linux-kernel - Re: Q: why didn't GCC warn about this uninitialized variable?

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Date:	Thu, 03 Mar 2016 04:49:25 -0800
From:	Joe Perches <joe@...ches.com>
To:	Ingo Molnar <mingo@...nel.org>,
	Måns Rullgård <mans@...sr.com>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Colin King <colin.king@...onical.com>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	Richard Henderson <rth@...ddle.net>,
	Jakub Jelinek <jakub@...hat.com>,
	Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: Q: why didn't GCC warn about this uninitialized variable?

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.