Re: PATCH to fix bogus -Wimplicit-fallthrough warning (PR c++/77803)

[Marek Polacek <polacek at redhat dot com>]

Ping.

On Sat, Oct 01, 2016 at 04:17:22PM +0200, Marek Polacek wrote:
> On Sat, Oct 01, 2016 at 07:17:50AM +0200, Markus Trippelsdorf wrote:
> > On 2016.09.30 at 23:31 +0200, Marek Polacek wrote:
> > > This PR reports a bogus -Wimplicit-fallthrough warning on the attached test.
> > > The problem is that last_stmt_in_scope should for GIMPLE_TRY, if the last
> > > statement of the eval part can't fallthrough, return this statement and don't
> > > warn.  And the same should be true for FALLTHROUGH ().   This patch fixes it.
> > > 
> > > Bootstrapped/regtested on x86_64-linux, ok for trunk?
> > 
> > Try to compile the testcase without the fallthrough attribute...
> 
> Nuts.  Forgot that gimple_call_internal_p doesn't handle NULL.
> 
> Bootstrapped/regtested on x86_64-linux and ppc64-linux, ok for trunk?
> 
> 2016-10-01  Marek Polacek  <polacek@redhat.com>
> 
> 	PR c++/77803
> 	* gimplify.c (last_stmt_in_scope): Add check for FALLTHROUGH ().
> 
> 	* g++.dg/warn/Wimplicit-fallthrough-1.C: New test.
> 
> diff --git gcc/gimplify.c gcc/gimplify.c
> index 66bb8be..a60d947 100644
> --- gcc/gimplify.c
> +++ gcc/gimplify.c
> @@ -1687,6 +1687,8 @@ last_stmt_in_scope (gimple *stmt)
>  	stmt = gimple_seq_last_stmt (gimple_try_eval (try_stmt));
>  	gimple *last_eval = last_stmt_in_scope (stmt);
>  	if (gimple_stmt_may_fallthru (last_eval)
> +	    && (last_eval == NULL
> +		|| !gimple_call_internal_p (last_eval, IFN_FALLTHROUGH))
>  	    && gimple_try_kind (try_stmt) == GIMPLE_TRY_FINALLY)
>  	  {
>  	    stmt = gimple_seq_last_stmt (gimple_try_cleanup (try_stmt));
> diff --git gcc/testsuite/g++.dg/warn/Wimplicit-fallthrough-1.C gcc/testsuite/g++.dg/warn/Wimplicit-fallthrough-1.C
> index e69de29..053ed68 100644
> --- gcc/testsuite/g++.dg/warn/Wimplicit-fallthrough-1.C
> +++ gcc/testsuite/g++.dg/warn/Wimplicit-fallthrough-1.C
> @@ -0,0 +1,33 @@
> +// PR c++/77803
> +// { dg-do compile { target c++11 } }
> +// { dg-options "-Wimplicit-fallthrough" }
> +
> +struct A {};
> +int a;
> +
> +void
> +fn1 ()
> +{
> +  switch (0) {
> +  case 0:
> +  {
> +    A b;
> +    [[fallthrough]];
> +  }
> +  default:
> +    a = 0;
> +  }
> +}
> +
> +void
> +fn2 ()
> +{
> +  switch (0) {
> +  case 0:
> +  {
> +    A b; // { dg-warning "statement may fall through" }
> +  }
> +  default:
> +    a = 0;
> +  }
> +}
> 
> 	Marek

	Marek