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