> Use correctly std::unique_ptr<T> has no measurable impact on performance compared with the equivalent non-smart-pointer code.
One wart of unique_ptr (and other smart pointers) is that it cannot be passed in a register when used as a function parameter, at least with the System V ABI used on Linux.
Also, the caller is responsible for destruction and there is no way to specify that a function always "consumes" a unique_ptr so the compiler cannot eliminate the destructor code: https://godbolt.org/z/sz79GoETv
Of course if the compiler can inline the call or at least controls both and can clone the function with a custom calling convention then that doesn't have to be a problem. But it still sucks that even something as seemingly simple as a tiny wrapper around a pointer does come with a cost.
One wart of unique_ptr (and other smart pointers) is that it cannot be passed in a register when used as a function parameter, at least with the System V ABI used on Linux.
Also, the caller is responsible for destruction and there is no way to specify that a function always "consumes" a unique_ptr so the compiler cannot eliminate the destructor code: https://godbolt.org/z/sz79GoETv
Of course if the compiler can inline the call or at least controls both and can clone the function with a custom calling convention then that doesn't have to be a problem. But it still sucks that even something as seemingly simple as a tiny wrapper around a pointer does come with a cost.