[squeak-dev] Wrong method source pointer in Squeak5.2

Max Leske maxleske at gmail.com
Sat Jan 12 23:08:07 UTC 2019

Hi Nicolas, hi Dave,

I did some more digging and found that the problem is actually present 
in (probably) every 5.2 image. It can easily be found by opening a fresh 
image and evaluating "self halt". In the debugger, click on "full stack" 
and scroll down to the first context (BlockClosure>>newProcess) and 
click on the entry. This will cause a SyntaxError dialog to open.

Closing both the SyntaxError dialog and the debugger makes the problem 
go away. The reason for this appears to be that opening the debugger as 
caused the UI process to be replaced with a new instance (the old 
instance was the one opened in the debugger). You can see this easily by 
evaluating "[ self halt ] fork" and clicking on the first stack frame, 
which will not cause the SyntaxError dialog to open. Alternatively, you 
could evaluate "Project current spawnNewProcessAndTerminateOld: true".

What I've discovered so far is that the problematic contexts in the UI 
process (there are multiple) are *not* the CompiledMethod instances 
installed in the respective classes. You can verify this by comparing 
"(BlockClosure>>#newProcess) identityHash" with the hash of the method 
in the context (select the third last frame, inspect the "thisContext" 
variable and evaluate "self sender sender method identityHash in that 
inspector"). After the UI process has been replaced those identity 
hashes are equal again.
The information in the "old/bad" CompiledMethod obviously points to a 
bad offset in the changes file.

I also now understand why this only affects the one specific test case: 
the test accesses the method node for each context in the current 
process, i.e. the UI process, which includes the bad contexts (access to 
the method node causes decompilation of the method which causes source 

Please let me know when you've found a solution and also if I can be of 
more help.


> Hi,
> We have an issue in Seaside where a loaded test method holds a bad 
> source pointer. We only noticed because this method accesses the 
> debugger map.
> How to reproduce:
> clone SmalltalkCI: git clone git at github.com:hpi-swa/smalltalkCI.git
> clone Seaside: git clone git at github.com:SeasideSt/Seaside.git; git 
> checkout 9cb54a7b14cd254ef318294905c4e8dda8dd9f79
> install Seaside in Squeak5.2: <path to SmalltalkCI>/run.sh --headful 
> -s Squeak-5.2 <path to Seaside>/.smalltalk.ston
> Run the test WAPharoDebuggerTest>>testNamedTempAt and you'll see a 
> debugger pop up for an UndeclaredVariable. The source lookup is 
> performed in the changes file but in the middle of a chunk of binary 
> (font) data.
> I can can only speculate that some of that binary data introduces 
> random chunks which messes with the offsets.
> We're adding a workaround for that particular test for now.
> Let me know if I can help track down the issue.
> Cheers,
> Max
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.squeakfoundation.org/pipermail/squeak-dev/attachments/20190113/30912e9e/attachment.html>

More information about the Squeak-dev mailing list