https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90229
--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> --- $ cat 1.ii extern int FLAGS_verbose; extern "C" void pthread_create(); void a(const char *b...) { if (FLAGS_verbose) { __builtin_va_list ap; __builtin_va_start(ap, b); } } void a() { pthread_create(); } int main() { a(""); return 0; }