set_trace_func

trace.rb

set_trace_func -> (event, file, line, id, binding, classname) do
  if event == 'call' && meth = binding.eval('__method__')
    params = binding.method(meth).parameters.select{|e| e[0] != :block}
    values = params.map{|_, var| [var, binding.local_variable_get(var)]}
    printf "%8s %s:%-2d %15s %8s %s\n", event, file, line, id, classname, values.inspect
  else
    printf "%8s %s:%-2d %15s %8s\n", event, file, line, id, classname
  end
end


def foo(a,b = 0)
  bar(a, foo: true)
end
  
def bar(c, d = {})
  puts "!!!buz!!!\n"
end
  
foo('lol')

# output:
# c-return /path/to/trace.rb:1   set_trace_func   Kernel
#     line /path/to/trace.rb:12
#   c-call /path/to/trace.rb:12    method_added   Module
# c-return /path/to/trace.rb:12    method_added   Module
#     line /path/to/trace.rb:16
#   c-call /path/to/trace.rb:16    method_added   Module
# c-return /path/to/trace.rb:16    method_added   Module
#     line /path/to/trace.rb:20
#     call /path/to/trace.rb:12             foo   Object [[:a, "lol"], [:b, 0]]
#     line /path/to/trace.rb:13             foo   Object
#     call /path/to/trace.rb:16             bar   Object [[:c, "lol"], [:d, {:foo=>true}]]
#     line /path/to/trace.rb:17             bar   Object
#   c-call /path/to/trace.rb:17            puts   Kernel
#   c-call /path/to/trace.rb:17            puts       IO
#   c-call /path/to/trace.rb:17           write       IO
# !!!buz!!!
# c-return /path/to/trace.rb:17           write       IO
# c-return /path/to/trace.rb:17            puts       IO
# c-return /path/to/trace.rb:17            puts   Kernel
#   return /path/to/trace.rb:18             bar   Object
#   return /path/to/trace.rb:14             foo   Object