The memcmp() function shall compare the first n bytes (each
interpreted as unsigned char) of the object pointed to by s1 to
the first n bytes of the object pointed to by s2.
The sign of a non-zero return value shall be determined by the sign of the
difference between the values of the first pair of bytes (both interpreted as
type unsigned char) that differ in the objects being compared.
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html