Interpreter simulator error

 All,

I stumbled upon the following error when simulating a copy of a 3.8.1
(6502) image (full log attached) :

Bitmap(Object)>>error:
        Receiver: a Bitmap of length 5499668
        Arguments and temporary variables:
                aString:        'Improper store into indexable object'
        Receiver's instance variables:
a Bitmap of length 5499668

The simulator loads the image correctly and both validate and
validateActiveContext tests pass. But when I try to run test, it throws
this error. VM version is:

4.16.7-3775 #1 XShm Tue May  5 22:44:20 IST 2020 /usr/bin/cc
Linux s400 4.4.0-104-generic #127-Ubuntu SMP Mon Dec 11 12:16:42 UTC
2017 x86_64 x86_64 x86_64 GNU/Linux

The simulator works fine with 2.2 image but gives error on a 3.8.1 image
with VMMaker loaded in it.

Has anyone seen this error before? Any help in tracing this bug is
appreciated.

Regards .. Subbu

 On 06/05/20 1:19 am, karl ramberg wrote:
>
> Bitmap(Object)>>at:put:
> Receiver: a Bitmap of length 5499668
> Arguments and temporary variables:
> index: 4902231
> value: 0.006711409395973154
> Receiver's instance variables:
> a Bitmap of length 5499668
When I trace the stack, this occurs when a float value 1.0 is stored in
the first slot of a float array of size 6 through an plugin
(FloatArrayPlugin). The Bitmap here is memory (sized in words). When
running on native VM, this code works fine but triggers an error when
simulator tries to mimic a CArray at:put:.
----
memory 4118397 (words)
a CArray
arrayBaseAddress:       14488972 (bytes)
ptrOffset:      0
unitSize:       4

CArray>>at: offset put: val
   ptrOffset = 0 ifFalse: [self error: 'only expect base address to
receive at:put: message'].
   unitSize = 1 ifTrue: [^ interpreter byteAt: arrayBaseAddress + offset
put: val].
   unitSize = 4 ifTrue: [^ interpreter longAt: arrayBaseAddress +
(offset * 4) put: val].

InterpreterSimulatorLSB>>longAt: byteAddress put: a32BitValue
   ^memory at: (byteAddress // 4) + 1 put: a32BitValue
-----
But I don't understand why a valid store into memory with an index
within bounds raises an error:
-----
Object>>at: index put: value
   index isInteger ifTrue:
     [self class isVariable
       ifTrue: [(index >= 1 and: [index <= self size])
         ifTrue: [self errorImproperStore]
         ifFalse: [self errorSubscriptBounds: index]]
-----

I could reproduce this error on released images on Ubuntu Linux (64bit
host).
* Run Squeak3.8.1-6747full.image (this contains VMMaker code)
* Open a workspace and inspect:
     InterpreterSimulator new openOn: 'Squeak32-3.8g-6548.image')
* run 'self test' from the code pane of inspector
* after swapping bytes and relocating objects, an error dialog pops up
(see attached log)

Regards .. Subbu