Should I preallocate std::stringstream?

Question

I use std::stringstream extensively to construct strings and error messages in my application. The stringstreams are usually very short life automa

Answer 1

Although "mucking around with the stringstream's rdbuf...is probably Very Easy To Get Wrong", I went ahead and hacked together a proof-of-concept anyway for fun, as it has always bugged me that there is no easy way to reserve storage for stringstream. Again, as @luke said, you are probably better off optimizing what your profiler tells you needs optimizing, so this is just to address "What if I want to do it anyway?".

Instead of mucking around with stringstream's rdbuf, I made my own, which does pretty much the same thing. It implements only the minimum, and uses a string as a buffer. Don't ask me why I called it a VECTOR_output_stream. This is just a quickly-hacked-together thing.

constexpr auto preallocated_size = 256;
auto stream = vector_output_stream(preallocated_size);
stream << "My parrot ate " << 3 << " cookies.";
cout << stream.str() << endl;