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dpkg-cross proposals (was: How to handle cross compiling source packages?)

Dear dpkg-cross Developers,

Here are some proposals to fix the problems I mentioned my last mail.


1. small bugfix in DEB_* environment variables
----------------------------------------------

    While stepping through the sources, I found a nasty typo.
    It causes the DPKG_* environment variables not to be set
    correctly.

    This is fixed by:
        patch-dpkgcross-fix-DEB-variables.diff


2. use /etc/dpkg-cross/cross-config.$(DEB_HOST_ARCH_OS)
-------------------------------------------------------

    The files cross-config.* contain a suffix for each architecture.
    Some suffixes are CPU type, but most are OS types.

    I don't think it was initially indenteded to use $arch or
    $(DEB_HOST_ARCH), e.g. "hurd-i386" as suffix. Looking at the
    documentation and source comments, it seems to me that the authors
    meant $(DEB_HOST_ARCH_OS) instead, e.g. "hurd".

    If I got it right, the system is intended to do the following:
    dpkg-cross.pl includes the cross-config.OS which includes
    the cross-config.common which includes the cross-config.CPU

    Otherwise, there would have to exist a file cross-config.hurd-i386
    which of course isn't there.


    This is fixed by:
        patch-dpkgcross-use-DEB_HOST_ARCH_OS.diff


3. use dpkg-architecture instead of %archtable
----------------------------------------------

    dpkg-cross uses an internal table %archtable for mapping $arch
    to the GNU type.  (e.g.  i386 -> i486-linux-gnu)
    However, dpkg-architecture does the job much better.

    This has already been marked in the dpkg-cross.pl:
        # FIXME: should use dpkg-architecture here

    But there's a subtle circular dependency. When cross compiling
    a package using "dpkg-buildpackage -a...", it results in an
    infinite recursion. It was hard to analyze it, here's a simplified
    summary of my research:

        * dpkg-buildpackage sets gcc -> gccross
        * dpkg-buildpackage calls (indirectly) gcc

        Loop:
        * gcc has been mapped to gccross
        * gccross includes dpkg-cross.pl
        * dpkg-cross.pl calls dpkg-architecture
        * dpkg-architecture calls gcc
        * gcc has been mapped to gccross
        * ...

    This is really stupid. dpkg-architecture rather doesn't need
    to call "gcc", because dpkg-cross.pl doesn't asks for the
    current architecture.

    Since dpkg-architecture only needs programs in /usr/bin, that
    problem can be solved by setting PATH=/usr/bin before calling
    dpkg-architecture.

    This is fixed by:
        patch-dpkgcross-use-dpkg-architecture.diff


4. modifying the PATH correctly
-------------------------------

    dpkg-cross.pl changes the PATH:
        $ENV{'PATH'} = "/usr/share/dpkg-cross:$ENV{PATH}:$crossbin";

    However, when there's e.g. SDL installed, the sdl-config of /usr/bin
    would be used, instead of the correct $crossbin/sdl-config. So the
    $crossbin should take precendence:
        $ENV{'PATH'} = "/usr/share/dpkg-cross:$crossbin:$ENV{PATH}";

    In addition, the "strip" wrapper doesn't work for me, and the
    wrong "ranlib" is called. (which isn't patform independent!)

    So the only way I currently get it working is by putting $crossbin
    at the first place of PATH:
        $ENV{'PATH'} = "$crossbin:/usr/share/dpkg-cross:$ENV{PATH}";


    However, on the other hand, the sources contain a comment which
    states that they "append $crossbin, so that cross binaries can
    be found, but native stuff still has precedence (if a package
    wants to compile with 'gcc' a build tool that will be executed,
    for example)."


    This is a serious problem. Maybe I could bugfix the wrappers and
    include "ar" and "ranlib" in %std_tools. This way cross compiling
    would generally work with $crossbin as the last PATH entry. But
    what's about sdl-config, pkg-config, etc.?


    I don't supply a patch, because I'm unsure how to solve that
    problem. Does anyone use dpkg-cross to build applications that
    use glib-config, gtk-config, sdl-config or similar?



