[110633] in cryptography@c2.net mail archive
Re: More on in-memory zeroisation
daemon@ATHENA.MIT.EDU (Thierry Moreau)
Thu Dec 13 13:51:54 2007
Date: Tue, 11 Dec 2007 20:53:06 -0500
From: Thierry Moreau <thierry.moreau@connotech.com>
To: "Leichter, Jerry" <leichter_jerrold@emc.com>
CC: Peter Gutmann <pgut001@cs.auckland.ac.nz>, cryptography@metzdowd.com
In-Reply-To: <Pine.SOL.4.61.0712111649430.29938@mental>
Leichter, Jerry wrote:
> If the function is defined as I suggested - as a static or inline - you
> can, indeed, takes its address. (In the case of an inline, this forces
> the compiler to materialize a copy somewhere that it might not otherwise
> have produced, but not to actually *use* that copy, except when you take
> the address.) You are allowed to invoke the function using the address
> you just took. However, what in that tells you that the compiler -
> knowing exactly what code will be invoked - can't elide the call?
Case of static function definition: the standard says that standard
library headers *declare* functions, not *define* them.
Case of inline: I don't know if inline definition falls in the standard
definition of declaration.
Also, the standard refers to these identifiers as external linkage. This
language *might* not creare a mandatory provision if there was a
compelling reason to have static or inline implementation, but I doubt
the very infrequent use of (memset)(?,0,?) instead of memset(?,0,?) is a
significant optimization opportunity. The compiler writer risks a
non-compliance assessment in making such strectched reading of the
standard in the present instance, for no gain in any benchmark or
production software speed measurement.
Obviously, a pointer to an external linkage scope function must adhere
to the definition of pointer equality (==) operator.
Maybe a purposedly stretched reading of the standard might let you make
your point. I don't want to argue too theoretically. Peter and I just
want to clear memory!
Kind regards,
--
- Thierry Moreau
CONNOTECH Experts-conseils inc.
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Tel.: (514)385-5691
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