Re: Possible patch for tree-optimization/13000

[Ian Lance Taylor <ian at airs dot com>]

Richard Henderson <rth@redhat.com> writes:

> On Thu, Jan 20, 2005 at 09:50:57PM -0500, Ian Lance Taylor wrote:
> > @@ -6764,6 +6765,16 @@ c_finish_bc_stmt (tree *label_p, bool is
> >  {
> >    tree label = *label_p;
> >  
> > +  /* In switch statements break is sometimes stylistically used after
> > +     a return statement.  This can lead to spurious warnings about
> > +     control reaching the end of a non-void function when it is
> > +     inlined.  Note that we are calling block_may_fallthru with
> > +     language specific tree nodes; this works because
> > +     block_may_fallthru returns true when given something it does not
> > +     understand.  */
> > +  if (! block_may_fallthru (cur_stmt_list))
> > +    return NULL_TREE;
> > +
> >    if (!label)
> >      *label_p = label = create_artificial_label ();
> >    else if (TREE_CODE (label) != LABEL_DECL)
> 
> Also, you've failed to issue the error needed for 
> 
> void foo()
> {
>   return;
>   break;
> }

Hmmm.

Index: c-typeck.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/c-typeck.c,v
retrieving revision 1.411
diff -p -u -r1.411 c-typeck.c
--- c-typeck.c	19 Jan 2005 09:27:17 -0000	1.411
+++ c-typeck.c	21 Jan 2005 06:41:12 -0000
@@ -43,6 +43,7 @@ Software Foundation, 59 Temple Place - S
 #include "target.h"
 #include "tree-iterator.h"
 #include "tree-gimple.h"
+#include "tree-flow.h"
 
 /* Possible cases of implicit bad conversions.  Used to select
    diagnostic messages in convert_for_assignment.  */
@@ -6762,10 +6763,23 @@ c_finish_loop (location_t start_locus, t
 tree
 c_finish_bc_stmt (tree *label_p, bool is_break)
 {
+  bool skip;
   tree label = *label_p;
 
+  /* In switch statements break is sometimes stylistically used after
+     a return statement.  This can lead to spurious warnings about
+     control reaching the end of a non-void function when it is
+     inlined.  Note that we are calling block_may_fallthru with
+     language specific tree nodes; this works because
+     block_may_fallthru returns true when given something it does not
+     understand.  */
+  skip = !block_may_fallthru (cur_stmt_list);
+
   if (!label)
-    *label_p = label = create_artificial_label ();
+    {
+      if (!skip)
+	*label_p = label = create_artificial_label ();
+    }
   else if (TREE_CODE (label) != LABEL_DECL)
     {
       if (is_break)
@@ -6775,6 +6789,9 @@ c_finish_bc_stmt (tree *label_p, bool is
       return NULL_TREE;
     }
 
+  if (skip)
+    return NULL_TREE;
+
   return add_stmt (build1 (GOTO_EXPR, void_type_node, label));
 }