It’s fine with or without the std::move. The name of a local variable* is treated as an rvalue in the return statement, causing the move constructor to be invoked in both cases. The authors presumably used std::move for stylistic reasons, to make it clear that the lock is being moved. It does interfere with NRVO, … Read more
If the code looks like it should be optimized, but is not getting optimized I would submit bug here http://connect.microsoft.com/VisualStudio or raise a support case with Microsoft. This article, although it is for VC++2005 (I couldn’t find a current version of document) does explain some scenarios where it won’t work. http://msdn.microsoft.com/en-us/library/ms364057(v=vs.80).aspx#nrvo_cpp05_topic3 If we want to … Read more
Use exclusively the first method: Foo f() { Foo result; mangle(result); return result; } This will already allow the use of the move constructor, if one is available. In fact, a local variable can bind to an rvalue reference in a return statement precisely when copy elision is allowed. Your second version actively prohibits copy … Read more