Passing std:: or boost::shared_ptr as a reference to a funct

[Fahrenheit]

I was suggested to replace in few places passing const shared_ptr by value to passing by reference (e.g. change const std::shared_ptr param to const std::shared_ptr& param) when I was checking my project with PVS-Studio (http://pvs-studio.viva64.com), the static code analysis tool.

I understand that for performance hot-spots it might be a good optimization as creating a temporary copy of shared_ptr requires updating reference counter which is a interlocked operation.

So the question is - how safe is this optimization? Are there any cases when it could not be used?

Any thoughts on this would be appreciated.

[a7031x]

Don't use the const std::shared_ptr& scenario. It's not thread safe, since the referece won't increase the innter reference counter of shared_ptr. The overhead of creating a shard_ptr from another is effective and can be ignored most of time.