On 08/22/2014 05:05 AM, Stefan Hajnoczi wrote:
On Fri, Aug 22, 2014 at 9:20 AM, Daniel P. Berrange <berra...@redhat.com> wrote:
On Thu, Aug 21, 2014 at 08:10:54PM -0400, John Snow wrote:
I was running a series of tests on 32 and 64 bit hosts to test for
endianness and variable width issues when I noticed that I couldn't properly
perform a build of "make check" against a 32bit target from a 64bit host:
../../configure --cpu=i386 && make -j4 && make check
This produces some warnings in tests-cutils about overflowing variables that
are of type guint64. It's been mentioned on the mailing lists before,
actually: http://lists.gnu.org/archive/html/qemu-devel/2014-05/msg00452.html
The problem is that guint64 is being aliased against "unsigned long", which
is only 4 bytes instead of the implied 8. This occurs because we link
against the 64bit headers for glib instead of the 32bit ones when we're
building for i386 from an x86_64 host.
Our include flags wind up looking like: -I/usr/include/glib-2.0 but
-I/usr/lib64/glib-2.0/include
I was discussing the problem with Stefan:
On 08/21/2014 05:03 AM, Stefan Hajnoczi wrote:
The problem is that pkg-config uses libdir=/usr/lib64 by default on
amd64 hosts. It doesn't know that gcc -m32 is being used.
This results in glib's 64-bit headers being used where guint64 is just
unsigned long. On 32-bit hosts this is incorrect.
Two workarounds:
1. yum install pkgconfig.i686 and run it instead of pkgconfig.x86_64
2. Use the pkg-config --define-variable libdir=/usr/lib option
You can set PKG_CONFIG=path/to/pkg-config.i686 on QEMU's ./configure
command-line.
This is all distro-specific :(. Any other solutions?
Stefan
I am not extremely well versed in configure or pkg-config ninjutsu, but I
must imagine that the ARCH/cpu variables we are setting in configure could
help us know to call the 32bit pkg-config instead of the native 64bit
version and fix this issue.
Does anyone have any good ideas? Surely other projects must have run into
this elsewhere.
Distros will install pkg-config .pc files for non-native architectures
in a different location normally. The supported / recommended way to
tell pkg-config to look in these alternative dirs is to set the env
variable PKG_CONFIG_LIBDIR. This replaces the built-in default search
directory that looks for native.
So on a Fedora / RHELL system, to make pkg-config use 32-bit libs you
want to set
PKG_CONFIG_LIBDIR=/usr/lib/pkgconfig
which replaces the default location of /usr/lib64/pkgconfig.
Nice, and Paolo sent me an automated way of doing that:
On Fri, Aug 22, 2014 at 12:14:28AM +0200, Paolo Bonzini wrote:
You need to set PKG_CONFIG_LIBDIR to
/usr/lib/$MULTILIBDIR/pkgconfig
where MULTILIBDIR is
if $CC -print-multiarch >/dev/null 2>&1; then
MULTILIBDIR=`$CC -print-multiarch $CFLAGS $CPPFLAGS`
fi
if test -z "$MULTILIBDIR"; then
MULTILIBDIR=`$CC --print-multi-os-directory $CFLAGS $CPPFLAGS`
fi
This will point at /usr/lib/pkgconfig/glib-2.0.pc instead of
/usr/lib64/pkgconfig/glib-2.0.pc
I tested that it works.
Stefan
A barrier into introducing this into the configuration script is that
clang, used on OSX hosts, does not support these print flags.
Even worse, clang --print-multi-os-directory produces "x86_64" on Fedora
20, which will lead to an erroneous configuration.
So we'll have to look into another way to support cross-compilation for
i386 on x86_64 to avoid script breakage on other platforms.
Any other ideas? It looks as if there have been proposals in the past to
add some multi-arch awareness into pkg-config, but they haven't gone
anywhere. So some tool needs to tell pkg-config where to look, but clang
is apparently not up to the job.
Where does gcc/g++ find out about the lib directories? Or are they
baked-in per distro?
Any ideas?
--j
