Enable semi hosting automatically in GDB after connecting to a remote target

Question

I'm using GDB to connect to a remote GDB server (OpenOCD, ARM). The program on the target uses semi hosting to print some debug messages.

I need to run in GDB these commands:

target remote 127.0.0.1:3333
monitor arm semihosting enable

Note that I must first connect to the remote target and then enable semihosting.

This works fine when running OpenOCD and gdb-multiarch from the command line. Now I would like to use an IDE: Theia and the CPP debug extension (which is based on the VS Code plugin cdt-gdb-vscode). How can I ensure that "monitor arm semihosting enable" is ran automatically after connecting to the target?

The launch.json is as follows:

{
  "version": "0.2.0",
  "configurations": [

      {
          "gdb": "gdb-multiarch",
          "type": "gdbtarget",
          "request": "attach",
          "verbose": true,
          "openGdbConsole": true,
          "openDebug": "openOnDebugBreak",
          "name": "Remote debug",
          "target": {"port": "1234", "host": "127.0.0.1"},
          "program": "${workspaceFolder}/target/thumbv7m-none-eabi/debug/example-embedded"
      }
  ]
}

I have tried adding commands to .gdbinit. Those commands are ran when I use the command line but not when using the IDE (Probably GDB is started from a different working directory).

Answer 1

Here is an example. The postRemoteConnectCommands are what your looking for.

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Launch OpenOCD Debugger",
            "type": "cppdbg",
            "request": "launch",
            "cwd": "${workspaceRoot}",
            "program": "${command:cmake.launchTargetPath}",
            "MIMode": "gdb",
            "miDebuggerPath": "gdb-multiarch.exe",
            "miDebuggerServerAddress": "localhost:3333",
            "debugServerPath": "openocd.exe",
            "debugServerArgs": "-f board/st_nucleo_f7.cfg -c \u0022$_TARGETNAME configure -rtos FreeRTOS\u0022",
            "serverStarted": "Listening on port .* for gdb connections",
            "filterStderr": true,
            "stopAtConnect": false,
            "externalConsole": true,
            "hardwareBreakpoints": {
              "require": true,
              "limit": 6
            },
            "postRemoteConnectCommands": [
              {
                "text": "-target-download",
                "ignoreFailures": false
              },
              {
                "text": "-interpreter-exec console \u0022monitor reset halt\u0022",
                "ignoreFailures": false
              },
              {
                "text": "-interpreter-exec console \u0022monitor arm semihosting enable\u0022",
                "ignoreFailures": false
              }
            ],
            "svdPath": "${workspaceRoot}/STM32F756.svd"
          }
    ]
}