Hello Ben,
The limit you see for instance variables is due to:
- Class format encoding (Memory manager dependent)
- Bytecode set encoding (Bytecode set dependent)
The 255 inst var limit is enforced both by:
- the V3 Memory manager
- the SqueakV3PlusClosures bytecode set.
Now we have Spur instead of V3 as a memory manager, which allows up to
65535 instance variables.
The SistaV1 bytecodeset should reach production in Pharo 6 alpha any time
soon, and combined with the Spur memory manager, it enforces a limit of
65535 instance variables instead of 255.
Class variables are indeed a dictionary so there's no hard limit.
On Mon, Sep 12, 2016 at 4:51 AM, Ben Coman <b...@openinworld.com> wrote:
> Minor curiosity... I was wondering about the limits on the number of
> instance variables and class variables (particularly the latter regarding
> large FFI enumerations), so I produced a script to experiment with.
>
> Results:
> * Class Variables seem to have no practical limit. Although running 6C
> experiment a second time locks the image for about 3 minutes, but
> eventually completes.
> * Instance Variables limit is 255 or 256. This not clear since 256 works,
> but the error message** for 257 says the limit is 255.
> ** Error: genStorePopInstVarLong: index index 256 is out of range 0
> to 255
>
> cheers -ben
>
> Here is the fun script...
> "================================================"
> "The experiment has two parameters (select by changing the #at: index):
> _RANGE - Range of variables assigned. Note variables are declared
> starting from 0001.
> _TYPE - (i)instance variable or (C)lass variable"
>
> _RANGE := {
> 1->9. "1. code validation"
> 201->256. "2. instance variables limit"
> 201->257. "3. instance variables Error: genStorePopInstVarLong: index
> index 256 is out of range 0 to 255"
> 201->299. "4. class variables keep going"
> 901->999. "5. class variables go extreme"
> 9901->9999. "6. class variables go ultra extreme"
> } at: 1.
> _TYPE := {
> 'i'. "1. instance variables"
> 'C' "2. class variables"
> } at: 1.
>
> "Choose experiment parameters above"
>
> start := _RANGE key.
> end := _RANGE value.
>
> "DECLARE VARIABLES"
> vars := ''.
> 1 to: end do: [:n| vars := vars, _TYPE, (n printPaddedWith: $0 to: 4), '
> ' ].
> vars.
> Object subclass: #Test
> instanceVariableNames: ((_TYPE = 'i') ifTrue: [vars] ifFalse: [ '' ])
> classVariableNames: ((_TYPE = 'C') ifTrue: [vars] ifFalse: [ '' ])
> poolDictionaries: ''
> package: 'aaaa'.
>
> "First run needs to execute above separately to create the class referred
> below"
>
> "ASSIGN VARIABLES"
> body := '
> '.
> start to: end do: [ :n| body := body , _TYPE, (n printPaddedWith: $0 to:
> 4), ':=' , n printString , '.
> ' ].
> body.
> #Test asClass compile: 'assign ' , body.
>
> "INSPECT VARIABLES"
> body := '
> ^{'.
> start to: end do: [ :n| body := body , _TYPE, (n printPaddedWith: $0 to:
> 4) , '. ' ].
> body.
> Test compile: 'inspect ' , body , '} inspect'.
>
> Test new assign ; inspect.
>
>
