From 01ae093cbc7f347f509cfc8e53b8c2c36e0146b2 Mon Sep 17 00:00:00 2001
From: Eli Friedman <eli.friedman@gmail.com>
Date: Tue, 24 Sep 2013 23:21:41 +0000
Subject: [PATCH] Allow dynamic_cast to void* even with -fno-rtti.

PR17346.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@191340 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Sema/SemaCast.cpp    | 6 ++++--
 test/SemaCXX/no-rtti.cpp | 5 +++++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/lib/Sema/SemaCast.cpp b/lib/Sema/SemaCast.cpp
index 46b5b45306..ba00b712aa 100644
--- a/lib/Sema/SemaCast.cpp
+++ b/lib/Sema/SemaCast.cpp
@@ -669,8 +669,10 @@ void CastOperation::CheckDynamicCast() {
   Self.MarkVTableUsed(OpRange.getBegin(), 
                       cast<CXXRecordDecl>(SrcRecord->getDecl()));
 
-  // dynamic_cast is not available with fno-rtti
-  if (!Self.getLangOpts().RTTI) {
+  // dynamic_cast is not available with -fno-rtti.
+  // As an exception, dynamic_cast to void* is available because it doesn't
+  // use RTTI.
+  if (!Self.getLangOpts().RTTI && !DestPointee->isVoidType()) {
     Self.Diag(OpRange.getBegin(), diag::err_no_dynamic_cast_with_fno_rtti);
     SrcExpr = ExprError();
     return;
diff --git a/test/SemaCXX/no-rtti.cpp b/test/SemaCXX/no-rtti.cpp
index 3d6e109551..a171b3cde2 100644
--- a/test/SemaCXX/no-rtti.cpp
+++ b/test/SemaCXX/no-rtti.cpp
@@ -22,3 +22,8 @@ struct B : public A {
 bool isa_B(A *a) {
   return dynamic_cast<B *>(a) != 0; // expected-error {{cannot use dynamic_cast with -fno-rtti}}
 }
+
+void* getMostDerived(A* a) {
+  // This cast does not use RTTI.
+  return dynamic_cast<void *>(a);
+}
-- 
2.40.0