Re: [igt-dev] [PATCH i-g-t v2 1/4] meson: add libatomic dependency

["Ser, Simon" <simon.ser@intel.com>]

On Thu, 2019-06-13 at 14:53 +0100, Guillaume Tucker wrote:
> Add conditional dependency on libatomic in order to be able to use the
> __atomic_* functions instead of the older __sync_* ones.  The
> libatomic library is only needed when there aren't any native support
> on the current architecture, so a linker test is used for this
> purpose.  This enables atomic operations to be on a wider number of
> architectures including MIPS.
> 
> Signed-off-by: Guillaume Tucker <guillaume.tucker@collabora.com>
> ---
>  meson.build | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/meson.build b/meson.build
> index 6268c58d3634..da25a28f3268 100644
> --- a/meson.build
> +++ b/meson.build
> @@ -179,6 +179,19 @@ math = cc.find_library('m')
>  realtime = cc.find_library('rt')
>  dlsym = cc.find_library('dl')
>  zlib = cc.find_library('z')
> +if cc.links('''
> +#include <stdint.h>
> +int main(void) {
> +  uint32_t x32 = 0;
> +  uint64_t x64 = 0;
> +  __atomic_load_n(&x32, __ATOMIC_SEQ_CST);
> +  __atomic_load_n(&x64, __ATOMIC_SEQ_CST);

Minor: maybe we could've used stdatomic.h's atomic_* functions (without
the "__" prefix) for consistency with the actual IGT code?

> +  return 0;
> +}''', name : 'built-in atomics')
> +	libatomic = []

We could use null_dep instead, to make it consistent with the other
branch.

> +else
> +	libatomic = cc.find_library('atomic')
> +endif
>  
>  if cc.has_header('linux/kd.h')
>  	config.set('HAVE_LINUX_KD_H', 1)
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