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Date: Thu, 8 Mar 2018 00:05:27 -0500
From: Daniel Micay <>
To: Linus Torvalds <>
Cc: Kees Cook <>, Joern Engel <>, 
	"Tobin C. Harding" <>, "Tobin C. Harding" <>, 
	Kernel Hardening <>, Tycho Andersen <>, 
	Oleg Drokin <>, Andreas Dilger <>, 
	James Simmons <>, Greg Kroah-Hartman <>, 
	LKML <>, Herbert Xu <>, 
	Peter Zijlstra <>, Ingo Molnar <>, 
	"Gustavo A. R. Silva" <>
Subject: Re: VLA removal (was Re: [RFC 2/2] lustre: use VLA_SAFE)

On 7 March 2018 at 13:09, Linus Torvalds <> wrote:
> On Wed, Mar 7, 2018 at 9:37 AM, Kees Cook <> wrote:
>> Building with -Wvla, I see 209 unique locations reported in 60 directories:
> Ok, that's not so bad. Maybe Greg could even add it to one of those
> things he encourages new people to do?
> Because at least *some* of them are pretty trivial. For example,
> looking at the core code, I was surprised to see something in
> lib/btree.c

Some are probably just the issue of technically having a VLA that's
not really a VLA:

    static const int size = 5;

    void foo(void) {
      int x[size];

% gcc -c -Wvla foo.c
foo.c: In function ‘foo’:
foo.c:4:3: warning: ISO C90 forbids variable length array ‘x’ [-Wvla]
   int x[size];

I don't really understand why the C standard didn't make `static
const` declarations usable as constant expressions like C++. They made
the pointer conversions more painful too.

It would be nice to get rid of those cases to use -Werror=vla though.

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