calls.lua

local doubles do
  local function iter(tab, current)
    local index = (current+1)*2
    local first, second = tab[index-1], tab[index]
    if first and second then
      return current+1, first, second
    else
      return
    end
  end

  function doubles(tab)
    return iter, tab, 0
  end
end

local function observed(fn, ...)
  local calls, size = {}, 0

  debug.sethook(function(event)
    if event == 'call' then
      local caller = debug.getinfo(3)
      local callee = debug.getinfo(2)
      calls[size+1] = caller
      calls[size+2] = callee
      size = size + 2
    end
  end, 'c')

  fn(...)

  debug.sethook()
  calls[size], calls[size-1] = nil, nil -- Remove call in above line

  return calls
end

local graph = observed(function()
  print 'Hello World'
end)

local function name(fn)
  local n
  if not fn.name or fn.name == '?' then
    n = '<function>'
  else
    n = fn.name .. ' ('..fn.namewhat..')'
  end
  return n .. ' ' .. tostring(fn.func):match("0x%x+")
end

for index, caller, callee in doubles(graph) do
  print(index, name(caller).." -> "..name(callee))
end

~about.md

A simple snippet that installs a hook recording all function calls into a table. Could be built to generate call graphs or something.