Why isn't std::string::max_size a compile-time constant?

Question

std::string provides a max_size() method to determine the maximum number of elements it can contain.

However, to work out the maximum lengt

Answer 1

The call to max_size() is delegated to the allocator used for the container.

In theory, a very smart allocator could compute its max_size in runtime, e.g. depending on RAM available.