[C++ Patch] PR 51290

[Paolo Carlini]

Hi,

another case of spurious -Wzero-as-null-pointer-constant, rather 
straightforward fix, IMHO. Well, with hindsight, I should have grepped 
more carefully for integer_zero_node, a couple of weeks ago ;)

Anyway, tested x86_64-linux. Ok?

Thanks,
Paolo.

///////////////////
/cp
2011-11-23  Paolo Carlini  <paolo.carl...@oracle.com>

        PR c++/51290
        * class.c (build_base_path): For pointers, use nullptr_node instead
        of integer_zero_node.

/testsuite
2011-11-23  Paolo Carlini  <paolo.carl...@oracle.com>

        PR c++/51290
        * g++.dg/warn/Wzero-as-null-pointer-constant-3.C: New.
Index: testsuite/g++.dg/warn/Wzero-as-null-pointer-constant-3.C
===================================================================
--- testsuite/g++.dg/warn/Wzero-as-null-pointer-constant-3.C    (revision 0)
+++ testsuite/g++.dg/warn/Wzero-as-null-pointer-constant-3.C    (revision 0)
@@ -0,0 +1,22 @@
+// PR c++/51290
+// { dg-options "-Wzero-as-null-pointer-constant" }
+
+class A { int a; };
+
+class B { int b; };
+
+class C : public A, public B
+{
+    private:
+        static void foo (A *x)
+        {
+            C *y = static_cast<C *>(x);
+            (void) y;
+        }
+
+        static void bar (B *x)
+        {
+            C *y = static_cast<C *>(x);
+            (void) y;
+        }
+};
Index: cp/class.c
===================================================================
--- cp/class.c  (revision 181678)
+++ cp/class.c  (working copy)
@@ -338,7 +338,8 @@ build_base_path (enum tree_code code,
   /* Now that we've saved expr, build the real null test.  */
   if (null_test)
     {
-      tree zero = cp_convert (TREE_TYPE (expr), integer_zero_node);
+      tree zero = cp_convert (TREE_TYPE (expr),
+                             want_pointer ? nullptr_node : integer_zero_node);
       null_test = fold_build2_loc (input_location, NE_EXPR, boolean_type_node,
                               expr, zero);
     }