Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!cs.utexas.edu!uunet!psitech!david
From: david@psitech.UUCP (david Fridley)
Newsgroups: comp.std.c
Subject: Re: (char *)(-1)
Summary: char *sbrk();
Keywords: pointers, casts
Message-ID: <120@psitech.UUCP>
Date: 31 Jul 89 06:38:36 GMT
References: <GEOFF.89Jun11231924@onyx.cs.warwick.ac.uk> <2619@yunexus.UUCP> <18792@mimsy.UUCP>
Organization: PsiTech Inc., Fountain Valley, CA
Lines: 35

In article <18792@mimsy.UUCP>, chris@mimsy.UUCP (Chris Torek) writes:
> >>... if NULL is returned there was an error getting the next string,
> >>if (-1) is returned there were no more symbols.
> 
> >Is it safe to return -1?
> 
To quote from the my UNIX System V (Release 3.0) Programmers Reference manual
for BRK(2) (page 141):

NAME
	brk,sbrk - change data segment allocation
SYNOPSIS
	int brk (endds)
	char *endds;

	char *sbrk (incr)
	int incr;
		:
		:

DIAGNOSTICS
    Upon successful completion, brk returns a value 0 and sbrk returns the old
    break value.  Otherwise, a value of -1 is returned and errno is set to 
    indicate the error.

Here we see that sbrk(), a standard UNIX function, which returns a character
pointer will return (-1).  This is the functioin used by malloc() to get 
free more free memory from the operation system.


-- 
david.
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