GCC : and/or keywords

It seems these keywords work in GCC, and not part of a C++ standard.

Could you tell, why it's part of GC开发者_开发技巧C and where is it documented?

Actually, they are part of standards. In C, they're macros introduced by iso646.h. In C++, they're bona fide keywords. Check sections 2.5 and 2.11 of the C++ standard.

ANSI C provides these as standard; see iso646.h

They are part of ISO C++ and do not require a specific header in C++

The GCC option to disable them, -fno-operator-names, is documented in the C++ dialect options section of the GCC user manual.