error.c:692
void
#ifdef HAVE_STDARG_PROTOTYPES
rb_raise(VALUE exc, const char *fmt, ...)
#else
rb_raise(exc, fmt, va_alist)
    VALUE exc;
    const char *fmt;
    va_dcl
#endif
{
    va_list args;
    char buf[BUFSIZ];

    va_init_list(args,fmt);
    vsnprintf(buf, BUFSIZ, fmt, args);
    va_end(args);
    rb_exc_raise(rb_exc_new2(exc, buf));
}
