Re: Fix missing -Wimplicit-fallthrough warning

[Marek Polacek <polacek@redhat.com>]

Ping.

On Thu, Sep 29, 2016 at 06:10:27PM +0200, Marek Polacek wrote:
> Here, a missing -Wimplicit-fallthrough warning was caused by a misplaced
> FALLTHROUGH_LABEL_P check.  As it is now, for FALLTHROUGH_LABEL_P we'd
> never gotten around to
>  1933             /* So that next warn_implicit_fallthrough_r will start looking for
>  1934                a new sequence starting with this label.  */
>  1935             gsi_prev (gsi_p);
> 
> The fix is to move the check to should_warn_for_implicit_fallthrough.
> 
> Bootstrapped/regtested on x86_64-linux and ppc64-linux, ok for trunk?
> 
> 2016-09-29  Marek Polacek  <polacek@redhat.com>
> 
> 	* gimplify.c (should_warn_for_implicit_fallthrough): Check for
> 	FALLTHROUGH_LABEL_P here...
> 	(warn_implicit_fallthrough_r): ...not here.
> 
> 	* c-c++-common/Wimplicit-fallthrough-22.c: New test.
> 
> diff --git gcc/gimplify.c gcc/gimplify.c
> index 66bb8be..e077a7e 100644
> --- gcc/gimplify.c
> +++ gcc/gimplify.c
> @@ -1817,6 +1817,10 @@ should_warn_for_implicit_fallthrough (gimple_stmt_iterator *gsi_p, tree label)
>  {
>    gimple_stmt_iterator gsi = *gsi_p;
>  
> +  /* Don't warn if the label is marked with a "falls through" comment.  */
> +  if (FALLTHROUGH_LABEL_P (label))
> +    return false;
> +
>    /* Don't warn for a non-case label followed by a statement:
>         case 0:
>  	 foo ();
> @@ -1903,7 +1907,6 @@ warn_implicit_fallthrough_r (gimple_stmt_iterator *gsi_p, bool *handled_ops_p,
>  	if (gimple_code (next) == GIMPLE_LABEL
>  	    && gimple_has_location (next)
>  	    && (label = gimple_label_label (as_a <glabel *> (next)))
> -	    && !FALLTHROUGH_LABEL_P (label)
>  	    && prev != NULL)
>  	  {
>  	    struct label_entry *l;
> diff --git gcc/testsuite/c-c++-common/Wimplicit-fallthrough-22.c gcc/testsuite/c-c++-common/Wimplicit-fallthrough-22.c
> index e69de29..7a81e47 100644
> --- gcc/testsuite/c-c++-common/Wimplicit-fallthrough-22.c
> +++ gcc/testsuite/c-c++-common/Wimplicit-fallthrough-22.c
> @@ -0,0 +1,23 @@
> +/* { dg-do compile } */
> +/* { dg-options "-Wimplicit-fallthrough" } */
> +
> +void bar (int);
> +
> +void
> +foo (int i)
> +{
> +  switch (i)
> +    {
> +    case 1:
> +      bar (1);
> +      /* FALLTHROUGH */
> +    case 2:
> +      bar (2); /* { dg-warning "statement may fall through" } */
> +    case 3:
> +      bar (3); /* { dg-warning "statement may fall through" } */
> +    case 4:
> +      bar (4);
> +    default:
> +      break;
> +    }
> +}
> 
> 	Marek

	Marek