf_files;
sub has_tool {
my ($cmd) = @_;
for my $p (split(m/:/, $ENV{PATH})) {
return 1 if -f -x "${p}/${cmd}";
}
return 0;
}
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, $fn);
}
return;
}
on_items_in_parallel(\@{$dh{DOPACKAGES}}, sub {
foreach my $package (@_) {
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, $hardlinks) = find_hardlinks(@elf_files);
if ($create_multifile and @{$unique_files} > 1 and not is_udeb($package)) {
my $objcopy = cross_command($package, 'objcopy');
my $ma_dir = dpkg_architecture_value('DEB_HOST_MULTIARCH');
my $dwz_dir = "usr/lib/debug/.dwz/${ma_dir}";
my $m = "${dwz_dir}/${package}.debug";
my @dwz_options = ("-m${tmp}/${m}", "-M/${m}");
install_dir("${tmp}/${dwz_dir}");
doit('dwz', @dwz_options, @{$dh{U_PARAMS}}, '--', @{$unique_files});
if ( -f "${tmp}/${m}") {
doit($objcopy, '--compress-debug-sections', "${tmp}/${m}");
reset_perm_and_owner(0644, "${tmp}/${m}");
} else {
error("dwz failed to create a multifile as requested") if $create_multifile ne 'auto';
warning("No dwz multifile created, but not explicitly requested either so ignoring it.");
warning("Common issues include no debug information at all (missing -g) and");
warning("compressed debug information (#931891).");
# Clean up after ourselves to avoid leaving empty directories in packages
doit('rmdir', '-p', '--ignore-fail-on-non-empty', "${tmp}/${dwz_dir}");
}
} else {
xargs($unique_files, 'dwz', @{$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
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