[Vm-dev] Bug in Interpreter>>primitiveNextPut:

[Eliot Miranda]

On Fri, Nov 27, 2009 at 9:03 AM, David T. Lewis <lewis at mail.msen.com> wrote:

>
> On Thu, Nov 26, 2009 at 03:10:52PM +0100, Henrik Johansen wrote:
> >
> > Interpreter >> primitiveNextPut:
> >  limit := self fetchInteger: StreamReadLimitIndex ofObject: stream.
> >       atIx := (array bitAnd: AtCacheMask) + AtPutBase.
> >       (index < limit and: [(atCache at: atIx+AtCacheOop) = array])
> >
> > so basically, it needs ReadLimit to be > 0. (Which is only true for
> (Read)WriteStreams if created with on:from:to:).
> >
> > Changing the first line to
> >  limit := self fetchInteger: StreamWriteLimitIndex ofObject: stream.
> >
> > and the primitive now works.
> > ws := WriteStream on: (String new: 500000).
> > [1 to: 500000 do: [:ix | ws nextPut: $a]] timeToRun
> >
> > before: 130
> >  after: 33
> >
> > Inserted a counter after the prim call, for the loop above it was always
> >= 500000, with fix it's >=1.
>
> Can anyone comment as to whether the above fix is correct? It looks right
> to me, but it would be good if someone familiar with #primitiveNextPut
> and the AtCache could review it.
>

The fix is correct.  c.f. the body of WriteStream>>nextPut:.

I note that this primitive has not changed since 1998, so this would
> rate as a really excellent bug catch!
>
>  http://bugs.squeak.org/view.php?id=7421
>
> Thanks,
> Dave
>
>
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