package ExtUtils::Mkbootstrap;
use Config;
use Exporter;
@ISA=('Exporter');
@EXPORT='&Mkbootstrap';
$Version=2.0; # just to start somewhere

sub Mkbootstrap {

=head1 USEFUL SUBROUTINES

=head2 Mkbootstrap()

Make a bootstrap file for use by this system's DynaLoader.  It
typically gets called from an extension Makefile.

There is no C<*.bs> file supplied with the extension. Instead a
C<*_BS> file which has code for the special cases, like posix for
berkeley db on the NeXT.

This file will get parsed, and produce a maybe empty
C<@DynaLoader::dl_resolve_using> array for the current architecture.
That will be extended by $BSLOADLIBS, which was computed by Andy's
extliblist script. If this array still is empty, we do nothing, else
we write a .bs file with an C<@DynaLoader::dl_resolve_using> array, but
without any C<if>s, because there is no longer a need to deal with
special cases.

The C<*_BS> file can put some code into the generated C<*.bs> file by placing
it in C<$bscode>. This is a handy 'escape' mechanism that may prove
useful in complex situations.

If @DynaLoader::dl_resolve_using contains C<-L*> or C<-l*> entries then
Mkbootstrap will automatically add a dl_findfile() call to the
generated C<*.bs> file.

=cut

    my($baseext, @bsloadlibs)=@_;

    @bsloadlibs = grep($_, @bsloadlibs); # strip empty libs

    print STDOUT "	bsloadlibs=@bsloadlibs\n" if $Verbose;

    # We need DynaLoader here because we and/or the *_BS file may
    # call dl_findfile(). We don't say `use' here because when
    # first building perl extensions the DynaLoader will not have
    # been built when MakeMaker gets first used.
    require DynaLoader;

    rename "$baseext.bs", "$baseext.bso"
      if -s "$baseext.bs";

    if (-f "${baseext}_BS"){
	$_ = "${baseext}_BS";
	package DynaLoader; # execute code as if in DynaLoader
	local($osname, $dlsrc) = (); # avoid warnings
	($osname, $dlsrc) = @Config::Config{qw(osname dlsrc)};
	$bscode = "";
	unshift @INC, ".";
	require $_;
	shift @INC;
    }

    if ($Config{'dlsrc'} =~ /^dl_dld/){
	package DynaLoader;
	push(@dl_resolve_using, dl_findfile('-lc'));
    }

    my(@all) = (@bsloadlibs, @DynaLoader::dl_resolve_using);
    my($method) = '';
    if (@all){
	open BS, ">$baseext.bs"
		or die "Unable to open $baseext.bs: $!";
	print STDOUT "Writing $baseext.bs\n";
	print STDOUT "	containing: @all" if $Verbose;
	print BS "# $baseext DynaLoader bootstrap file for $Config{'osname'} architecture.\n";
	print BS "# Do not edit this file, changes will be lost.\n";
	print BS "# This file was automatically generated by the\n";
	print BS "# Mkbootstrap routine in ExtUtils::Mkbootstrap (v$Version).\n";
	print BS "\@DynaLoader::dl_resolve_using = ";
	# If @all contains names in the form -lxxx or -Lxxx then it's asking for
	# runtime library location so we automatically add a call to dl_findfile()
	if (" @all" =~ m/ -[lLR]/){
	    print BS "  dl_findfile(qw(\n  @all\n  ));\n";
	}else{
	    print BS "  qw(@all);\n";
	}
	# write extra code if *_BS says so
	print BS $DynaLoader::bscode if $DynaLoader::bscode;
	print BS "\n1;\n";
	close BS;
    }
}