Re: [Qemu-devel] [PATCH] Fix compilation on GCC 4.5

[Stefan Weil <sw@weilnetz.de>]

Am 03.10.2012 20:04, schrieb Søren Sandmann:
> From: Søren Sandmann Pedersen<ssp@redhat.com>
>
> Apparently GCC 4.5 still warns about "value computed not used" even
> with __attribute__((unused)). Fix this by only doing the compile time
> check on gcc>  4.5.
>
> Signed-off-by: Soren Sandmann<ssp@redhat.com>
> ---
>
> I need this patch to get qemu to compile with GCC 4.5, but I'm not
> sure if 4.5 is the right compiler version to check against.
>
>   osdep.h |    5 +++--
>   1 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/osdep.h b/osdep.h
> index cb213e0..df89552 100644
> --- a/osdep.h
> +++ b/osdep.h
> @@ -41,8 +41,9 @@ typedef signed int              int_fast16_t;
>   #endif
>
>   /* Convert from a base type to a parent type, with compile time checking.  */
> -#ifdef __GNUC__
> -#define DO_UPCAST(type, field, dev) ( __extension__ ( { \
> +#if defined (__GNUC__)&&  \
> +    (__GNUC__>  4 || (__GNUC__ == 4&&  __GNUC_MINOR__>  5))
> +#define DO_UPCAST(type, field, dev) ( __extension__ ( {	\
>       char __attribute__((unused)) offset_must_be_zero[ \
>           -offsetof(type, field)]; \
>       container_of(dev, type, field);}))

Hello,

I don't see any warnings with gcc Debian 4.4.5-8.

Could you please provide more information on your environment
and the warnings which you get?

Here is a macro which simplifies the version check:

#if QEMU_GNUC_PREREQ(4, 6)

Regards

Stefan Weil