On Tue, 10 Mar 2009, Reini Urban wrote:
> 2009/3/9 Parrot <[email protected]>:
> > Comment(by doughera):
> >
> > I don't understand this ticket at all. What is this hypothetical "--
> > 64compat" ?
> >
> > I do see this puzzling note in auto/alignptrs.pm:
> >
> > # On 8-byte ptr_alignment we cannot read 4-byte pbc's. Warn the user
> > about it.
> >
> > But surely this is just a limitation of the current pbc reader code. I
> > don't see why the appropriate fix would be to ask 32-bit systems to pay a
> > penalty here instead of changing the reader code. It is certainly
> > possible to read 4-byte integers on an 8-byte system. You may have to
> > read and copy the data, but it can be done. If there's a penalty to be
> > paid, I think it's fair to have the foreign reader pay it.
>
> Sure, we can fix the reader stepping in byte steps, and not in native
> ptrsize steps.
> But it was decides to do it that way, probably it's a bit faster. I'm
> not the one
> to change that just for 64bit cpu's.
I am suggesting you consider doing just that, for 64bit machines trying to
read foreign 32bit pbcs.
> So for those Sparc64 machines with strict 8 byte ptr_alignment which
> want to read 32bit pbc's, we might either add this --64compat mode
> optionally (emit 64bit code on 32bit machines) or teach the user to
> use pbc_dump -o repacked.pbc
>
> The native read and write is not touched this way.
I don't understand this comment at all. I am not suggesting changing the
native read or write either. I am only considering the problem of 64bit
reading a foreign 32bit file. I see two possibilities: 1) The writer
pays the penalty of making the pbc maximally portable even for this
somewhat oddball case. 2) The reader (the one who will actually *use*
this facility) pays the penalty of having somewhat slower reading. I am
suggesting it makes sense to consider number 2. Of course if you can make
the "penalty" in number 1 very minimal or even non-existent, then that's
great.
I don't know exactly where in the code this issue is coming up, so I don't
have any informed opinion about how best to change it. I have tried
reading the relevant tickets, but I can't find specific information on
*where* this problem is occuring.
--
Andy Dougherty [email protected]_______________________________________________
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