FYI, the grandparent's meaning for 'optimal' was ambiguous, it didn't necessarily refer to efficiency. Could also be referring to bugs in the system strtod(). OTOH I agree that efficiency is the more likely interpretation, just about.
To everyone recommending CMake: have you actually viewed a reasonably-sized CMakeLists file? It's disgusting, at least as bad as configure.ac. CMake's only selling point is that it supports Windows better. (I can't comment on if it supports it particularly well.) And from the GNU folks POV, why should they support a non-free OS that more than doubles the maintenance load?