mbrlen
oclen = mbrlen(op, MB_LEN_MAX, &mbs1);
nclen = mbrlen(np, MB_LEN_MAX, &mbs2);
extern size_t mbrlen(const char *_RESTRICT_KYWD, size_t,
using std::mbrlen;
char_len = mbrlen(fmt + pos, formatlen - pos, NULL);