ar is deprecated from the LSB and is expected to disappear from a future version of the LSB.
Rationale: The LSB generally does not include software development utilities nor does it specify .o and .a file formats.
ar is as specified in POSIX 1003.1-2001 (ISO/IEC 9945-2003) but with differences as listed below.
need not be accepted.
has unspecified behavior.
has unspecified behavior; using -r is suggested.