Storage allocators

[John Quarterman]

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Date: Tue, 6 Aug 85 01:11:53 PDT
From: seismo!sun!guy (Guy Harris)
To: cbosgd!std-c, ut-sally!std-unix
Subject: Re: Storage allocators

> Unix has long had an undocumented routine alloca(), which allocates
> storage off the stack.  This storage then goes away when the function
> returns.

*Some* UNIXes have had it.  It was a PWB/UNIX invention, and wiggled its way
into 4.xBSD; I don't remember it being in V7.

> ...since C supports variables on the stack, so I doubt that there are many
> machines which can't do alloca(), and for Unix, it comes down to
> documenting something that has been there for a long time.

If you said "I know that there are no machines which can't do 'alloca'", I'd
be more in favor of this proposal.  C supports variables on the stack, but
that merely requires that you can allocate a stack frame on procedure entry,
not that you can extend a stack frame during the execution of a procedure.
I would not be willing to say that all machines with C implementations can
do that.

>From the standpoint of UNIX, it's not clear that it's something that's been
there for a long time in *all* UNIXes.

	Guy Harris

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