3.3 C language standards

By default, gcc compiles programs using the GNU dialect of the C language, referred to as GNU C. This dialect incorporates the official ANSI/ISO standard for the C language with several useful GNU extensions, such as nested functions and variable-size arrays. Most ANSI/ISO programs will compile under GNU C without changes.

There are several options which control the dialect of C used by gcc. The most commonly-used options are -ansi and -pedantic. The specific dialects of the C language for each standard can also be selected with the -std option.