Debugger (kdb)

kdb is Kiwi’s command-line debugger. It pauses a program before each statement so you can step through it, inspect and change variables, and set breakpoints, much like gdb or Python’s pdb.

Start it with -d (or --debug):

kiwi -d script.kiwi

The debugger pauses before the first statement, shows the surrounding source, and waits at the (kdb) prompt. The => arrow marks the line that is about to run. Standard library code is skipped: kdb only stops in your files.

Commands

Command	Short	Action
step	s	Run the current statement, stepping into function calls.
next	n	Run the current statement, stepping over function calls.
finish	f	Run until the current function returns.
run	r	Continue until the next breakpoint or the end of the program.
b <line>		Set a breakpoint at a line in the current file.
b <file>:<line>		Set a breakpoint in another file.
info b		List breakpoints with their numbers.
d <n>		Delete breakpoint number n.
p <expression>		Evaluate an expression in the current scope and print it.
locals	l	Show the variables in the current scope.
backtrace	bt	Show the call stack.
list [line]		Show the source around the current line, or around line.
help	h	Show the command list.
quit	q	Stop debugging and exit.

p runs real Kiwi code against the paused program, so it can also change state: p total = 0 resets a variable before you continue.

Example session

Given cart.kiwi:

fn total(items)
  sum = 0
  for item in items do
    sum += item
  end
  sum
end

prices = [3, 4, 5]
result = total(prices)
println "Total: ${result}"

Set a breakpoint inside the loop, run to it, and look around:

$ kiwi -d cart.kiwi
kdb - Kiwi Debugger
Debugging: cart.kiwi
Type 'h' for help, 's' to step, 'r' to run.

=> cart.kiwi:1
=>    1: fn total(items)
      2:   sum = 0
      3:   for item in items do
(kdb) b 4
Breakpoint 1 at cart.kiwi:4
(kdb) r

=> cart.kiwi:4
      2:   sum = 0
      3:   for item in items do
=>    4:     sum += item
      5:   end
      6:   sum
(kdb) bt
  #1 at total in cart.kiwi:4:5
  #0 at <main> in cart.kiwi:10:10
(kdb) l
  items = [3, 4, 5]
  sum = 0
  item = 3
(kdb) p sum + item
3
(kdb) d 1
Deleted breakpoint 1
(kdb) r
Total: 12