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Date: Tue, 10 Mar 2015 13:12:11 -0400
From: John Snow <jsnow@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 2/2] configure: silence glib unknown
 attribute __alloc_size__
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To: Stefan Hajnoczi <stefanha@redhat.com>, qemu-devel@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>, Peter Maydell <peter.maydell@linaro.org>, Stefan Weil <sw@weilnetz.de>



On 03/10/2015 08:23 AM, Stefan Hajnoczi wrote:
> The glib headers use GCC attributes.  Unfortunately the __GNUC__ and
> __GNUC_MINOR__ version macros are also defined by clang, but clang
> doesn't support the same attributes as GCC.
>
> clang 3.5.0 does not support the __alloc_size__ attribute:
>
>    https://github.com/llvm-mirror/clang/commit/c047507a9a79e89fc8339e074fa72822a7e7ea73
>
> The following warning is produced:
>
>    gstrfuncs.h:257:44: warning: unknown attribute '__alloc_size__' ignored [-Wunknown-attributes]
>        G_GNUC_MALLOC G_GNUC_ALLOC_SIZE(2);
>    gmacros.h:67:45: note: expanded from macro 'G_GNUC_ALLOC_SIZE'
>        #define G_GNUC_ALLOC_SIZE(x) __attribute__((__alloc_size__(x)))
>
> This patch checks whether glib headers cause warnings and disables
> -Wunknown-attributes if that is the case.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>   configure | 10 ++++++++++
>   1 file changed, 10 insertions(+)
>
> diff --git a/configure b/configure
> index 4f9f689..00740ad 100755
> --- a/configure
> +++ b/configure
> @@ -2773,6 +2773,16 @@ if ! $pkg_config --atleast-version=2.38 glib-2.0; then
>       glib_subprocess=no
>   fi
>
> +# Silence clang 3.5.0 warnings about glib attribute __alloc_size__ usage
> +cat > $TMPC << EOF
> +#include <glib.h>
> +int main(void) { return 0; }
> +EOF
> +if ! compile_prog "-Werror" "" ; then
> +  glib_cflags="-Wno-unknown-attributes $glib_cflags"
> +  CFLAGS="-Wno-unknown-attributes $CFLAGS"
> +fi
> +
>   ##########################################
>   # SHA command probe for modules
>   if test "$modules" = yes; then
>

Reviewed-by: John Snow <jsnow@redhat.com>