[C++ PATCH] Fix delayed folding -Wnonnull regression (PR c++/86210)

[Jason Merrill]

On Wed, Jun 20, 2018 at 10:32 AM, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> This patch fixes a regression caused by C++ delayed folding, when
> check_nonnull_arg is called, the arguments aren't folded yet and so unlike
> GCC 4.8 and earlier we don't report -Wnonnull warning unless the argument is
> literal NULL without any folding.
>
> Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
> trunk?  Is this something we should backport (at least to 8.2) or not?

OK for trunk and 8.2.

> 2018-06-20  Jakub Jelinek  <jakub@redhat.com>
>
>         PR c++/86210
>         * c-common.c (check_nonnull_arg): Use fold_for_warn.  Adjust obsolete
>         comment.
>
>         * g++.dg/warn/Wnonnull4.C: New test.
>
> --- gcc/c-family/c-common.c.jj  2018-06-20 08:15:20.697849713 +0200
> +++ gcc/c-family/c-common.c     2018-06-20 12:14:27.828098317 +0200
> @@ -5404,10 +5404,8 @@ check_nonnull_arg (void *ctx, tree param
>    if (TREE_CODE (TREE_TYPE (param)) != POINTER_TYPE)
>      return;
>
> -  /* When not optimizing diagnose the simple cases of null arguments.
> -     When optimization is enabled defer the checking until expansion
> -     when more cases can be detected.  */
> -  if (integer_zerop (param))
> +  /* Diagnose the simple cases of null arguments.  */
> +  if (integer_zerop (fold_for_warn (param)))
>      {
>        warning_at (pctx->loc, OPT_Wnonnull, "null argument where non-null "
>                   "required (argument %lu)", (unsigned long) param_num);
> --- gcc/testsuite/g++.dg/warn/Wnonnull4.C.jj    2018-06-20 12:21:50.424552232 +0200
> +++ gcc/testsuite/g++.dg/warn/Wnonnull4.C       2018-06-20 12:20:47.356487553 +0200
> @@ -0,0 +1,21 @@
> +// PR c++/86210
> +// { dg-do compile }
> +// { dg-options "-Wnonnull" }
> +
> +void *declared_not_defined (void *p) __attribute__((nonnull));
> +
> +inline void *declared_and_defined (void *p) __attribute__((nonnull));
> +
> +int
> +main ()
> +{
> +  int *const p = 0;
> +  declared_not_defined (p);    // { dg-warning "null argument where non-null required" }
> +  declared_and_defined (p);    // { dg-warning "null argument where non-null required" }
> +}
> +
> +void *
> +declared_and_defined (void *p)
> +{
> +  return p;
> +}
>
>         Jakub