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

[Eliot Miranda]

> On Jul 7, 2016, at 1:48 PM, Tobias Pape <Das.Linux at gmx.de> wrote:
> 
> 
> 
>> 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"
> ?

That's not what the error codes mean.  #'out of memory' means "I can't find that much free memory".  #'bad argument" means a variety of things from out-of-bounds (cf at:) to wring class.

> It's Smalltalk, after all, not C.

I'm sorry.  I'm not following.

> 
> 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
> 
> 
>