Fix move.h's to use a concrete RValue carrier object rather than hacking a RValue&.

For move semantics, we need to create a private "RValue" type that is used to
create move constructors and move operators.  Previously, we emulated Boost's
idea of making the RValue type a subclass of the move-only type that doesn't add
any new member fields. We then just reinterpret_cast "this" into a RValue&
depending on the fact that RValue is just a type pun for the move-only type.
This ends up being undefined behavior though (C++98 5.2.10.7).

This change makes use a concrete RValue class that contains a pointer to the
move-only type.  With -O2 on clang version 3.2 (trunk 163674), this yields
identical assembly code to the previous implementation. With -O0, we generate
2 more instructions to allocate and initialize the temporary RValue struct's
object field when calling Pass().

This should be acceptable.  The snowman says so ☃.

BUG=155436

Review URL: https://chromiumcodereview.appspot.com/11078014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@161945 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 5 insertions, 5 deletions

diff --git a/base/win/scoped_handle.h b/base/win/scoped_handle.h
index 62734b6..b5d9b5c 100644
--- a/base/win/scoped_handle.h
+++ b/base/win/scoped_handle.h
@@ -49,8 +49,8 @@ class GenericScopedHandle {
   }
 
   // Move constructor for C++03 move emulation of this type.
-  GenericScopedHandle(RValue& other) : handle_(Traits::NullHandle()) {
-    Set(other.Take());
+  GenericScopedHandle(RValue other) : handle_(Traits::NullHandle()) {
+    Set(other.object->Take());
   }
 
   ~GenericScopedHandle() {
@@ -62,9 +62,9 @@ class GenericScopedHandle {
   }
 
   // Move operator= for C++03 move emulation of this type.
-  GenericScopedHandle& operator=(RValue& other) {
-    if (this != &other) {
-      Set(other.Take());
+  GenericScopedHandle& operator=(RValue other) {
+    if (this != other.object) {
+      Set(other.object->Take());
     }
     return *this;
   }