path: root/dh_strip

#!/usr/bin/perl -w

=head1 NAME

dh_strip - strip executables, shared libraries, and some static libraries

=cut

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

=head1 SYNOPSIS

B<dh_strip> [S<I<debhelper options>>] [B<-X>I<item>] [--dbg-package=package] [--keep-debug]

=head1 DESCRIPTION

dh_strip is a debhelper program that is responsible for stripping
executables, shared libraries, and static libraries that are not used for
debugging.

This program examines your package build directories and works out what
to strip on its own. It uses L<file(1)> and file permisions and filenames
to figure out what files are shared libraries (*.so), executable binaries,
and static (lib*.a) and debugging libraries (lib*_g.a, debug/*.so), and
strips each as much as is possible. (Which is not at all for debugging
libraries.) In general it seems to make very good guesses, and will do the
right thing in almost all cases.

Since it is very hard to automatically guess if a file is a
module, and hard to determine how to strip a module, dh_strip does not
currently deal with stripping binary modules such as .o files.

=head1 OPTIONS

=over 4

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

Exclude files that contain "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<--dbg-package=>I<package>

This option tells dh_strip that the given package has an associated "-dbg"
package. dh_strip will, when stripping off the debug symbols of files in
the given package, save them to independent files in the package build
directory for the "-dbg" package.

For example, you might have a package named libfoo, and want to include a
libfoo-dbg package that contains debugging symbols. The command "dh_strip
--dbg-package=libfoo" will make dh_strip save the debugging symbols for
usr/lib/libfoo.so.0 into usr/lib/debug/usr/lib/libfoo.so.0 in the package
build directory for libfoo-dbg. If libfoo-dbg is installed, gdb will
automatically load up the debugging symbols from it when debugging libfoo.

This option may be repeated to list more than one package.

=item B<-k>, B<--keep-debug>

Debug symbols will be retained, but split into an independant
file in usr/lib/debug/ in the package build directory. --dbg-package
is easier to use than this option, but this option is more flexible.

=back

=head1 NOTES

If the DEB_BUILD_OPTIONS environment variable contains "nostrip", nothing
will be stripped, in accordance with Debian policy.

=head1 CONFORMS TO

Debian policy, version 3.0.1

=cut

init();

# This variable can be used to turn off stripping (see Policy).
if (defined $ENV{DEB_BUILD_OPTIONS} && $ENV{DEB_BUILD_OPTIONS} =~ /nostrip/) {
	exit;
}

# I could just use `file $_[0]`, but this is safer
sub get_file_type {
	my $file=shift;
	open (FILE, '-|') # handle all filenames safely
		|| exec('file', $file)
		|| die "can't exec file: $!";
	my $type=<FILE>;
	close FILE;
	return $type;
}

# Check if a file is an elf binary, shared library, or static library,
# for use by File::Find. It'll fill the following 3 arrays with anything
# it finds:
my (@shared_libs, @executables, @static_libs);
sub testfile {
	return if -l $_ or -d $_; # Skip directories and symlinks always.

	# See if we were asked to exclude this file.
	# Note that we have to test on the full filename, including directory.
	my $fn="$File::Find::dir/$_";
	foreach my $f (@{$dh{EXCLUDE}}) {
		return if ($fn=~m/\Q$f\E/);
	}

	# Is it a debug library in a debug subdir?
	return if $fn=~m/debug\/.*\.so/;

	# Does its filename look like a shared library?
	if (m/.*\.so.*?/) {
		# Ok, do the expensive test.
		my $type=get_file_type($_);
		if ($type=~m/.*ELF.*shared.*/) {
			push @shared_libs, $fn;
			return;
		}
	}
	
	# Is it executable? -x isn't good enough, so we need to use stat.
	my (undef,undef,$mode,undef)=stat(_);
	if ($mode & 0111) {
		# Ok, expensive test.
		my $type=get_file_type($_);
		if ($type=~m/.*ELF.*(executable|shared).*/) {
			push @executables, $fn;
			return;
		}
	}
	
	# Is it a static library, and not a debug library?
	if (m/lib.*\.a$/ && ! m/.*_g\.a$/) {
		push @static_libs, $fn;
		return;
	}
}

sub make_debug {
	my $file=shift;
	my $tmp=shift;
	my $desttmp=shift;

	my ($base_file)=$file=~/^\Q$tmp\E(.*)/;
	my $debug_path=$desttmp."/usr/lib/debug/".$base_file;
	my $debug_dir=dirname($debug_path);
	if (! -d $debug_dir) {
		doit("install", "-d", $debug_dir);
	}
	doit("objcopy", "--only-keep-debug", $file, $debug_path);
	# No reason for this to be executable.
	doit("chmod", 644, $debug_path);
	return $debug_path;
}

sub attach_debug {
	my $file=shift;
	my $debug_path=shift;
	doit("objcopy", "--add-gnu-debuglink", $debug_path, $file);
}

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

	# Support for keeping the debugging symbols in a detached file.
	my $keep_debug=$dh{KEEP_DEBUG};
	my $debugtmp=$tmp;
	if (ref $dh{DEBUGPACKAGES} && grep { $_ eq $package } @{$dh{DEBUGPACKAGES}}) {
		$keep_debug=1;
		$debugtmp=tmpdir($package."-dbg");
	}
	
	@shared_libs=@executables=@static_libs=();
	find(\&testfile,$tmp);

	foreach (@shared_libs) {
		my $debug_path = make_debug($_, $tmp, $debugtmp) if $keep_debug;
		# Note that all calls to strip on shared libs
		# *must* inclde the --strip-unneeded.
		doit("strip","--remove-section=.comment",
			"--remove-section=.note","--strip-unneeded",$_);
		attach_debug($_, $debug_path) if $keep_debug;
	}
	
	foreach (@executables) {
		my $debug_path = make_debug($_, $tmp, $debugtmp) if $keep_debug;
		doit("strip","--remove-section=.comment",
			"--remove-section=.note",$_);
 		attach_debug($_, $debug_path) if $keep_debug
	}

	foreach (@static_libs) {
		doit("strip","--strip-debug",$_);
	}
}

=head1 SEE ALSO

L<debhelper(7)>

This program is a part of debhelper.

=head1 AUTHOR

Joey Hess <joeyh@debian.org>

=cut