[C/C++, OpenACC] Reject vars of different scope in acc declare (PR94120)

[Frederik Harwath]

Tobias Burnus <tobias@codesourcery.com> writes:

Hi Tobias,

> Fortran patch: https://gcc.gnu.org/pipermail/gcc-patches/current/541774.html
>
> "A declare directive must be in the same scope
>   as the declaration of any var that appears in
>   the data clauses of the directive."
>
> ("A declare directive is used […] following a variable
>    declaration in C or C++".)
>
> NOTE for C++: This patch assumes that variables in a namespace
> are handled in the same way as those which are at
> global (namespace) scope; however, the OpenACC specification's
> wording currently is "In C or C++ global scope, only …".
> Hence, one can argue about this part of the patch; but as
> it fixes an ICE and is a very sensible extension – the other
> option is to reject it – I believe it is fine.
> (On the OpenACC side, this is now Issue 288.)

Sounds reasonable to me.

> +bool
> +c_check_oacc_same_scope (tree decl)
> +{
> +  struct c_binding *b = I_SYMBOL_BINDING (DECL_NAME (decl));
> +  return b != NULL && B_IN_CURRENT_SCOPE (b);
> +}

Is the function really specific to OpenACC? If not, then "_oacc"
could be dropped from its name. How about "c_check_current_scope"?

> diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
> index 24f71671469..8f09eb0d375 100644
> --- a/gcc/cp/parser.c
> +++ b/gcc/cp/parser.c
> [...]
> -       if (global_bindings_p ())
> +       if (current_binding_level->kind == sk_namespace)
> [...]
> -  if (error || global_bindings_p ())
> +  if (error || current_binding_level->kind == sk_namespace)
>      return NULL_TREE;

So - just to be sure - the new namespace condition subsumes the old
"global_bindings_p" condition because the global scope is also a namespace,
right? Yes, now I see that you have a test case that demonstrates that
the declare directive still works for global variables with those changes.

> diff --git a/gcc/testsuite/g++.dg/declare-pr94120.C b/gcc/testsuite/g++.dg/declare-pr94120.C
> new file mode 100644
> index 00000000000..8515c4ff875
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/declare-pr94120.C
> @@ -0,0 +1,30 @@
> +/* { dg-do compile }  */
> +
> +/* PR middle-end/94120  */
> +
> +int b[8];
> +#pragma acc declare create (b)

Looks good to me.

Frederik
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