My experience has been that the awesomeness of ARC's optimizations is greatly overstated. The compiler inserts retain/release pairs around every operation that

My experience has been that the awesomeness of ARC's optimizations is greatly overstated. The compiler inserts retain/release pairs around every operation that could potentially need them, and then the optimizer eliminates the redundant ones. Pretty much the only interesting nonlocal optimization it does it turn autoreleased return values into retained returns, which isn't an issue for shared_ptr to begin with.