Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!lll-winken!sun-barr!newstop!sun!imagen!atari!apratt
From: apratt@atari.UUCP (Allan Pratt)
Newsgroups: comp.sys.atari.st
Subject: Re: Malloc - what it really does (was: Re: SPUFILE 2.0, C questions)
Message-ID: <1737@atari.UUCP>
Date: 23 Oct 89 19:29:10 GMT
References: <1322@engage.enet.dec.com> <1680@laura.UUCP>
Organization: Atari Corp., Sunnyvale CA
Lines: 24

klute%trillian.irb@unido.uucp (Rainer Klute) writes:

>wallace@oldtmr.dec.com (Ray Wallace) writes:
>From what I have found out Malloc (-1L) returns the *sum* of the
>sizes of *all* free memory chunks.

This is emphatically not the case, and never has been.

The original answer was right: it returns the size of the LARGEST
SINGLE CHUNK of free memory.  A common way to find out how much memory
there is in the system is to call Malloc(-1L) many times, each time
allocating a chunk of the size it returns, until it returns zero.
Then you report the answer and Mfree() all the chunks you allocated.

Of course, Malloc(-1) is evil if you're in a multi-tasking environment,
because in the time between the Malloc(-1) and actually allocating the
block of the size it reported, you could be preempted and somebody else
might allocate that block away from you!  This is only one of a whole
class of problems which a multitasking TOS would have to address: the
single-thread, global, I-own-the-machine nature of TOS applications.

============================================
Opinions expressed above do not necessarily	-- Allan Pratt, Atari Corp.
reflect those of Atari Corp. or anyone else.	  ...ames!atari!apratt