linux-kernel - Re: gcc fixed size char array initialization bug

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Pine.LNX.4.60.0708022231160.6774@poirot.grange>
Date:	Thu, 2 Aug 2007 22:36:59 +0200 (CEST)
From:	Guennadi Liakhovetski <g.liakhovetski@....de>
To:	Andi Kleen <andi@...stfloor.org>
cc:	linux-kernel@...r.kernel.org
Subject: Re: gcc fixed size char array initialization bug - known?

On Thu, 2 Aug 2007, Andi Kleen wrote:

> Guennadi Liakhovetski <g.liakhovetski@....de> writes:
> 
> > 	char c[4] = "0123";
> > and - a wonder - no warning. 
> 
> It's required by the C standard.
> 
> 6.7.8.14 of C99:
> ``
> An array of character type may be initialized by a character string literal, optionally
> enclosed in braces. Successive characters of the character string literal (including the
> terminating null character if there is room or if the array is of unknown size) initialize the
> elements of the array.
> ''
> 
> Note the "if there is room".
> 
> I believe the rationale is that it still allows to conveniently initialize 
> non zero terminated strings.

Right, I accept that it will compile, but I don't understand why "01234" 
produces a warning and "0123" doesn't? Don't think C99 says anything about 
that. And, AFAIU, using structs with fixed-size char array we more or less 
rely on the compiler warning us if anyone initializes it with too long a 
string.

Also interesting, that with

	char c[4] = "012345";

the compiler warns, but actually allocates a 6-byte long array...

Thanks
Guennadi
---
Guennadi Liakhovetski
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/