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

[Peter Maydell <peter.maydell@linaro.org>]

On 13 November 2015 at 11:31, 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.
>
> 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>

I just noticed this never got applied to master -- did it just fall through
the cracks, or is there an issue with it?

thanks
-- PMM