std::vector and std::string reallocation strategy

Question

What is the reallocation strategy used for std::string and std::vector in GCC\'s implementations?

I\'m interested in the specific strategy employed: When I append it

Answer 1

Look at the function _M_check_len in bits/stl_vector.h. It contains:

const size_type __len = size() + std::max(size(), __n);

So the basic strategy when you append n elements is either double the size or increase by n, whichever is largest. pop_back never deallocates. libc++ (LLVM) does exactly the same.

Reading the code is the only way you'll find out the strategies for string, deallocation, etc.