Greets,

    Volker

-- 
Volker Grabsch
---<<(())>>---
Administrator
NotJustHosting GbR

Wed Apr 12 13:02:17 CEST 2006  Volker Grabsch <vog@notjusthosting.com>
  * fix-DEB-variables
diff -rN -u old-dpkg-cross/dpkg-cross-1.26/dpkg-cross.pl new-dpkg-cross/dpkg-cross-1.26/dpkg-cross.pl
--- old-dpkg-cross/dpkg-cross-1.26/dpkg-cross.pl	2006-04-12 13:04:21.000000000 +0200
+++ new-dpkg-cross/dpkg-cross-1.26/dpkg-cross.pl	2006-04-12 13:04:21.000000000 +0200
@@ -459,7 +459,7 @@
 	# Set `dpkg-architecture' environment veriables.
 	foreach $var_ qw(DEB_HOST_ARCH DEB_HOST_ARCH_OS DEB_HOST_ARCH_CPU
         		DEB_HOST_GNU_CPU DEB_HOST_GNU_SYSTEM DEB_HOST_GNU_TYPE) {
-		chomp ($tmp = `dpkg-architecture -a$arch -q$var_ 2>/dev/null`);
+		chomp ($tmp_ = `dpkg-architecture -a$arch -q$var_ 2>/dev/null`);
 		$ENV{$var_} = $tmp_;
 	}
 	


Wed Apr 12 13:08:41 CEST 2006  Volker Grabsch <vog@notjusthosting.com>
  * use-DEB_HOST_ARCH_OS
diff -rN -u old-dpkg-cross/dpkg-cross-1.26/dpkg-cross.pl new-dpkg-cross/dpkg-cross-1.26/dpkg-cross.pl
--- old-dpkg-cross/dpkg-cross-1.26/dpkg-cross.pl	2006-04-12 14:19:24.000000000 +0200
+++ new-dpkg-cross/dpkg-cross-1.26/dpkg-cross.pl	2006-04-12 14:19:24.000000000 +0200
@@ -475,9 +475,9 @@
 	# Set USRLIBDIR to $(CROSSLIB), for imake-generated Makefiles..
 	$makeflags_{'USRLIBDIR'} = $crosslib;
 	
-	# Set CONFIG_SITE to /etc/dpkg-cross/cross-config.``$arch'', for
+	# Set CONFIG_SITE to /etc/dpkg-cross/cross-config.``$(DEB_HOST_ARCH_OS)'', for
 	# packages using GNU autoconf configure scripts.
-	$makeflags_{'CONFIG_SITE'} = "/etc/dpkg-cross/cross-config.$arch";
+	$makeflags_{'CONFIG_SITE'} = "/etc/dpkg-cross/cross-config.$ENV{'DEB_HOST_ARCH_OS'}";
 	
 	# Set standard variables for compilers and binutils.
 	foreach $var_ ( keys %std_tools ) {


Wed Apr 12 19:34:14 CEST 2006  Volker Grabsch <vog@notjusthosting.com>
  * use-dpkg-architecture
diff -rN -u old-dpkg-cross/dpkg-cross-1.26/dpkg-cross.pl new-dpkg-cross/dpkg-cross-1.26/dpkg-cross.pl
--- old-dpkg-cross/dpkg-cross-1.26/dpkg-cross.pl	2006-04-12 19:35:22.000000000 +0200
+++ new-dpkg-cross/dpkg-cross-1.26/dpkg-cross.pl	2006-04-12 19:35:22.000000000 +0200
@@ -261,7 +261,13 @@
 	# Set ``$arch'' to defaults if not already specified.
 	$arch = get_architecture();
 	die "$progname: Architecture is not specified.\n" unless ($arch);
-	$deb_host_gnu_type = $archtable{$arch};		# FIXME: should use dpkg-architecture here
+	
+	# Get the DEB_HOST_GNU_TYPE from dpkg-architecture.
+	# The PATH is set to /usr/bin to avoid infinite recursion.
+	# This may be caused by dpkg-architecture calling gccross,
+	# thinking it calls gcc. So we ensure that dpkg-architecture
+	# to always calls /usr/bin/gcc.
+	chomp ($deb_host_gnu_type = `PATH=/usr/bin dpkg-architecture -a$arch -qDEB_HOST_GNU_TYPE 2>/dev/null`);
 	
 	# Finalize, no subst possible crossbase.
 	$crossbase ||= "/usr";
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