Vladimir V writes: > But If the GNU C++ standard library extensions where stdio_sync_filebuf > belongs > supports non-posix targets then maybe include should be > moved inside _GLIBCXX_HAVE_UNISTD_H guard? > This should provide backward compatibility. I thought about using a #ifdef guard, but that relies on that definition being available when building applications using the header file, and I don't whether the definition is only available while building libstdc++ or is also available when building applications using libstdc++ -- -keith