For instance, Standard C says that nearly all extensions to C are prohibited. How
silly! GCC implements many extensions, some of which were later adopted as part of
the standard. If you want these constructs to give an error message as
“required” by the standard, you must specify ‘--pedantic’, which was
implemented only so that we can say “GCC is a 100% implementation of the
standard”, not because there is any reason to actually use it.