Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!umd5!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.unix.wizards
Subject: alloca
Message-ID: <11920@mimsy.UUCP>
Date: 11 Jun 88 10:01:41 GMT
References: <16018@brl-adm.ARPA> <500@philmds.UUCP>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 25

Put it this way:  If you have a stack or an emulation of a stack (as
required by recursive functions), and if `alloca' is a compiler
builtin, the concept can be implemented.  Hence alloca can be *made*
portable to any C compiler, if only by fiat (declare that henceforth
`alloca' is a keyword or is otherwise reserved).

Now the problem becomes one of convincing compiler writers that
alloca (possibly by some other name) is worth adding as a reserved
word, or (on some systems) simply writing it in assembly (either as
a routine or with `inline assembly').

Note that alloca is not a panacea, and that it can largely be simulated
with dynamically sized arrays, as in

	int n = get_n();
	{
		char like_alloca[n];
		...
	}

These are not identical concepts, but they are interrelated.  Whether
one is `more important' or `more useful' than another I will not venture
to say.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris