Re: RFA: [PR objc/27377] Fix warnings about conditional expressions for compatible ObjC types

[David Ayers <ayers at fsfe dot org>]

Hello,

I'm wondering whether it would be OK to backport the version for the
4.3-branch while we are waiting for 4.4 release.

OK for 4.3?

Cheers,
David

gcc/
2009-03-29  David Ayers  <ayers@fsfe.org>
 
	PR objc/27377
	* c-typeck.c (build_conditional_expr): Emit ObjC warnings
	by calling objc_compare_types and surpress warnings about
	incompatible C pointers that are compatible ObjC pointers.
	
gcc/testsuite/
2009-03-29  David Ayers  <ayers@fsfe.org>

	PR objc/27377
	* objc.dg/conditional-1.m: New tests.
	
Index: gcc/c-typeck.c
===================================================================
--- gcc/c-typeck.c	(Revision 145313)
+++ gcc/c-typeck.c	(Arbeitskopie)
@@ -3393,6 +3393,7 @@
   enum tree_code code2;
   tree result_type = NULL;
   tree orig_op1 = op1, orig_op2 = op2;
+  bool objc_ok;
 
   /* Promote both alternatives.  */
 
@@ -3419,6 +3420,8 @@
       return error_mark_node;
     }
 
+  objc_ok = objc_compare_types (type1, type2, -3, NULL_TREE);
+
   /* Quickly detect the usual case where op1 and op2 have the same type
      after promotion.  */
   if (TYPE_MAIN_VARIANT (type1) == TYPE_MAIN_VARIANT (type2))
@@ -3499,7 +3502,8 @@
 	}
       else
 	{
-	  pedwarn ("pointer type mismatch in conditional expression");
+	  if (!objc_ok)
+	    pedwarn ("pointer type mismatch in conditional expression");
 	  result_type = build_pointer_type (void_type_node);
 	}
     }
Index: gcc/testsuite/objc.dg/conditional-1.m
===================================================================
--- gcc/testsuite/objc.dg/conditional-1.m	(Revision 0)
+++ gcc/testsuite/objc.dg/conditional-1.m	(Revision 0)
@@ -0,0 +1,45 @@
+/* Testing conditional warnings (without headers).  */
+/* Author: David Ayers */
+
+/* { dg-do compile } */
+
+#define nil ((id)0)
+@interface MyObject
+@end
+
+@protocol MyProtocol
+@end
+
+@interface MyProtoObject <MyProtocol>
+@end
+
+
+int
+main (int argc, char *argv[])
+{
+  id var_id = nil;
+  id <MyProtocol> var_id_p = nil;
+  MyObject *var_obj = nil;
+  MyProtoObject *var_obj_p = nil;
+
+  var_id = (var_id == var_obj) ? var_id : var_obj;
+  var_id = (var_id == var_obj) ? var_id : var_obj_p;
+
+  /* Ayers: Currently, the following test case passes for
+     technically the wrong reason (see below).
+  */
+  var_obj_p = (var_id == var_obj) ? var_obj_p : var_obj; /* { dg-warning "distinct Objective-C types" } */
+  var_obj_p = (var_id == var_obj) ? var_obj_p : var_id_p;
+
+  /* Ayers: The first of the following test cases
+     should probably warn for var_obj_p = var_obj,
+     yet that would require extensive changes to
+     build_conditional_expr to create a tree with
+     multiple types that the assignment would have
+     to evaluate both versions for correct diagnostics.
+  */
+  var_obj_p = (var_id == var_obj) ? var_id : var_obj;  
+  var_obj_p = (var_id == var_obj) ? var_id : var_obj_p;
+
+  return 0;
+}