In addition to the other topics on this page, we'll note here some of the C99 features that appear in libstdc++.

The C99 features depend on the --enable-c99 configure flag. This flag is already on by default, but it can be disabled by the user. Also, the configuration machinery will disable it if the necessary support for C99 (e.g., header files) cannot be found.

As of GCC 3.0, C99 support includes classification functions such as isnormal, isgreater, isnan, etc. The functions used for 'long long' support such as strtoll are supported, as is the lldiv_t typedef. Also supported are the wide character functions using 'long long', like wcstoll.