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The MoarVM Debugger allows you to connect to a local MoarVM instance - if it was started with the --debug-port argument passed to MoarVM itself - and control execution of threads, introspect the stack and individual objects.

MoarVM also takes the --debug-suspend commandline argument, which causes MoarVM to immediately pause execution at the start.

Start the moar-remote script and pass the port you used for --debug-port and it should connect.

Type "help" in the debugger's CLI to see what commands are available to you.

Beta Use Instructions

  1. Install the module (you may need to disable tests): zef install --/test App::MoarVM::Debug
  2. Locate perl6-m bash script (or perl6.bat on Windows): locate perl6-m
  3. Copy it to some other name: cp perl6-m perl6-moar-remote-m
  4. Edit it to include --debug-port=9999 and --debug-suspend in moar options: […] install/bin/moar --debug-port=9999 --debug-suspend --execname=[…]
  5. Start the program you want to debug using that new script: perl6-moar-remote-m my-script.pl
  6. Start the debugger CLI app and have it connect to the same port that's in the shell script from step 4: moar-remote 9999
  7. (Optional) Write assume thread 1 to assume tracking of first thread
  8. Set a breakpoint breakpoint "my-script.pl" 1234 1 1 the string is the filename and 1234 is the line number (1 1 is the secret ingredient). Ensure the line number doesn't point to an empty line.
  9. Type resume to run your script.
  10. The breakpoint will trigger, you can type all lexicals to view all lexicals. The numbers shown next to them in bold are "handle" numbers.
  11. Find the object you want to dump and run metadata 1234 (1234 is the handle number).
    • If the features includes attributes, you can enter attributes 1234 for this object.
    • If the features includes positional, positionals 1234 will work.
    • If the features includes associative, associatives 1234 will work.
    • The metadata command is only needed if you don't know which of these commands is useful for any given type.
  12. Type help to see all of the available commands.

Known Issues

The only stepping mode currently available is Step Into.

Backtraces will show incorrect line numbers.