https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89449
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Just for reference: https://gcc.gnu.org/onlinedocs/gcc-8.2.0/gcc/Common-Function-Attributes.html#Common-Function-Attributes : For functions where the arguments are not available to be checked (such as vprintf), specify the third parameter as zero. In this case the compiler only checks the format string for consistency.