[Vm-dev] [squeak-dev] Endless recursion: "String new: -1"

[Tobias Pape]

On 07.07.2016, at 19:48, Eliot Miranda <eliot.miranda at gmail.com> wrote:

> On Thu, Jul 7, 2016 at 10:27 AM, Tobias Pape <Das.Linux at gmx.de> wrote:
> 
> 
> On 07.07.2016, at 18:44, Eliot Miranda <eliot.miranda at gmail.com> wrote:
> 
> > On Thu, Jul 7, 2016 at 5:42 AM, Tobias Pape <Das.Linux at gmx.de> wrote:
> >
> > Hi all
> >
> > (cc vm-dev)
> > On 07.07.2016, at 14:28, David T. Lewis <lewis at mail.msen.com> wrote:
> >
> > > I think the problem is in the primitive error code checking. The primitive
> > > is failing with #'bad argument' but the fallback code attempts to handle it
> > > as #'insufficient object memory'. It then tries to free some memory, fails
> > > to correct the problem, and raises a "Space is low" notifier.
> > >
> >
> > I noted that when we moved to Spur initially and I tried to fix tests.
> > The AllocationTest failed, and I changed
> >
> >         ec == #'insufficient object memory' ifTrue:
> >
> > to
> >         (ec == #'insufficient object memory' or: [ec == #'bad argument']) ifTrue:
> >
> > in Behavior>>#basicNew:
> >
> > Maybe that was an error?
> >
> > @Eliot, why does Spur return #'bad argument' instead of #'insufficient object memory' when
> > too much memory is to be allocated?
> >
> > It doesn't.  It answers bad argument for anything other than an integer in the range 0 to 2^32-1 or 0 to 2^64-1.
> 
> But logically, it should return #'insufficient object memory' for > 2^64-1.
> 
> I disagree.  There are implementation limits.  So answering #'unsupported operation' or #'bad argument 's as logical and defensible as #'out of memory' and actually truer.  The VM does /not/ try and allocate memory beyond the address space size.  So actually the failure for > the range 0 to 2^32-1 or 0 to 2^64-1 as #'out of memory' is untrue; the reason is not because the ysste, os out of memory; the reason is that this is a bad argument, outside of the valid range of the primitive.

Why it is a problem to answer
	"I want a gazillion bytes of memory"
with
	"that's too much"
instead of
	"I don't understand you"
?
It's Smalltalk, after all, not C.

Best regards
	-Tobias
	

> 
> 
> Your change to return #'bad argument' with Spur broke AllocationTest>>#testOutOfMemorySignal which
> worked on pre-Spur Cog and interpreter.
> 
> That's a problem with the test.
>  
> 
> Best regards
>         -Tobias
> 
> PS: the test that predates spur:
> 
> testOutOfMemorySignal
>         "Ensure that OOM is signaled eventually"
>         | sz |
>         sz := 512*1024*1024. "work around the 1GB alloc bug"
>         self should:[(1 to: 2000) collect:[:i| Array new: sz]] raise: OutOfMemory.
> 
>         "Call me when this test fails, I want your machine"
>         sz := 1024*1024*1024*1024.
>         self should:[Array new: sz] raise: OutOfMemory.
> 
> The test failed, technically you have to call David lewis now ;)
> 
> Sure.  IMO this should be checking Smalltalk wordSize and choosing a value which is within the available address space.  Don't make the tail wag the dog.
>  
> 
> 
> 
> >  I think your commit of topa 10/7/2015 20:41 for Behavior>>basicNew: is wrong, and should be reverted.
> >
> >
> > Best regards
> >         -Tobias
> >
> >
> > > Dave
> > >
> > >
> > > On Thu, Jul 07, 2016 at 09:23:14AM +0200, Levente Uzonyi wrote:
> > >> Someone seems to have trimmed the versions in the changes file. In Squeak
> > >> 4.4 Behavior >> #basicNew: had the following body:
> > >>
> > >>      <primitive: 71>
> > >>      self isVariable ifFalse:
> > >>              [self error: self printString, ' cannot have variable sized
> > >>              instances'].
> > >>      (sizeRequested isInteger and: [sizeRequested >= 0]) ifTrue:
> > >>              ["arg okay; space must be low."
> > >>              OutOfMemory signal.
> > >>              ^ self basicNew: sizeRequested  "retry if user proceeds"].
> > >>      self primitiveFailed
> > >>
> > >> So, non-integer and negative arguments were primitive failures.
> > >>
> > >> Levente
> > >>
> > >>
> > >> On Wed, 6 Jul 2016, David T. Lewis wrote:
> > >>
> > >>> On Wed, Jul 06, 2016 at 06:43:25AM -0700, marcel.taeumel wrote:
> > >>>> Hi, there!
> > >>>>
> > >>>> Is it okay that there is an endless recursion when evaluating "String
> > >>>> new: -1"?
> > >>>
> > >>> No, it is not okay. It should fail with a primitive failure.
> > >>>
> > >>> Dave
> > >>>
> > >>>
> > >>>>
> > >>>> ...
> > >>>> ByteString class(Behavior)>>handleFailingFailingBasicNew:
> > >>>> ByteString class(Behavior)>>handleFailingBasicNew:
> > >>>> ByteString class(Behavior)>>basicNew:
> > >>>> ByteString class(Behavior)>>handleFailingFailingBasicNew:
> > >>>> ByteString class(Behavior)>>handleFailingBasicNew:
> > >>>> ByteString class(Behavior)>>basicNew:
> > >>>> ByteString class(Behavior)>>handleFailingFailingBasicNew:
> > >>>> ByteString class(Behavior)>>handleFailingBasicNew:
> > >>>> ByteString class(Behavior)>>basicNew:
> > >>>> ...
> > >>>>
> > >>>> I would like to have an error signaled instead. Note that the -1 is just
> > >>>> an
> > >>>> example for a bad computation. The error I get is "Space is low" then. :-)
> > >>>>
> > >>>>
> > >>>> Best,
> > >>>> Marcel
> > >>>>
> > >>>>
> > >>>>