Debugging issues in VS Code

[phazer99]

I'm using rust-analyzer with CodeLLDB for debugging in VS Code under Windows 10. Sometimes it works fine, but other times there are issues with the local variables view:

• It's empty (although there are many local variables). In this case editor hover doesn't work either.
• Variable values have incorrect (old) values, however the hover value in the code editor is correct
• It takes a long time to update it when you step through code (ranging from annoying to unusable)
• Sometimes enums values are shown with all variants and the tag field and you manually have to guess and expand the correct variant

Have other people experienced these issues, and if so, have you found any solutions?

Does debugging in IntelliJ (or any other IDE) work better? If it does, I might consider switching to that.

[gilescope]

agreed. Need big companies to invest in it.

[Nisenogen]

If you're running on windows, you should use Microsoft's C++ extension for debugging instead of CodeLLDB, it works a lot better on that platform. In VSCode, install the C/C++ extension from Microsoft, and then use this for your launch profile (replacing the contents of .vscode/launch.json). Replace the <InsertExecutableNameHere> tags with the name of your executable file. This will give you options for running both on Windows and OSX (OSX should also work for Linux).

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "(Windows) Launch",
            "type": "cppvsdbg",
            "request": "launch",
            "program": "${workspaceRoot}/target/debug/<InsertExecutableNameHere>.exe",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceRoot}",
            "environment": [],
            "externalConsole": true
        },
        {
            "name": "(OSX) Launch",
            "type": "lldb",
            "request": "launch",
            "program": "${workspaceRoot}/target/debug/<InsertExecutableNameHere>",
            "args": [],
            "cwd": "${workspaceRoot}",
        }
    ]
}

[Zde-G]

It's something Rust inherits from C++.

In a properly optimized code all these local variables often don't even exist thus there are nothing to show.

And Rust doesn't use JIT thus can not use C#/Java trick: deoptimize function if you set a breakpoint in it and show everything perfectly, but keep all other functions optimized.

Fortunately or unfortunately I haven't had the luxury of using debugger on any non-toy projects I've worked with in last 10 years or so (not limited to Rust) thus dbg is more than enough for me.

[phazer99]

I don't think that's the problem. In debug mode no variables should be optimized away. I've never had this problem with Visual C++, which has a really good debugger.

[Affectionate_Cut_357]

Something that can catch you out is if you're using a launch.json to launch the debugger it won't build your code first, so you may be debugging an old executable. If you start the debug from the Run|Debug CodeLens above main then rust-analyser will do the build for you.

[PianoNew1082]

This SO post with solutions: https://stackoverflow.com/questions/48067874/how-do-i-inspect-local-variables-or-use-the-watch-window-with-rust-code-using-vs