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From: sandmann AT clio DOT rice DOT edu (Charles Sandmann)
Message-Id: <10205170333.AA15841@clio.rice.edu>
Subject: Re: Malloc/free DJGPP code
To: djgpp-workers AT delorie DOT com
Date: Thu, 16 May 2002 22:33:38 -0500 (CDT)
In-Reply-To: <3CE41EB8.619484D9@yahoo.com> from "CBFalconer" at May 16, 2002 05:03:52 PM
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> It should be totally unnecessary, because the malloc code is the
> only access to sbrk provided in the whole system (barring emacs). 

sbrk() is a fairly standard unix API used to control memory.
Many programs use it when they want control over memory with lower
overhead than malloc().

Almost no unix applications call it with a negative argument, since
any library routine which did a malloc (or sbrk) could still be
expecting memory beyond what you just contracted with a negative
argument.

However, if you use the unixy sbrk() flag, I believe you should get
unix API compatible behavior, even with negative increments.

> However I see no sbrk documentation as to what is valid/invalid etc. 

Documentation can frequently be improved as far as small details.
But in this case it pretty much does what you ask it to, per the info
pages.  It's a low level routine, with no safety.  And the DJGPP
documentation is more clear and precise on what it does than either
of the two commercial unix man pages I just checked ...