puremourning / lldb-jai

LLDB formatters for Jai types

LLDB Formatters for Jai

This repo contains some LLDB formatters and synthetic child providers for Jai.

What that means is that you can print Jai types with useful output.

How to use

Put jaitype.py somewhere on the filesystem (e.g. /path/to/jai/jaitype.py), then add this to a file named ~/.lldbinit:

command script import /path/to/jai/jaitype.py

Note for Xcode, you might need .lldbinit-Xcode or one of many other confusing options.

Using with Vimspector

Here's an example .vimspector.json that you can copy/paste (modify the initCommands to specify the correct path):

{
  "$schema": "https://puremourning.github.io/vimspector/schema/vimspector.schema.json",
  "configurations": {
    "Launch": {
      "adapter": "CodeLLDB",
      "variables": {
        "buildme": {
          "shell": "jai main.jai"
        }
      },
      "configuration": {
        "request": "launch",
        "program": "${workspaceRoot}/simple_jai_test",
        "expressions": "native",
        "initCommands": [
          "command script import $HOME/Development/jai/lldb-jai/jaitype.py"
        ]
      }
    }
  }
}

Supported types

Summary for string values

The value of the string is printed:

(lldb) n
(lldb) frame variable s
(string) s = Hello, sailor!

You can see the underlying structure still, of course:

(lldb) frame variable s -R
(string) s = {
  count = 14
  data = 0x00000000002177a7
}

NOTE: Only the first 1024 characters are ever returned. This is to avoid lldb spending decades parsing data in python.

Printing arrays ($T[] and $T[..])

A summary is shown Array(count=N), along with the members, also appropriately summarised:

(lldb) var command
([] string) command = Array(count=3) {
  0 = A
  1 = B
  2 = /home/vagrant/Development/jai/tests/array_of
}

Works for [] string and [..]string

(lldb) var resizable
([..] string) resizable = Array(count=3,allocated=8) {
  0 = A
  1 = B
  2 = /home/vagrant/Development/jai/tests/array_of
}

You can print individual elements too, with usual validation:

(lldb) var command[3]
error: array index 3 is not valid for "([] string) command"
(lldb) var command[2]
(string) command[2] = /home/vagrant/Development/jai/tests/array_of