From patchwork Fri Nov 12 16:04:17 2010
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Subject: C++ PATCH for PR/39415 (type of static_cast<cv Derived*>(Base*))
Date: Fri, 12 Nov 2010 06:04:17 -0000
From: James Dennett <jdennett@google.com>
X-Patchwork-Id: 70983
Message-Id: <AANLkTikHRemE9UNTp__fT_2REgCh31rJ9szmsyvo85KX@mail.gmail.com>
To: gcc-patches@gcc.gnu.org
Cc: Jason Merrill <jason@redhat.com>

This is a (morally 2-line) fix for PR/39415 (duplicated as PR/44916),
where static_cast<cv Derived *> could give the wrong cv-qualification,
with a short regression test.

I've tested this on Linux/x86-64 (only).

My thanks to Jason Merrill for supplying me with clues about how to
prepare and submit this .

Additional clues from others are very welcome.

-- James


Index: ChangeLog
===================================================================
--- ChangeLog	(revision 166644)
+++ ChangeLog	(working copy)
@@ -1,3 +1,8 @@
+2010-11-12  James Dennett <jdennett@google.com>
+	PR/39415
+	* cp/typeck.c (build_static_cast_1): Convert to the target type
+	when doing static_cast<cv Derived*>(Base*).
+
 2010-11-11  Nathan Froyd  <froydnj@codesourcery.com>

 	PR c/44782
Index: testsuite/g++.dg/expr/static_cast7.C
===================================================================
--- testsuite/g++.dg/expr/static_cast7.C	(revision 0)
+++ testsuite/g++.dg/expr/static_cast7.C	(revision 0)
@@ -0,0 +1,10 @@
+// Regression test for bug 39415 (and its duplicate 44916).
+struct S {};
+struct T : S {};
+int f(const T*) {}
+void f(T*);
+int main() {
+  S* s(0);
+  int a = f(static_cast<const T*>(s));
+  int b = f(static_cast<const T*>(0));
+}
Index: cp/typeck.c
===================================================================
--- cp/typeck.c	(revision 166644)
+++ cp/typeck.c	(working copy)
@@ -5884,7 +5884,8 @@ build_static_cast_1 (tree type, tree exp
       base = lookup_base (TREE_TYPE (type), TREE_TYPE (intype),
 			  c_cast_p ? ba_unique : ba_check,
 			  NULL);
-      return build_base_path (MINUS_EXPR, expr, base, /*nonnull=*/false);
+      expr = build_base_path (MINUS_EXPR, expr, base, /*nonnull=*/false);
+      return cp_fold_convert(type, expr);
     }

   if ((TYPE_PTRMEM_P (type) && TYPE_PTRMEM_P (intype))