[Vm-dev] [VM CRASH, 201710061559, Cog/Spur, Win32] Cannot step-over using object-as-method

Marcel Taeumel marcel.taeumel at hpi.de
Tue Oct 10 13:54:23 UTC 2017

Hi, there.

There seems to be a bug in the VM that occurs when stepping over a call that is actually a regular object in a method dictionary.

The VM crashes in the primitive 76.

To reproduce the bug load the attached change set and run the following code to install the "fake" method:

Blubb methodDict at: #fake put: (BlubbMethod new original: (Blubb >> #original)).

Now do this in the workspace:

self halt.
Blubb new fake.

Then "step over" a few times. The VM crashes. This is not a new bug. The VM crashes also in:

Squeak 4.6, VM 3397 (Cog V3)
Squeak 4.5, VM 2776 (Cog V3)
Squeak 4.3, VM Squeak 4.1.1 (no Cog, Stack VM)

In Squeak 4.4 (VM 2776, Cog V3), I get a "SmallInteger DNU 137504030". No VM crash. :)
In Squeak 3.8 (InterpreterVM?), I get a "Where is the jump??" error raised in MethodContext(InstructionStream) >> #skipBackBeforeJump. No VM crash. :)

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