tree 88d599cbcc3c88144cab55cdb4c3cef5f39db28c
parent 1bf93d73a1076223dad79c9af9113de368089436
author Martin Kustermann <kustermann@google.com> 1641976242 +0000
committer Commit Bot <commit-bot@chromium.org> 1641976242 +0000

[vm] Make stack trace generation code more conservative

If the _FutureListener.handleValue function gets deoptimized at a point
when the `this` is no longer needed/live the deoptimization procedure
may override the `this` slot in the caller frame with "<optimized out>".

This has been triggered on the "iso-stress" builder due to using VM
testing flags that cause many deoptimizations in many places.

The stack walking code should take this possibility into consideration
and be therefore conservative.

Alternatives considered:

  * Use "copy parameters" into our own frame approach - like we do
    with methods that  have optional parameters
    => This will make all unoptimized code slower.

  * Add a reachability fence to the _FutureListener.handleValue function
    => The reachabilityFench is only available in dart:_internal for VM
    => If the function could be debugged after fence but before return
       one might be able to trigger the issue nonetheless.

Closes https://github.com/dart-lang/sdk/issues/46823

TEST=Should remove flaky crashes on "iso-stress" builder.

Change-Id: I9d953706b292e02d2ba75fd794c872865faf45d0
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/227401
Reviewed-by: Alexander Markov <alexmarkov@google.com>
Reviewed-by: Slava Egorov <vegorov@google.com>
Commit-Queue: Martin Kustermann <kustermann@google.com>