The interface __wcrtomb_chk() shall function in the same way as the interface wcrtomb(), except that __wcrtomb_chk() shall check for buffer overflow before computing a result. If an overflow is anticipated, the function shall abort and the program calling it shall exit.
The parameter buflen specifies the size of the object
pointed to by s. If it is less than
then the function shall abort
and the program calling it shall exit.
The __wcrtomb_chk() function is not in the source standard; it is only in the binary standard.