Did you *really* zeroize that key?

[Kevin Elliott]

At 11:58 -0500  on  11/6/02, Perry E. Metzger wrote:
>Someone wrote to me:
>>  According to K&R 2nd Ed. p. 211, compilers may ignore
>>  "volatile"; volatile objects have no implementation-
>>  independent semantics.
>
>K&R is not the C standard. Quoting the C99 standard, section 6.7.3.6:
>
>      An object that has volatile-qualified type may be modified in
>      ways unknown to the implementation or have other unknown side
>      effects. Therefore any expression referring to such an object
>      shall be evaluated strictly according to the rules of the
>      abstract machine, as described in 5.1.2.3. Furthermore, at every
>      sequence point the value last stored in the object shall agree
>      with that prescribed by the abstract machine, except as modified
>      by the unknown factors mentioned previously.
>
>In other words: no, "volatile" is mandatory and in fact will be
>guaranteed to be implemented as expected. This is very important --
>virtually every operating system requires "volatile" for purposes like
>writing device drivers.

Indeed.  And the suggestion that a #pragma be added to the standard 
to help prop up compilers that don't support the standard is a 
little... circular.
-- 
_____________________________________________
volatile: because every app deserves SOME interrupt code...
_____________________________________________
Kevin Elliott <mailto:kelliott at mac.com> ICQ#23758827
_____________________________________________

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