>>17
No, sorry, you're incorrect. Please don't make shit up.
By default, GCC provides some extensions to the C language that on rare occasions conflict with the C standard. See Extensions to the C Language Family. Use of the -std options listed above will disable these extensions where they conflict with the C standard version selected. You may also select an extended version of the C language explicitly with -std=gnu90 (for C90 with GNU extensions), -std=gnu99 (for C99 with GNU extensions) or -std=gnu1x (for C1X with GNU extensions). The default, if no C language dialect options are given, is -std=gnu90; this will change to -std=gnu99 in some future release when the C99 support is complete. Some features that are part of the C99 standard are accepted as extensions in C90 mode. http://gcc.gnu.org/onlinedocs/gcc/Standards.html