questions from using lint

[Chris Torek]

In article <640 at bunkerb.UUCP> garys at bunkerb.UUCP (Gary M. Samuelson) writes:
>If I say "a = b", I have clearly used the value of the expression.

Which expression?  `b', certainly, but what about the value of `a = b'?

The problem is that there really are several `kinds' of expressions
in C.  All expressions have values; but some are more useful than
others.  The following are grouped into `error' and `non-error'
classes:

	Error:			Non-Error:

	open("foo", 1);		strcpy(hold, s);
	a + 1;			a++;

My best guess at the moment at the `true' distinction between the
`error' and `non-error' classes is that the latter `end' in side
effects.  The return value from `open' is usually as important as
its side effect; but that from strcpy() is often not.  `a + 1'
has no side effects in most cases (one where it might is if integer
overflow traps are enabled); `a++' has a clear side effect.

So perhaps lint needs, in addition to /*VARARGS*/ and /*ARGSUSED*/,
and the System V style /*PRINTFLIKE*/, another pragma: /*FORSIDEEFFECTS*/.
Routines like strcpy(), strcat(), and perhaps even close(), would be
so declared in llib-lc.  This would tell lint that the return value,
though available, was purely for convenience: that the function is
normally called simply for its side effects.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 1415)
UUCP:	seismo!umcp-cs!chris
CSNet:	chris at umcp-cs		ARPA:	chris at mimsy.umd.edu