6.7.3.1 -ansi

Support all (and only) ANSI-standard C/C++ programs. The -ansi option ensures the C/C++ program strictly conforms to the C90 standard.

When specified, this option disables certain GCC language extensions when compiling C/C++ source. Such extensions include C++ style comments, and keywords, such as asm and inline. The macro STRICT_ANSI is defined when this option is in use. See also -Wpedantic for information on ensuring strict ISO compliance.