re PR c/79152 (-Wimplicit-fallthrough false positive triggered by goto statements)

	PR c/79152
	* gimplify.c (should_warn_for_implicit_fallthrough): Handle consecutive
	non-case labels.

	* c-c++-common/Wimplicit-fallthrough-35.c: New test.

From-SVN: r244726

gcc/ChangeLog

+2017-01-20  Marek Polacek  <polacek@redhat.com>
+
+	PR c/79152
+	* gimplify.c (should_warn_for_implicit_fallthrough): Handle consecutive
+	non-case labels.
+
 2017-01-20  Alexander Monakov  <amonakov@ispras.ru>
 
 	* omp-expand.c (expand_omp_simd): Clear PROP_gimple_lomp_dev regardless

gcc/gimplify.c

@@ -1985,7 +1985,7 @@ should_warn_for_implicit_fallthrough (gimple_stmt_iterator *gsi_p, tree label)
   if (FALLTHROUGH_LABEL_P (label))
     return false;
 
-  /* Don't warn for a non-case label followed by a statement:
+  /* Don't warn for non-case labels followed by a statement:
        case 0:
 	 foo ();
        label:
@@ -1993,7 +1993,12 @@ should_warn_for_implicit_fallthrough (gimple_stmt_iterator *gsi_p, tree label)
      as these are likely intentional.  */
   if (!case_label_p (&gimplify_ctxp->case_labels, label))
     {
-      gsi_next (&gsi);
+      tree l;
+      while (!gsi_end_p (gsi)
+	     && gimple_code (gsi_stmt (gsi)) == GIMPLE_LABEL
+	     && (l = gimple_label_label (as_a <glabel *> (gsi_stmt (gsi))))
+	     && !case_label_p (&gimplify_ctxp->case_labels, l))
+	gsi_next (&gsi);
       if (gsi_end_p (gsi) || gimple_code (gsi_stmt (gsi)) != GIMPLE_LABEL)
 	return false;
     }

gcc/testsuite/ChangeLog

+2017-01-20  Marek Polacek  <polacek@redhat.com>
+
+	PR c/79152
+	* c-c++-common/Wimplicit-fallthrough-35.c: New test.
+
 2017-01-20  Thomas Preud'homme  <thomas.preudhomme@arm.com>
 
 	* lib/target-supports.exp (check_configured_with): New procedure.

gcc/testsuite/c-c++-common/Wimplicit-fallthrough-35.c

+/* PR c/79152 */
+/* { dg-do compile } */
+/* { dg-options "-Wimplicit-fallthrough" } */
+
+extern void foo (int);
+
+void
+f (int i)
+{
+  switch (i)
+    {
+    case 0:
+      foo (0);
+l1:
+      foo (1);
+    }
+
+  switch (i)
+    {
+    case 0:
+      foo (0);
+l2:;
+    }
+
+  switch (i)
+    {
+    case 0:
+      foo (0);
+l3:
+l4:
+      foo (1);
+    }
+
+  switch (i)
+    {
+    case 0:
+      foo (0);
+l5:
+l6:;
+    }
+
+  switch (i)
+    {
+    case 0:
+      foo (0); /* { dg-warning "statement may fall through" } */
+l7:
+l8:
+    case 1:
+      foo (1);
+    }
+
+  switch (i)
+    {
+    case 0:
+      foo (0); /* { dg-warning "statement may fall through" } */
+l9:
+    case 1:
+l10:
+      foo (1);
+    }
+}