Message-ID: <1457009365.4044.115.camel@perches.com>
Subject: Re: Q: why didn't GCC warn about this uninitialized variable?
From: Joe Perches <joe@perches.com>
To: Ingo Molnar <mingo@kernel.org>,
        =?ISO-8859-1?Q?M=E5ns_Rullg=E5rd?= <mans@mansr.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Colin King <colin.king@canonical.com>, Ingo Molnar <mingo@redhat.com>,
        linux-kernel@vger.kernel.org, Richard Henderson <rth@twiddle.net>,
        Jakub Jelinek <jakub@redhat.com>,
        Dan Carpenter <dan.carpenter@oracle.com>
Date: Thu, 03 Mar 2016 04:49:25 -0800
In-Reply-To: <20160303124319.GA8781@gmail.com>
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On Thu, 2016-03-03 at 13:43 +0100, Ingo Molnar wrote:
>  it would be absolutely fantastic if one of these solutions existed on GCC:> 
> 
> ?- emit a warning if a structure is passed around uninitialized. A new GCC
> ???__attribute__((struct_fully_initialized)) could be used to annotate extern
> ???function arguments which fully initialize input arguments.
> 
> ???(I'd personally migrate both tools/perf and kernel side code to use it, module
> ????by module.)
> 
> ?- or memset() to zero all on-stack structures that GCC cannot prove are
> ???initialized fully.
> 
> The first solution takes extra work on the source level, the latter takes extra?
> runtime profiling to find where the extra memset()s matter to performance. Any of?
> these would be fantastic tools for C robustness and security.

Maybe memset any alignment padding between automatic variables too.