[Spice-devel] [vdagent-linux] Add -fno-strict-aliasing to default CFLAGS

[Fabiano Fidencio]

----- Original Message -----
> From: "Christophe Fergeau" <cfergeau at redhat.com>
> To: spice-devel at freedesktop.org
> Sent: Monday, June 15, 2015 4:31:44 PM
> Subject: [Spice-devel] [vdagent-linux] Add -fno-strict-aliasing to default	CFLAGS
> 
> Compilation breaks with older gcc versions (gcc (GCC) 4.4.7 20120313
> (Red Hat 4.4.7-11) on RHEL6) with the following error (due to the
> additional use of -Werror in the default CFLAGS)
> CC     src/src_spice_vdagent-vdagent-x11-randr.o
> cc1: warnings being treated as errors
> src/vdagent-x11-randr.c: In function ‘vdagent_x11_randr_handle_event’:
> src/vdagent-x11-randr.c:499: error: dereferencing pointer ‘sce’ does break
> strict-aliasing rules
> src/vdagent-x11-randr.c:499: error: dereferencing pointer ‘sce’ does break
> strict-aliasing rules
> src/vdagent-x11-randr.c:498: note: initialized from here
> make: *** [src/src_spice_vdagent-vdagent-x11-randr.o] Error 1
> 
> Strict aliasing is not something we must have for the agent, and the
> alternative would most likely involve an anonymous union, or some
> casting. Given that this warning only occurs with these older compilers,
> better to go with a fix as non-invasive as possible.
> 
> Resolves: https://bugs.freedesktop.org/show_bug.cgi?id=90981
> ---
>  configure.ac | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/configure.ac b/configure.ac
> index f559c2e..ca9a15b 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -130,7 +130,7 @@ fi
>  
>  # If no CFLAGS are set, set some sane default CFLAGS
>  if test "$ac_test_CFLAGS" != set; then
> -  DEFAULT_CFLAGS="-Wall -Werror -Wp,-D_FORTIFY_SOURCE=2 -fstack-protector
> --param=ssp-buffer-size=4"
> +  DEFAULT_CFLAGS="-Wall -Werror -Wp,-D_FORTIFY_SOURCE=2 -fno-strict-aliasing
> -fstack-protector --param=ssp-buffer-size=4"
>    for F in $DEFAULT_CFLAGS; do
>      AC_MSG_CHECKING([whether $CC supports $F])
>      save_CFLAGS="$CFLAGS"
> --
> 2.4.3
> 
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> 

ACK!