Re: [patch][gcc12-changes] Add a new item about the support for automatic static variable initialization

[Kees Cook <keescook@chromium.org>]

On Tue, Sep 28, 2021 at 08:31:13PM +0000, Qing Zhao wrote:
> Hi,
> 
> This is the patch for the gcc12 changes  per your request. 
> 
> Kees provided most of the wording. 
> 
> Please take a look and let’s know whether it’s good for commit?
> 
> thanks.
> 
> Qing
> 
> ================================================
> 
> 
> From: qing zhao <qing.zhao@oracle.com>
> Date: Tue, 28 Sep 2021 12:01:42 -0700
> Subject: [PATCH] gcc-12/changes.html: Uninitialized stack variables
>  initialization update
> 
> 	* htdocs/gcc-12/changes.html (Eliminating uninitialized variables):
> 	Item about the support for automatic static variable initialization.
> ---
>  htdocs/gcc-12/changes.html | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/htdocs/gcc-12/changes.html b/htdocs/gcc-12/changes.html
> index 1f156a9..8e2979c 100644
> --- a/htdocs/gcc-12/changes.html
> +++ b/htdocs/gcc-12/changes.html
> @@ -245,6 +245,25 @@ a work-in-progress.</p>
>  <!-- .................................................................. -->
>  <h2>Other significant improvements</h2>
>  
> +<h3 id="uninitialized">Eliminating uninitialized variables</h3>
> +
> +<ul>
> +  <li>GCC can now initialize all stack variables implicitly, including
> +      padding. This is intended to eliminate all classes of uninitialized
> +      stack variable flaws. Lack of explicit initialization will still
> +      warn when <code>-Wuninitialized</code> is active. For best
> +      debugging, use of the new command-line option
> +      <code>-ftrivial-auto-var-init=pattern</code> can be used to fill
> +      variables with a repeated 0xFE pattern, which tends to illuminate
> +      many bugs (e.g. pointers receive invalid addresses, sizes and indices
> +      are very large). For best production results, the new command-line
> +      option <code>-ftrivial-auto-var-init=zero</code> can be used to
> +      fill variables with 0x00, which tends to provide a safer state for
> +      bugs (e.g. pointers are NULL, strings are NULL filled, and sizes

Minor nit: I've always been corrected that "NULL" refers to a pointer, and
"NUL" refers to the "null character", so the latter use of NULL should be
"NUL": ... pointers are NULL, strings are NUL filled, and size ...

I mix this up all the time, so apologies if that got introduced by me!
:)

-Kees

> +      and indices are 0).
> +  </li>
> +</ul>
> +
>  <h3 id="debug">Debugging formats</h3>
>  
>  <ul>
> -- 
> 1.9.1
> 
> 

-- 
Kees Cook