Re: [C PATCH] Prevent -Wunused-value warning with __atomic_fetch_* (PR c/69407)

[Marek Polacek <polacek at redhat dot com>]

Ping.

On Fri, Mar 04, 2016 at 07:03:09PM +0100, Marek Polacek wrote:
> On Fri, Mar 04, 2016 at 06:41:26PM +0100, Jakub Jelinek wrote:
> > I'm ok with it for gcc6.
> 
> Cool.
> 
> > But IMHO you should add dg-bogus directives here.
> 
> Ok, version with dg-bogus:
> 
> Bootstrapped/regtested on x86_64-linux, ok for trunk?
> 
> 2016-03-04  Marek Polacek  <polacek@redhat.com>
> 
> 	PR c/69407
> 	* c-common.c (resolve_overloaded_builtin): Set TREE_USED for the fetch
> 	operations.
> 
> 	* gcc.dg/atomic-op-6.c: New test.
> 
> diff --git gcc/c-family/c-common.c gcc/c-family/c-common.c
> index 965cf49..25afa9c 100644
> --- gcc/c-family/c-common.c
> +++ gcc/c-family/c-common.c
> @@ -11443,6 +11443,10 @@ resolve_overloaded_builtin (location_t loc, tree function,
>  	    && orig_code != BUILT_IN_ATOMIC_STORE_N)
>  	  result = sync_resolve_return (first_param, result, orig_format);
>  
> +	if (fetch_op)
> +	  /* Prevent -Wunused-value warning.  */
> +	  TREE_USED (result) = true;
> +
>  	/* If new_return is set, assign function to that expr and cast the
>  	   result to void since the generic interface returned void.  */
>  	if (new_return)
> diff --git gcc/testsuite/gcc.dg/atomic-op-6.c gcc/testsuite/gcc.dg/atomic-op-6.c
> index e69de29..f88c293 100644
> --- gcc/testsuite/gcc.dg/atomic-op-6.c
> +++ gcc/testsuite/gcc.dg/atomic-op-6.c
> @@ -0,0 +1,11 @@
> +/* Test we don't generate bogus warnings.  */
> +/* PR c/69407 */
> +/* { dg-do compile } */
> +/* { dg-options "-Wall -Wextra" } */
> +
> +void
> +foo (int *p, int a)
> +{
> +  __atomic_fetch_add (&p, a, 0); /* { dg-bogus "value computed is not used" } */
> +  __atomic_add_fetch (&p, a, 0); /* { dg-bogus "value computed is not used" } */
> +}

	Marek