[Vm-dev] Bug in #instVarAt:put: for read-only objects
Norbert Hartl
norbert at hartl.name
Sat Jan 6 12:06:12 UTC 2018
> Am 05.01.2018 um 16:53 schrieb Clément Bera <bera.clement at gmail.com>:
>
>
>
> On Fri, Jan 5, 2018 at 4:05 PM, Norbert Hartl <norbert at hartl.name <mailto:norbert at hartl.name>> wrote:
>
> You mean
>
> <primitive: 174 error: ec>
> self isReadOnlyObject
> ifTrue: [(ModificationForbidden for: self atInstVar: index with: anObject) signal]
> ifFalse: [ self primitiveFailed ]
> ?
>
> Norbert
>
> yes something like that.
>
>
> Same thing for Object>>#at:put:, floatAt:put: and so on.
I’m working on it and came by
Object>>#primitiveChangeClassTo:
and I wonder what would be the approach here. The ModificationForbidden/NoModificationError seems to be tight to an index. What would be the case for a class change? Another Exception class? How is that solved in VW?
Norbert
>
>
>> Am 05.01.2018 um 14:22 schrieb Clément Bera <bera.clement at gmail.com <mailto:bera.clement at gmail.com>>:
>>
>> Hi,
>>
>> No this is not a bug.
>>
>> This needs to be handled in the primitive failure code in the image, the method should be something like that :
>>
>> Object>>instVarAt: index put: anObject
>> <primitive: 174 error: ec>
>> self isReadOnlyObject ifTrue: [(ModificationForbidden for: self atInstVar: index with: anObject) signal]
>> self primitiveFailed
>>
>> All primitive fall-back code triggering object mutation should be rewritten this way, especially primitives such as #at:put:, #instVarAt:put:, etc.
>>
>> Cheers
>>
>> On Fri, Jan 5, 2018 at 1:42 PM, Norbert Hartl <norbert at hartl.name <mailto:norbert at hartl.name>> wrote:
>>
>> If I do
>>
>> (#foo -> #bar)
>> beReadOnlyObject;
>> value: #baz
>>
>> it throws
>>
>> ModificationForbidden: #foo->#bar is read-only, hence its field 2 cannot be modified with #baz
>>
>> which is as expected. But if I do
>>
>> (#foo -> #bar)
>> beReadOnlyObject;
>> instVarNamed: #value put: #baz
>>
>> I get
>>
>> PrimitiveFailed: primitive #instVarAt:put: in Association failed
>>
>> I think this a bug, no?
>>
>> Norbert
>>
>>
>>
>>
>> --
>> Clément Béra
>> Pharo consortium engineer
>> https://clementbera.wordpress.com/ <https://clementbera.wordpress.com/>
>> Bâtiment B 40, avenue Halley 59650 Villeneuve d'Ascq
>
>
>
>
>
> --
> Clément Béra
> Pharo consortium engineer
> https://clementbera.wordpress.com/ <https://clementbera.wordpress.com/>
> Bâtiment B 40, avenue Halley 59650 Villeneuve d'Ascq
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