Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!yale!cmcl2!adm!smoke!gwyn
From: gwyn@smoke.BRL.MIL (Doug Gwyn)
Newsgroups: comp.std.c
Subject: Re: What about errno==0 ?
Keywords: errno, errorcheck, standard
Message-ID: <13358@smoke.BRL.MIL>
Date: 16 Jul 90 14:26:40 GMT
References: <7798@mcshh.hanse.de>
Organization: U.S. Army Ballistic Research Laboratory, APG, MD.
Lines: 12

In article <7798@mcshh.hanse.de> bkr@mcshh.hanse.de (Bjoern Kriews) writes:
-I am want to let my code now whether a routine returning NULL on failure
-failed because of an I/O Error are for a logical mistake. For example,
-I'm setting a global variable = errno after a failed malloc(), then do
-an fclose() and return. I want to set this global to zero if the code
-failed because of any error not setting errno. 
-What does the standard say about the value 0 for errno ?
-Can I assume that there is no errno.h defining any errorcode = 0 ?

As I understand your question, the answer is that all error numbers that
may be set by standard library functions are positive integers.  Therefore
you may safely assume that a code of 0 is different from any error code.