[squeak-dev] SIGTRAP when Proceeding from BlockCannotReturn

Marcel Taeumel marcel.taeumel at hpi.de
Thu May 5 10:48:05 UTC 2022

... Still, a VM crash is not acceptable. Is this an issue with the VM or some misused primitive?

Am 05.05.2022 12:46:50 schrieb Marcel Taeumel <marcel.taeumel at hpi.de>:
Hi Christoph --

If would be nice if we could integrate some of the proposed fixes from you and Jaromir into Trunk/6.0.

Am 04.05.2022 19:59:59 schrieb Thiede, Christoph <christoph.thiede at student.hpi.uni-potsdam.de>:

Hi Lauren,

I think this issue has already been discussed in Kernel-ct.1405 et al. (Squeak Inbox Talk might be a nice way to find all related discussions to "BlockCannotReturn"). What do you think about the solutions proposed there? :-)

Von: Squeak-dev <squeak-dev-bounces at lists.squeakfoundation.org> im Auftrag von Lauren Pullen <drurowin at gmail.com>
Gesendet: Donnerstag, 28. April 2022 07:25:44
An: squeak-dev at lists.squeakfoundation.org
Betreff: [squeak-dev] SIGTRAP when Proceeding from BlockCannotReturn
I found a VM crash while doing my UI testing.

platform sources revision VM: 202204190959
runner at Mac-1650369142700.local:work/opensmalltalk-vm/opensmalltalk-vm
Date: Tue Apr 19 11:59:48 2022 CommitHash: 2a0e785 Plugins: 202204190959
runner at Mac-1650369142700.local:work/opensmalltalk-vm/opensmalltalk-vm

If you make the novice mistake of putting a ^ in a block and evaluating
that block after the method returns, a debugger window helpfully appears
saying BlockCannotReturn.

If you press Proceed the OS will kill Squeak.  No crash.dmp file is
created for this crash.

The debugger does not respect the value of #isResumable (which
BlockCannotReturn returns true for, by the way) and always permits the
user to resume the operation using the Proceed button.  I believe there
is a method on Exception that also disregards #isResumable  To force an
operation to never proceed you must return the Exception after signaling it.

Where is the best place to fix this?  We can make the debugger respect
#isResumable and set BlockCannotReturn to return false.  We can also
make Context>>cannotReturn:to: never return normally.  We can also catch
nil in the VM.

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