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

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Message-ID: <20070802200856.GO21089@ftp.linux.org.uk>
Date:	Thu, 2 Aug 2007 21:08:56 +0100
From:	Al Viro <viro@....linux.org.uk>
To:	Guennadi Liakhovetski <g.liakhovetski@....de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: gcc fixed size char array initialization bug - known?

On Thu, Aug 02, 2007 at 09:55:51PM +0200, Guennadi Liakhovetski wrote:
> But do a
> 
> 	char c[4] = "0123";
> 
> and - a wonder - no warning.

And this is a correct behaviour.  You get a valid initialier for array;
see 6.7.8[14] for details.  Moreover, that kind of code is often
quite deliberate.

>No warning with gcc 3.3.2, 3.3.5, 3.4.5, 
> 4.1.2. I was told 4.2.x does produce a warning. Now do a
> 
> 	struct {
> 		char c[4];
> 		int i;
> 	} t;
> 	t.i = 0x12345678;
> 	strcpy(t.c, c);
> 
> and t.i is silently corrupted. Just wanted to ask if this is known, 
> really...

strcpy() from array that doesn't contain 0 is an undefined behaviour,
nothing new about that...
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