[Vm-dev] [Spur] endless recursion in forward become

[Eliot Miranda]

Hi Bert,

    it was a regression in argument validation for become introduced in
fixing argument validation for the one-way copy hash case.  The code was
erroneously checking that it had space to create copies of the input
arguments, even though it was a one-way become.  It's a copyHash become and
that confused it.  It's now fixed.  I'll generate sources and push and new
builds should appear shortly ;-)

On Thu, Jun 16, 2016 at 5:11 AM, Bert Freudenberg <bert at freudenbergs.de>
wrote:

>
> I'm reading a 20MB text file. At some point it tries to convert the 20 MB
> ByteString into an 80 MB WideString using forward become. This fails
> resulting in an endless loop. The primitive failure code for
> elementsForwardIdentityTo: (primitive 72) is  #'insufficient object memory'
> and it tries again after growing:
>
> ec == #'insufficient object memory' ifTrue:
> [Smalltalk garbageCollect < 1048576 ifTrue:
> [Smalltalk growMemoryByAtLeast: 1048576].
> ^self elementsForwardIdentityTo: otherArray].
>
> but the growMemoryByAtLeast: does not actually grow the memory:
>
> {Smalltalk garbageCollect.
> Smalltalk growMemoryByAtLeast: 1048576.
> Smalltalk garbageCollect.}
>
> ==>  #(58576608 16777216 58576608)
>
> 58 MB are not enough, but it doesn't grow any further.
>
> The question is, why does it try to allocate a new object at all? The
> WideString exists already. I thought Spur would simply install a forwarder?
>
> To reproduce, execute
>
> (ByteString new: 20000000) writeStream nextPut: (Character value: 128169)
>
> You probably want to follow that with a user interrupt (Cmd-period).
>
> This happens using the latest Spur VM from github (r201606160944)
>
> - Bert -
>
>


-- 
_,,,^..^,,,_
best, Eliot
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