(In the example, he's compiling ls with the -std=gnu99 flag, which means he's targeting GNU, not C99 or C90 or C11 or POSIX or any other standard.)
FWIW, GCC 4.7.2 parses the format string without warnings.
(In the example, he's compiling ls with the -std=gnu99 flag, which means he's targeting GNU, not C99 or C90 or C11 or POSIX or any other standard.)