[New Release] LiveRecorder 6.9 Answers the Question of “How Did This Variable Get That Value?”

[New Release] LiveRecorder 6.9 Answers the Question of “How Did This Variable Get That Value?”

Our new release is out! Please welcome LiveRecorder 6.9 to the world, with the cheesy nickname of Colby*.

New “last” command to answer the question of “when did an expression last change value?”

It’s quite common when diagnosing an issue in your application to come across an unexpected value in a variable or data structure, and to wonder “How did that value get there?” In release 6.9 we have introduced a new last command that you can use to ask LiveRecorder and UDB to answer that question directly:

  • The last command jumps to the last time in execution history when the value of a variable or expression was modified.
  • You can keep repeating last to keep jumping back to previous times that the value changed.

Check out the docs for more information.

Reduced the time required to load LiveRecorder recordings

In release 6.8, Undo switched to using the LZ4 compression scheme for recordings, making saving and loading recordings much faster compared to the previously used compression algorithm (gzip).

Release 6.9 further reduces the time taken to load LiveRecorder recordings, particularly recordings of programs which contain many large shared libraries.

Reverse execution commands in a freshly-loaded LiveRecorder recording are up 4x faster

A common use case is to load a LiveRecorder recording at the end of the program’s execution history – often at a failed assertion or a crash – and to issue reverse-execution commands to investigate what led up to the failure.

These initial reverse execution commands will operate up to 4x faster since LiveRecorder recordings generated with release 6.9 and later contain multiple snapshots.

If you wish to review the release notes in their entirety, visit https://docs.undo.io.


Learn more about LiveRecorder



We ❤️ cheese, so we name all of our releases after some of them. If you want to find out more about Colby cheese, the inspiration for this release, here’s some worthwhile reading on Wikipedia; and here’s some reading on the city of Colby, Wisconsin after which it is named.

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