VSCode Debugging

This is a guide on how to perform remote debugging via JTAG in Tock using VSCode (at the moment (Feb 2018) nRF51-DK and nRF52-DK are supported).

Requirements

  1. VSCode
  2. VSCode Native Debug Extension
  3. VSCode Rust Extension

Installation

  1. Install VSCode for your platform
  2. Open VSCode
  3. Enter the extensions menu by pressing View/Extensions
  4. Install Native Debug and Rust in that view by searching for them

You are now good to run the debugger and the debugging configurations are already set for you. But, if you want change the configuration, for example to run some special GDB commands before starting, you can do that here.

Enabling breakpoints

Let's now test if this works by configuring some breakpoints:

  1. Enter Explorer mode by pressing View/Explorer

  2. Browse and open a file where you want to enable a breakpoint

  3. In my case I want to have a breakpoint in the main in main.rs

  4. Click to the left of the line number to enable a breakpoint. You should see a red dot now as the figure below:

    Enable breakpoint VSCode

Running the debugger

  1. You need to start the GDB Server before launching a debugging session in VSCode (check out the instructions for how to do that for your board).

  2. Enter Debug mode in VSCode by pressing View/Debug. You should now see a debug view somewhere on your screen as in the figure below:

    VSCode Debug mode

  3. Choose your board in the scroll bar and then click on the green arrow or Debug/Start Debugging.

  4. You should now see that program stopped at the breakpoint as the figure below:

    Running

  5. Finally, if want to use specific GDB commands you can use the debug console in VSCode which is very useful.

Issues

  1. Sometimes GDB behaves unpredictably and stops at the wrong source line. For example, sometimes we have noticed that debugger stops at /kernel/src/support/arm.rs instead of the main. If that occurs just press step over and it should hopefully jump to correct location.

  2. Rust in release mode is optimizing using things such as inlining and mangling which makes debugging harder and values may not be visible. To perform more reliable debugging mark the important functions with:

    #[no_mangle]
#[inline(never)]

  3. Enable rust-pretty printer or something similar because viewing variables is very limited in VSCode.