hash.h uses std::binary_function on the string comparator function, which is an error when built as c++17 or newer because std::binary_function was removed in c++17 (after being deprecated in c++11).

With c++11 or newer, simply removing the use of std::binary_function is fine. Either builds with newer compilers that default to new language versions (GCC 11 or newer, Clang 16 or newer) need to explicitly use c++11 mode, or hash.h needs to be patched to remove use of binary_function.