DUK_INTERNAL void duk_err_handle_error(const char *filename, duk_int_t line, duk_hthread *thr, duk_errcode_t code, const char *fmt, ...) {
	va_list ap;
	char msg[DUK__ERRFMT_BUFSIZE];
	va_start(ap, fmt);
	(void) DUK_VSNPRINTF(msg, sizeof(msg), fmt, ap);
	msg[sizeof(msg) - 1] = (char) 0;
	duk_err_create_and_throw(thr, code, msg, filename, line);
	va_end(ap);  /* dead code, but ensures portability (see Linux man page notes) */
}
DUK_INTERNAL void duk_fb_sprintf(duk_fixedbuffer *fb, const char *fmt, ...) {
	duk_size_t avail;
	va_list ap;

	va_start(ap, fmt);
	avail = (fb->offset >= fb->length ? (duk_size_t) 0 : (duk_size_t) (fb->length - fb->offset));
	if (avail > 0) {
		duk_int_t res = (duk_int_t) DUK_VSNPRINTF((char *) (fb->buffer + fb->offset), avail, fmt, ap);
		if (res < 0) {
			/* error */
		} else if ((duk_size_t) res >= avail) {
			/* (maybe) truncated */
			fb->offset += avail;
			if ((duk_size_t) res > avail) {
				/* actual chars dropped (not just NUL term) */
				fb->truncated = 1;
			}
		} else {
			/* normal */
			fb->offset += res;
		}
	}
	va_end(ap);
}
DUK_LOCAL void duk__handle_error(const char *filename, duk_int_t line, duk_hthread *thr, duk_errcode_t code, const char *fmt, va_list ap) {
	char msg[DUK__ERRFMT_BUFSIZE];
	(void) DUK_VSNPRINTF(msg, sizeof(msg), fmt, ap);
	msg[sizeof(msg) - 1] = (char) 0;
	duk_err_create_and_throw(thr, code, msg, filename, line);
}