How to get a stack trace

If jank is crashing, or your AOT compiled program is, you may be asked to provide a stack trace. In case you’re not familiar with how to do this, here’s a quick rundown for both Linux (gdb) and macOS (lldb).

Note

Getting a stack trace requires invoking a debugger with your jank command. If you’re using Leiningen to invoke jank, you can get the underlying command by passing -v to Leiningen. For example, lein run -v.

Let’s say we’re trying to run jank run foo.jank.

Linux

Make sure you have gdb installed. This is likely already installed, but if it’s not, it is definitely in your package manager’s repos and it’s likely just called gdb. Once you have gdb, you can use the following.

$ gdb --args jank run foo.jank
> run
# Do whatever is needed to cause the crash.
> backtrace
# Copy this to share with others.
> quit

Note

If you want to break when an exception is thrown, use the catch throw command in gdb before you run.

macOS

On macOS, you should have lldb installed as part of your developer tools. However, you can get newer versions from Homebrew as part of the llvm package.

$ lldb -- jank run foo.jank
> run
# Do whatever is needed to cause the crash.
> backtrace
# Copy this to share with others.
> quit

Note

If you want to break when an exception is thrown, use the breakpoint set -E c++ command in lldb before you run.