v: $dbg statement - native V debugger REPL

[felipensp]

This idea is to provide an core debugger for V devs when using $dbg; on their code.

vdbg> h
vdbg commands:
  anon?                 check if the current context is anon
  bt                    prints a backtrace
  c, continue           continue debugging
  generic?              check if the current context is generic
  heap                  show heap memory usage
  h, help, ?            show this help
  l, list [lines]       show some lines from current break (default: 3)
  mem, memory           show memory usage
  method?               check if the current context is a method
  m, mod                show current module name
  p, print <var>        prints an variable
  q, quit               exits debugging session in the code
  scope                 show the vars in the current scope
  u, unwatch <var>      unwatches a variable
  w, watch <var>        watches a variable

Example

fn debugger(a string, b bool) {
    $dbg;
}

struct Test{}


fn (t Test) debugger[T](z T) {
    $dbg;
    dump(z)
}

fn test(params map[string]string) {
    $dbg;    
}

fn test2() {
    a := 1
    if a != 0 {
        b := 2 
        if b > 1 {
            $dbg;
        }
    }
}

fn main() {
    a := {'a': 'b', 'c': 'd'}
    d := Test{}
    d.debugger(a)

    b := 'foo'
    c := true
    println('testing vdbg')
    $dbg;
    println('after debugger;')
    test(a)
    println('after test() call')
    test2()
    debugger(b, c)
    $dbg;
}

When using $dbg in the V code, the debugger REPL will be invoked when such statement is reached in the execution, bringing to you a debugger REPL.

list

Break on [main] main in bug.v:35
bug.v:35 vdbg> l
0032      b := 'foo'
0033      c := true
0034      println('testing vdbg')
0035>     $dbg;
0036      println('after debugger;')
0037      test(a)
0038      println('after test() call')
bug.v:35 vdbg> l 2
0033      c := true
0034      println('testing vdbg')
0035>     $dbg;
0036      println('after debugger;')
0037      test(a)
bug.v:35 vdbg> l 1
0034      println('testing vdbg')
0035>     $dbg;
0036      println('after debugger;')

Inspecting variables

Break on [main] test2 in bug.v:22
bug.v:22 vdbg> l
0019      if a != 0 {
0020          b := 2 
0021          if b > 1 {
0022>             $dbg;
0023          }
0024      }
0025  }
bug.v:22 vdbg> p a
a = 1 (int)
bug.v:22 vdbg> p b
b = 2 (int)
bug.v:22 vdbg> scope
b = 2 (int)
a = 1 (int)

[smartiniOnGitHub]

Hi guys, I think this is a great feature.
Sorry didn't found related issue (if any), just a question (sorry to post here): would it be possible to have this feature disabled by default when the code has been built with the production flag (to avoid block running applications maybe for mistake) ? Thank s a lot. Bye

[felipensp]

Hi guys, I think this is a great feature. Sorry didn't found related issue (if any), just a question (sorry to post here): would it be possible to have this feature disabled by default when the code has been built with the production flag (to avoid block running applications maybe for mistake) ? Thank s a lot. Bye

File a feature request. 👍🏻

[odiroot]

anon? check if the current context is anon

May I ask, what's this?

[felipensp]

anon? check if the current context is anon

May I ask, what's this?

Check if the current context is an anon function.

[odiroot]

anon? check if the current context is anon

May I ask, what's this?

Check if the current context is an anon function.

Thanks. That's useful!