Using a custom allocator in std::string to re-use an already allocated char buffer
c++, memory-management, stdstring
Solution
`std::string` is a typedef of `basic_string` that already explicitly uses the default allocator. There is no way for `std::string` to use a different allocator. Even if you created a new typedef of `basic_string` with the allocator you wanted, it couldn't be passed to an API expecting a `std::string`.
Unfortunately I can't see any way to meet all the needs you've specified in any of the current C++ standards, unless you're able to somehow relax one or more of your requirements.
One possible creative solution, if you're able to do so, would be to allocate your "orignal" `char*` buffer as a `std::string`, utilizing `resize`. Then you could `swap` that string into your new one to make it take ownership.
Problem
I need to use an already allocated char* buffer (with the string content) in a std::string object. After some research I found that this is almost impossible and std::string would have its own private copy of data always. The only remaining way I can think of to do this is to use a custom allocator that will return the address of the already allocated char buffer. For this to work, std::string should only use the allocator to allocate memory to hold its string data and for nothing else. Is this the case?