Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!pacbell!att!dptg!ulysses!andante!alice!ark
From: ark@alice.UUCP (Andrew Koenig)
Newsgroups: comp.lang.c
Subject: Re: `safe' putc (was avoiding stdio)
Message-ID: <10455@alice.UUCP>
Date: 7 Feb 90 04:29:02 GMT
References: <10883@attctc.Dallas.TX.US> <21689@mimsy.umd.edu> <7172@arcturus>
Distribution: usa
Organization: AT&T Bell Laboratories, Liberty Corner NJ
Lines: 29

In article <7172@arcturus>, evil@arcturus.UUCP (Wade Guthrie) writes:
> 
> chris@mimsy.umd.edu (Chris Torek) writes:
> > putc *is* *documented* as not being careful about its second parameter.
> 
> ark@alice.UUCP (Andrew Koenig) writes:
> >Has anyone out there actually written a program that depends
> >for its correct operation on side effects of the second
> >argument of putc?  
> 
> Sorry, but what are the side effects of the second argument of putc?

Putc takes two arguments: a charcter to write and a FILE* that
represents where to write it.

The following has an undefined effect:

	putc(c,*fp++);

This one, though, is well-defined:

	putc(*cp++,f);

So my question is: are there any people out there who have ever
written programs in which they wanted to take advantage of the
second argument of putc needing to be evaluated exactly once?
-- 
				--Andrew Koenig
				  ark@europa.att.com