Re: [PATCH 1/3] configure: Fix atomic64 test for --enable-werror on macOS

["Alex Bennée" <alex.bennee@linaro.org>]

Thomas Huth <thuth@redhat.com> writes:

> When using --enable-werror for the macOS builders in the Cirrus-CI,
> the atomic64 test is currently failing, and config.log shows a bunch
> of error messages like this:
>
>  config-temp/qemu-conf.c:6:7: error: implicit declaration of function
>  '__atomic_load_8' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
>   y = __atomic_load_8(&x, 0);
>       ^
>  config-temp/qemu-conf.c:6:7: error: this function declaration is not a
>  prototype [-Werror,-Wstrict-prototypes]
>
> Seems like these __atomic_*_8 functions are available in one of the
> libraries there, so that the test links and passes there when not
> using --enable-werror. But there does not seem to be a valid prototype
> for them in any of the header files, so that the test fails when using
> --enable-werror.
>
> Fix it by using the "official" built-in functions instead (see e.g.
> https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html).
> We are not using the *_8 variants in QEMU anyway.
>
> Suggested-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
> Signed-off-by: Thomas Huth <thuth@redhat.com>

This also fixes the failure to set CONFIG_ATOMIC64 for clang (9 and
others) which didn't fail on my box but was certainly missing.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>

-- 
Alex Bennée