Re: [Qemu-devel] [PATCH v2] configure: sanity check the glib library that pkg-config finds

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Daniel P. Berrange (berrange@redhat.com) wrote:
> Developers on 64-bit machines will often try to perform a
> 32-bit build of QEMU by running
> 
>   ./configure --extra-cflags="-m32"
> 
> Unfortunately if PKG_CONFIG_LIBDIR is not set to point to
> the location of the 32-bit pkg-config files, then configure
> will silently pick up the 64-bit pkg-config files and still
> succeed.

Having fallen into this trap, thanks; seems to do the trick on RHEL7.x:


# /root/try/../qemu/configure --prefix=/root/try  --enable-trace-backends=stderr --extra-cflags="-m32" --extra-ldflags="-m32"

ERROR: sizeof(size_t) doesn't match GLIB_SIZEOF_SIZE_T.
       You probably need to set PKG_CONFIG_LIBDIR
       to point to the right pkg-config files for your
       build target

# export PKG_CONFIG_LIBDIR=/usr/lib/pkgconfig
# /root/try/../qemu/configure --prefix=/root/try  --enable-trace-backends=stderr --extra-cflags="-m32" --extra-ldflags="-m32"
Install prefix    /root/try
BIOS directory    /root/try/share/qemu
....

and the gsize def ( https://developer.gnome.org/glib/stable/glib-Basic-Types.html#gsize )
does say it should always match size_t size.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Dave

> 
> This causes a problem for glib because it means QEMU will
> be pulling in /usr/lib64/glib-2.0/include/glibconfig.h
> instead of /usr/lib/glib-2.0/include/glibconfig.h
> 
> This causes problems because the 'gsize' type (defined as
> 'unsigned long') will no longer be fully compatible with
> the 'size_t' type (defined as 'unsigned int'). Although
> both are the same size, the compiler refuses to allow
> casts from 'unsigned long *' to 'unsigned int *' as they
> are different pointer types. This results in non-obvious
> compiler errors when building QEMU eg
> 
> qga/commands-posix.c: In function ‘qmp_guest_set_user_password’:
> qga/commands-posix.c:1912:55: error: passing argument 2 of ‘g_base64_decode’ from incompatible pointer type [-Werror=incompatible-pointer-types]
>      rawpasswddata = (char *)g_base64_decode(password, &rawpasswdlen);
>                                                             ^
> In file included from /usr/include/glib-2.0/glib.h:35:0,
>                  from qga/commands-posix.c:14:
> /usr/include/glib-2.0/glib/gbase64.h:52:9: note: expected ‘gsize * {aka long unsigned int *}’ but argument is of type ‘size_t * {aka unsigned int *}’
>  guchar *g_base64_decode         (const gchar  *text,
>          ^
> cc1: all warnings being treated as errors
> 
> To detect this problem, add a check to configure that
> verifies that GLIB_SIZEOF_SIZE_T matches sizeof(size_t).
> If this fails print a warning suggesting that the dev
> probably needs to set PKG_CONFIG_LIBDIR.
> 
> On Fedora x86_64 it passes with any of:
> 
>  # ./configure
>  # PKG_CONFIG_LIBDIR=/usr/lib/pkgconfig ./configure --extra-cflags="-m32"
>  # PKG_CONFIG_LIBDIR=/usr/lib64/pkgconfig ./configure --extra-cflags="-m64"
> 
> And fails with a mis-match
> 
>  # PKG_CONFIG_LIBDIR=/usr/lib64/pkgconfig ./configure --extra-cflags="-m32"
>  # PKG_CONFIG_LIBDIR=/usr/lib/pkgconfig ./configure --extra-cflags="-m64"
> 
> ERROR: sizeof(size_t) doesn't match GLIB_SIZEOF_SIZE_T.
>        You probably need to set PKG_CONFIG_LIBDIR
>        to point to the right pkg-config files for your
>        build target
> 
> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> ---
> Changed in v2:
> 
>  - Add 'return 0' to silence compiler warning on some
>    platforms about returning without a value
> 
>  configure | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/configure b/configure
> index f75df4b..c53334f 100755
> --- a/configure
> +++ b/configure
> @@ -2939,6 +2939,27 @@ for i in $glib_modules; do
>      fi
>  done
>  
> +# Sanity check that the current size_t matches the
> +# size that glib thinks it should be. This catches
> +# problems on multi-arch where people try to build
> +# 32-bit QEMU while pointing at 64-bit glib headers
> +cat > $TMPC <<EOF
> +#include <glib.h>
> +#include <unistd.h>
> +
> +int main(void) {
> +   G_STATIC_ASSERT(sizeof(size_t) == GLIB_SIZEOF_SIZE_T);
> +   return 0;
> +}
> +EOF
> +
> +if ! compile_prog "-Werror $CFLAGS" "$LIBS" ; then
> +    error_exit "sizeof(size_t) doesn't match GLIB_SIZEOF_SIZE_T."\
> +               "You probably need to set PKG_CONFIG_LIBDIR"\
> +	       "to point to the right pkg-config files for your"\
> +	       "build target"
> +fi
> +
>  # g_test_trap_subprocess added in 2.38. Used by some tests.
>  glib_subprocess=yes
>  if ! $pkg_config --atleast-version=2.38 glib-2.0; then
> -- 
> 2.5.0
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK