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 <btc@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.