Re: [PATCH V2] ABI changes for MPX.

[Eli Zaretskii <eliz@gnu.org>]

> Date: Fri, 18 Dec 2015 21:24:52 +0400
> From: Joel Brobecker <brobecker@adacore.com>
> Cc: "Tedeschi, Walfred" <walfred.tedeschi@intel.com>,
> 	gdb-patches@sourceware.org
> 
> > Thanks, I understand now.  So why would a GDB user want to set
> > mpx-bnd-init-on-return to zero?  The result will always be a bound
> > violation, no?
> 
> If I understand correctly, which is a fairly big if, it will
> depend on how far in the function's execution you've gone through.
> If you return early enough that the bound registers are still
> uninitialized, then you want to initialize them to make sure that
> there will be no bound violation due to the premature return.
> On the other hand, there might be some situations where you know
> the bound registers have been set, and you want to preserve their
> value, rather than blindly setting it to zero. For instance, what
> if there was, in fact, a bound violation. Setting it to zero would
> change the program's behavior by canceling the reporting of that
> violation.
> 
> PS: FWIW, I dislike the term "initialize", here, because it always
>     begs the question: "initialize to what?". If this is the
>     terminology used in the reference documentation and is known
>     to the community working on those chips, then I guess we have
>     to go with the flow. But otherwise, I personally would advocate
>     for another term, such as "reset" or "set to zero".
>     Just my 2 cents.

Thanks.

Walfred, any additional comments?  If not, I will suggest rewording of
your additions to the manual, to the effect of what Joel wrote above.

Thanks.