Re: Enable -Wreturn-type by default ?

[Sylvestre Ledru <sylvestre at debian dot org>]

Hello,

On 13/11/2013 17:42, Sylvestre Ledru wrote:
> Hello,
>
> I would like to propose the activation by default of -Wreturn-type.
>
So, here is an update on this subject. Feedbacks are more than welcome
(my first gcc patch).

=== return-type-by-default-and-missing-return.diff ===
implements
1) -Wreturn-type enabled by default

2) Introduce back the option -Wmissing-return (enabled by -Wall)
to manage cases like the one from Jonathan Wakely

int f(int c) {
    if (c)
          return 0;
    function_that_never_returns();
}

$ gcc -Wmissing-return -c foo.c
foo.c: In function ÂfÂ:
foo.c:7:1: warning: control reaches end of non-void function
[-Wmissing-return]
 }
 ^

I will split this patch before submitting it.

=== return-type-by-default-and-missing-return-test-suite.diff.gz ===
Update the testsuite (for now, 715 files modified, more to come).

As you can imagine, it was a great fun ... ;)

Basically, there were several cases:
1) Add return 0; (or return true;)
to make sure that the function returns something

2) Add -Wno-return-type to dg-options / dg-lto-options when it is too
hard to construct the type to return

3) explicit declaration of the function like:
-t()
+void t()

4) idem with main
-main() {
+int main() {


=== What next? ===

There are some other tests to fix.
There are also the fortran tests to fix. Many of them (about 95) are
failing because of -Wreturn-type
Before finishing everything and sending to gcc patches, I would like to
know if I am on the right track and/or
if I am missing things.

Thanks
Sylvestre


Index: gcc/c-family/c.opt
===================================================================
--- gcc/c-family/c.opt	(révision 205009)
+++ gcc/c-family/c.opt	(copie de travail)
@@ -665,9 +665,13 @@
 Warn about returning a pointer/reference to a local or temporary variable.
 
 Wreturn-type
-C ObjC C++ ObjC++ Var(warn_return_type) Warning LangEnabledBy(C ObjC C++ ObjC++,Wall)
+C ObjC C++ ObjC++ Var(warn_return_type) Init(1) Warning
 Warn whenever a function's return type defaults to \"int\" (C), or about inconsistent return types (C++)
 
+Wmissing-return
+C ObjC C++ ObjC++ Var(warn_missing_return) Warning LangEnabledBy(C ObjC C++ ObjC++,Wall)
+Warn whenever control may reach end of non-void function
+
 Wselector
 ObjC ObjC++ Var(warn_selector) Warning
 Warn if a selector has multiple methods
Index: gcc/fortran/options.c
===================================================================
--- gcc/fortran/options.c	(révision 205009)
+++ gcc/fortran/options.c	(copie de travail)
@@ -717,6 +717,10 @@
       warn_return_type = value;
       break;
 
+    case OPT_Wmissing_return:
+      warn_missing_return = value;
+      break;
+
     case OPT_Wsurprising:
       gfc_option.warn_surprising = value;
       break;
Index: gcc/tree-cfg.c
===================================================================
--- gcc/tree-cfg.c	(révision 205009)
+++ gcc/tree-cfg.c	(copie de travail)
@@ -8067,7 +8067,7 @@
 
   /* If we see "return;" in some basic block, then we do reach the end
      without returning a value.  */
-  else if (warn_return_type
+  else if (warn_missing_return
 	   && !TREE_NO_WARNING (cfun->decl)
 	   && EDGE_COUNT (EXIT_BLOCK_PTR->preds) > 0
 	   && !VOID_TYPE_P (TREE_TYPE (TREE_TYPE (cfun->decl))))
@@ -8082,7 +8082,7 @@
 	      location = gimple_location (last);
 	      if (location == UNKNOWN_LOCATION)
 		  location = cfun->function_end_locus;
-	      warning_at (location, OPT_Wreturn_type, "control reaches end of non-void function");
+	      warning_at (location, OPT_Wmissing_return, "control reaches end of non-void function");
 	      TREE_NO_WARNING (cfun->decl) = 1;
 	      break;
 	    }

Attachment: return-type-by-default-and-missing-return-test-suite.diff.gz
Description: application/gzip