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From: apratt@atari.UUCP
Newsgroups: comp.sys.atari.st
Subject: Re: how to allocate a big chunk of memory?
Message-ID: <706@atari.UUCP>
Date: Thu, 9-Apr-87 14:59:54 EST
Article-I.D.: atari.706
Posted: Thu Apr  9 14:59:54 1987
Date-Received: Sat, 11-Apr-87 14:28:19 EST
References: <4464@utah-cs.UUCP>
Organization: Atari Corp., Sunnyvale CA
Lines: 29
Keywords: malloc, Malloc
Summary: use Malloc

> [How can I get 200K dynamically, then free it?]
>
> -Sandra Loosemore
> sandra@utah-cs.uucp, sandra@cs.utah.edu

Use Malloc.  If you Malloc a big block, use it, and Mfree it, all will
be well.  The problems with Malloc will arise when you allocate many
blocks: no process should have more than 20 blocks Malloc-ed at a time.

Brk, sbrk, and malloc won't help you, because they all manage the
memory between your basepage and your stack pointer: this is all within
one big block that was Malloc'ed when your process started up, and is
unavailable to future applications anyway.

Of course, you have to Mshrink before you can Malloc.  But since
you are planning to exec a child, I assume you have already done that.

You don't always have to Mshrink before you can Malloc: The exceptions
are when there is a "hole" in memory, created (for instance) when you
start a shell, then start a TSR (like a ramdisk or print spooler), then
leave the shell.  The next process will load beyond the TSR, and the
memory the shell was in will be a hole.  Only explicit Malloc calls
will use up this hole; programs will always load into the largest free
block.

/----------------------------------------------\
| Opinions expressed above do not necessarily  |  -- Allan Pratt, Atari Corp.
| reflect those of Atari Corp. or anyone else. |     ...lll-lcc!atari!apratt
\----------------------------------------------/