How to debug .NET Runtime tests inside Docker?

[Maximys]

Hello everybody!
Can anybody explain me how to build .NET Runtime and debug tests inside Docker? I trying next command:
docker run -v C:\runtime\:/runtime -w /runtime mcr.microsoft.com/dotnet-buildtools/prereqs:ubuntu-18.04 ./build.sh
but result is:

/runtime/eng/common/tools.sh: line 501: /runtime//.dotnet/dotnet: No such file or directory
Build failed with exit code 127. Check errors above.

[Clockwork-Muse]

You're going to have a much better time if you clone inside WSL and open the devcontainer (or clone inside a volume and then open the devcontainer). For one thing, there are performance penalties for mounting the Windows filesystem inside of Linux (as you're doing with the -v volume mount). For another, it will also enable you to get interactive access to the code.

[Maximys]

@Clockwork-Muse , thanks. Can you provide more detailed info about that?

[am11]

/runtime/eng/common/tools.sh: line 501: /runtime//.dotnet/dotnet: No such file or directory
Build failed with exit code 127. Check errors above.

This error means runtime/.dotnet/dotnet exists but it is not a linux ELF executable. Try deleting artifacts and .dotnet directories before running that docker command.

and debug tests inside Docker?

I use privileged and interactive mode when debugging in container is needed:
docker run --privileged -v$(pwd):/runtime -w /runtime --it $CID bash
and install lldb inside the container. When running the .NET executable under lldb, remember to disable ASLR (gdb does this automatically but lldb does not):

$ lldb -- /runtime/artifacts/<path/to/some_executable> <args of that executable>
(lldb) settings set target.disable-aslr false
# now you can set the breakpoints and `run` etc.

or start lldb as lldb -o "settings set target.disable-aslr false" <rest of the command> or put disable-aslr command in your ~/.lldbinit file.

For more info, see https://github.com/dotnet/runtime/tree/main/docs/workflow/debugging; some of the info is missing in our docs, so feel free to send a PR based on what you experienced setting it up. Good luck!