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NNTP-Posting-Date: Wed, 27 Jun 2012 01:25:10 -0500
From: Gareth Owen <gwowen@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: Variable-length arrays: should they be used at all?
References: <jscgum$lk6$1@speranza.aioe.org> <jsd15l$28f$1@speranza.aioe.org> <jsd4ka$akr$1@speranza.aioe.org> <lnvcid4yys.fsf@nuthaus.mib.org>
Date: Wed, 27 Jun 2012 07:25:10 +0100
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Xref: csiph.com comp.lang.c:22848

Keith Thompson <kst-u@mib.org> writes:

> But the same applies to old-style constant-size arrays.  If you declare
>
>     double mat[100][100];
>
> either at block scope 

I think at block scope most people would consider that a pretty bad
idea, for exactly the same reason.  But at least you have the potential
to do static analysis to check the necessary stack size.

> or at file scope, 

At file scope, one would certainly hope that this would cause the
program would crash *at startup*.  (I appreciate this isn't guaranteed),
and, again, static analysis would tell you the minimum RAM required.  In
the embedded case, any decent compiler will tell you whether your static
data is going to eat all your RAM.

Both of which are arguably better than UB based on input size.