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From: rbutterworth@watmath.UUCP
Newsgroups: comp.lang.c
Subject: bytes don't fill words
Message-ID: <4603@watmath.UUCP>
Date: Fri, 23-Jan-87 08:20:13 EST
Article-I.D.: watmath.4603
Posted: Fri Jan 23 08:20:13 1987
Date-Received: Sat, 24-Jan-87 04:39:59 EST
Distribution: comp
Organization: U of Waterloo, Ontario
Lines: 19

If it doesn't do so already, the ANSI C standard should explicitly
state the following:

1) BITS_PER_WORD%BITS_PER_BYTE need not necessarily be 0.

2) Given TypeA and TypeB, such that sizeof(TypeA) > sizeof(TypeB)
and sizeof(TypeA) % sizeof(TypeB) is 0, then for
union {TypeA a; TypeB b[sizeof(TypeA)/sizeof(TypeB)];} u;
assigning values to all the individual members of array u.b will
in some well-defined implementation-defined manner assign values
to all the bits of u.a (but not necessarily of u itself).

3) The behaviour of functions memcmp(), memcpy(), etc. is
undefined if the two arguments are not pointing at similarly
aligned data.

I realize that the last two are obvious given the first, but it
took me a long time to realize that they were obvious and it would
be nice if the standard explictly pointed them out.