C FE: improvements to ranges of bad return values

gcc/c/ChangeLog:
	* c-parser.c (c_parser_statement_after_labels): When calling
	c_finish_return, Use the return expression's location if it has
	one, falling back to the location of the first token within it.
	* c-typeck.c (c_finish_return): When issuing warnings about
	the incorrect presence/absence of a return value, issue a note
	showing the declaration of the function.

gcc/testsuite/ChangeLog:
	* gcc.dg/diagnostic-range-bad-return.c: New test case.

From-SVN: r231786

gcc/c/ChangeLog

 2015-12-16  David Malcolm  <dmalcolm@redhat.com>
 
+	* c-parser.c (c_parser_statement_after_labels): When calling
+	c_finish_return, Use the return expression's location if it has
+	one, falling back to the location of the first token within it.
+	* c-typeck.c (c_finish_return): When issuing warnings about
+	the incorrect presence/absence of a return value, issue a note
+	showing the declaration of the function.
+
+2015-12-16  David Malcolm  <dmalcolm@redhat.com>
+
 	* c-parser.c (struct c_parser): Expand array "tokens_buf" from 2
 	to 4.
 	(c_parser_peek_nth_token): New function.

gcc/c/c-parser.c

@@ -5179,7 +5179,8 @@ c_parser_statement_after_labels (c_parser *parser, vec<tree> *chain)
 	      location_t xloc = c_parser_peek_token (parser)->location;
 	      struct c_expr expr = c_parser_expression_conv (parser);
 	      mark_exp_read (expr.value);
-	      stmt = c_finish_return (xloc, expr.value, expr.original_type);
+	      stmt = c_finish_return (EXPR_LOC_OR_LOC (expr.value, xloc),
+				      expr.value, expr.original_type);
 	      goto expect_semicolon;
 	    }
 	  break;

gcc/c/c-typeck.c

@@ -9545,24 +9545,36 @@ c_finish_return (location_t loc, tree retval, tree origtype)
       if ((warn_return_type || flag_isoc99)
 	  && valtype != 0 && TREE_CODE (valtype) != VOID_TYPE)
 	{
+	  bool warned_here;
 	  if (flag_isoc99)
-	    pedwarn (loc, 0, "%<return%> with no value, in "
-		     "function returning non-void");
+	    warned_here = pedwarn
+	      (loc, 0,
+	       "%<return%> with no value, in function returning non-void");
 	  else
-	    warning_at (loc, OPT_Wreturn_type, "%<return%> with no value, "
-			"in function returning non-void");
+	    warned_here = warning_at
+	      (loc, OPT_Wreturn_type,
+	       "%<return%> with no value, in function returning non-void");
 	  no_warning = true;
+	  if (warned_here)
+	    inform (DECL_SOURCE_LOCATION (current_function_decl),
+		    "declared here");
 	}
     }
   else if (valtype == 0 || TREE_CODE (valtype) == VOID_TYPE)
     {
       current_function_returns_null = 1;
+      bool warned_here;
       if (TREE_CODE (TREE_TYPE (retval)) != VOID_TYPE)
-	pedwarn (xloc, 0,
-		 "%<return%> with a value, in function returning void");
+	warned_here = pedwarn
+	  (xloc, 0,
+	   "%<return%> with a value, in function returning void");
       else
-	pedwarn (xloc, OPT_Wpedantic, "ISO C forbids "
-		 "%<return%> with expression, in function returning void");
+	warned_here = pedwarn
+	  (xloc, OPT_Wpedantic, "ISO C forbids "
+	   "%<return%> with expression, in function returning void");
+      if (warned_here)
+	inform (DECL_SOURCE_LOCATION (current_function_decl),
+		"declared here");
     }
   else
     {

gcc/testsuite/ChangeLog

+2015-12-17  David Malcolm  <dmalcolm@redhat.com>
+
+	* gcc.dg/diagnostic-range-bad-return.c: New test case.
+
 2015-12-17  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/68946

gcc/testsuite/gcc.dg/diagnostic-range-bad-return.c

+/* { dg-options "-fdiagnostics-show-caret -Wreturn-local-addr" } */
+
+int *address_of_local (void)
+{
+  int some_local;
+  return &some_local; /* { dg-warning "function returns address of local variable" } */
+/* { dg-begin-multiline-output "" }
+   return &some_local;
+          ^~~~~~~~~~~
+   { dg-end-multiline-output "" } */
+}
+
+void surplus_return_when_void_1 (void)
+{
+  return 500; /* { dg-warning "'return' with a value, in function returning void" } */
+/* { dg-begin-multiline-output "" }
+   return 500;
+          ^~~
+   { dg-end-multiline-output "" } */
+/* { dg-begin-multiline-output "" }
+ void surplus_return_when_void_1 (void)
+      ^~~~~~~~~~~~~~~~~~~~~~~~~~
+   { dg-end-multiline-output "" } */
+}
+
+void surplus_return_when_void_2 (int i, int j)
+{
+  return i * j; /* { dg-warning "'return' with a value, in function returning void" } */
+/* { dg-begin-multiline-output "" }
+   return i * j;
+          ~~^~~
+   { dg-end-multiline-output "" } */
+/* { dg-begin-multiline-output "" }
+ void surplus_return_when_void_2 (int i, int j)
+      ^~~~~~~~~~~~~~~~~~~~~~~~~~
+   { dg-end-multiline-output "" } */
+}
+
+int missing_return_value (void)
+{
+  return; /* { dg-warning "'return' with no value, in function returning non-void" } */
+/* { dg-begin-multiline-output "" }
+   return;
+   ^~~~~~
+   { dg-end-multiline-output "" } */
+/* { dg-begin-multiline-output "" }
+ int missing_return_value (void)
+     ^~~~~~~~~~~~~~~~~~~~
+   { dg-end-multiline-output "" } */
+/* TODO: ideally we'd underline the return type i.e. "int", but that
+   location isn't captured.  */
+}