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From: mjs@eagle.UUCP (M.J.Shannon)
Newsgroups: net.lang.c
Subject: Re: casts to (void)
Message-ID: <1288@eagle.UUCP>
Date: Fri, 19-Jul-85 23:45:38 EDT
Article-I.D.: eagle.1288
Posted: Fri Jul 19 23:45:38 1985
Date-Received: Sat, 20-Jul-85 12:19:59 EDT
References: <11@brl-tgr.ARPA>
Organization: AT&T Bell Laboratories, Summit, NJ
Lines: 27

> 
>     Why should a cast to (void) be necessary in a statement like
> 
> 	(void) printf("foo\n");
> 
> ?  Why not say that the expression in the definition
> <statement> = <expression>";" is automatically cast to type void?
> 
> 			Gary Ansok

The cast is necessary because printf() returns a value.  Lint (very properly)
warns that the value is unused without the cast.  Would you prefer that lint
say nothing if you had a code fragment something like:

	...
	log(d);
	...

Insofar as the language is concerned, failing to do *something* with a returned
value is at least suspect.  Casting the value to void *does* use the value, but
should generate no extra code; in some implementations, it could allow better
code generation because the compiler is told explicitly to ignore the value,
perhaps leaving more (or different) registers available for subsequent code.
-- 
	Marty Shannon
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