As is the case on GNU.
@ -75,6 +75,7 @@ int vaswprintf(wchar_t **ret, const wchar_t *format, va_list ap) {
va_list _ap;
va_copy(_ap, ap);
errno = EOVERFLOW; // vswprintf may not set errno.
int len = vswprintf(*ret, 1 + cap, format, _ap);
va_end(_ap);