--enable-threads=posix: This enables C++ exception handling for multithreaded code. --enable-__cxa_atexit: This option will result in C++ shared libraries and C++ programs that are interoperable with other linux distributions. --enable-clocale=gnu: There is a risk that some people will build ABI incompatible C++ libraries if they didn't install all of the glibc localedata. Using --enable-clocale=gnu ensures that the "right thing" is done in all cases. If you don't wish to use this option, then at least build the de_DE locale. When GCC finds this specific locale, then the correct locale mode (gnu) is implemented.