5.7.3.1 Ansi Option

The -ansi option ensures the C program strictly conforms to the C90 standard.

When specified, this option disables certain GCC language extensions when compiling C source. Such extension 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.