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From: scs@adam.mit.edu (Steve Summit)
Newsgroups: comp.lang.c
Subject: Re: scope of malloc
Summary: don't use alloca
Message-ID: <1990Nov7.234315.15508@athena.mit.edu>
Date: 7 Nov 90 23:43:15 GMT
References: <1791@sirius.ucs.adelaide.edu.au> <1990Nov07.134942.7355@virtech.uucp>
Sender: daemon@athena.mit.edu (Mr Background)
Reply-To: scs@adam.mit.edu (Steve Summit)
Organization: Thermal Technologies, Inc.
Lines: 20

In article <1990Nov07.134942.7355@virtech.uucp> cpcahil@virtech.UUCP (Conor P. Cahill) writes:
>If you just want the pointer to be around during the function, you can
>use alloca() which allocates the data on your stack.

Correction: "If you just want the pointer to be around during the
function and you want the program to be unportable...", as Doug
has just reminded us.

>This function is 
>usually hidden in the libPWB.a library.

...except under BSD, where it's right there in libc.a, and under
many other systems, where it doesn't exist at all.

The FAQ contains a bit more information on alloca.  The summary,
which bears repeating, stands: "alloca cannot be used in programs
which must be widely portable, no matter how useful it might be."

                                            Steve Summit
                                            scs@adam.mit.edu