C++ - passing references to std::shared_ptr or boost::shared_ptr

Question

If I have a function that needs to work with a shared_ptr, wouldn\'t it be more efficient to pass it a reference to it (so to avoid copying the shared_ptr

Answer 1

I would advise against this practice unless you and the other programmers you work with really, really know what you are all doing.

First, you have no idea how the interface to your class might evolve and you want to prevent other programmers from doing bad things. Passing a shared_ptr by reference isn't something a programmer should expect to see, because it isn't idiomatic, and that makes it easy to use it incorrectly. Program defensively: make the interface hard to use incorrectly. Passing by reference is just going to invite problems later on.

Second, don't optimize until you know this particular class is going to be a problem. Profile first, and then if your program really needs the boost given by passing by reference, then maybe. Otherwise, don't sweat the small stuff (i.e. the extra N instructions it takes to pass by value) instead worry about design, data structures, algorithms, and long-term maintainability.