From:	Eric Rudd <rudd AT cyberoptics DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Freeing null
Date:	26 Feb 1997 16:26:07 GMT
Organization:	CyberOptics Corp
Lines:	18
Message-ID:	<5f1o6v$ptr@hagar.cyberoptics.com>
References:	<5etnpb$42p AT freenet-news DOT carleton DOT ca> <malyonE66p7u DOT Ju0 AT netcom DOT com> <3314684D DOT 51C1 AT blackmagic DOT tait DOT co DOT nz>
NNTP-Posting-Host:	rudd.cyberoptics.com
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To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Bill Currie <billc AT blackmagic DOT tait DOT co DOT nz> wrote:
>Roland Acton wrote:
>> 
>> Paul Derbyshire (ao950 AT FreeNet DOT Carleton DOT CA) wrote:
>> 
>> : What are the effects of free(ptr) if ptr happens to be null?

>Returns the allocated memory to the heap (*note malloc::.).  If the PTR
>is `NULL', it does nothing.

As a matter of fact, this behavior is required by the ANSI/ISO 
standard.  In sub-clause 7.10.3.2, it is stated that "If _ptr_ is 
a null pointer, no action occurs."  Thus, free(NULL) is not only 
accepted by gcc; it can be used in portable programs.

-Eric Rudd
rudd AT cyberoptics DOT com

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