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Postings from November 2002
At 9:41 AM +0100 10/30/02, Leopold Toetsch wrote:
>Jason Gloudon wrote:
>
>>... By default both compilers align stack variables at their natural
>>alignment, so PMC pointers would normally fall on 4 byte boundaries.
>>
>>However, it is also possible that someone might save a PMC pointer to an
>>unaligned address on the stack (I can't imagine why). We could always say
>>"don't do that!" for performance reasons.
>
>So, this "someone" are we (parrot itself) + language extensions
>(PXS) which have to be compiled with the same compiler options,
>parrot is compiled with.
>Using packed structures with PMCs/Buffers inside is a strict "don't do that!".
I'm comfortable with this. If extensions use stack-allocated structs
that have misaligned PMC/Buffer pointers in them, then the extension
authors can darned well explicitly register the pointers for their
lifetime. Except in rare and bizarre cases, it would have to be done
explicitly--it's not like too many system structs are going to have
pointers to our stuff in them.
Definitely warrants a big warning in the extension docs, but that's
fine. Also warrants some seriously heavy-duty tests in the test suite
to make sure we don't trip over compiler bugs or other strange things
that would bite us because of this.
--
Dan
--------------------------------------"it's like this"-------------------
Dan Sugalski even samurai
dan@sidhe.org have teddy bears and even
teddy bears get drunk
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