Dbg crashes when tracing calls

[indiejames]

Attempted to follow instructions in README.md, but getting erorr with verison 1.0.1, Erlang 18, Elixir 1.2.0. Ran iex -S mix in dbg directory after mix compile then followed steps in README.m and got the following:

Erlang/OTP 18 [erts-7.2.1] [source] [64-bit] [smp:8:8] [async-threads:10] [hipe] [kernel-poll:false] [dtrace]

Interactive Elixir (1.2.0) - press Ctrl+C to exit (type h() ENTER for help)

iex(1)> Dbg.trace(self(), :call)
%{counts: %{nonode@nohost: 1}, errors: %{}}
iex(2)> Dbg.call(&Map.new/0)
%{counts: %{nonode@nohost: 1}, errors: %{}}
iex(3)> Map.new()
%{}
iex(4)> ** dbg got EXIT - terminating: {trace_handler_crashed,
{function_clause,
[{'Elixir.IEx.Config',default_option,
[width],
[{file,"lib/iex/config.ex"},{line,63}]},
{'Elixir.IEx.Config',
'-default_config/0-fun-0-',1,
[{file,"lib/iex/config.ex"},{line,60}]},
{'Elixir.Enum','-map/2-lists^map/1-0-',2,
[{file,"lib/enum.ex"},{line,1088}]},
{'Elixir.Enum','-map/2-lists^map/1-0-',2,
[{file,"lib/enum.ex"},{line,1088}]},
{'Elixir.IEx.Config',configuration,0,
[{file,"lib/iex/config.ex"},{line,56}]},
{'Elixir.Dbg.Handler',handle_event,2,
[{file,"lib/dbg/handler.ex"},{line,9}]},
{dbg,handle_traces,4,
[{file,"dbg.erl"},{line,819}]},
{dbg,tracer_loop,2,
[{file,"dbg.erl"},{line,783}]}]}}

=ERROR REPORT==== 9-Jan-2016::23:05:46 ===
** Generic server 'Elixir.Dbg.Watcher' terminating
** Last message in was {'DOWN',#Ref<0.0.4.689>,process,<0.121.0>,
{trace_handler_crashed,
{function_clause,
[{'Elixir.IEx.Config',default_option,
[width],
[{file,"lib/iex/config.ex"},{line,63}]},
{'Elixir.IEx.Config','-default_config/0-fun-0-',1,
[{file,"lib/iex/config.ex"},{line,60}]},
{'Elixir.Enum','-map/2-lists^map/1-0-',2,
[{file,"lib/enum.ex"},{line,1088}]},
{'Elixir.Enum','-map/2-lists^map/1-0-',2,
[{file,"lib/enum.ex"},{line,1088}]},
{'Elixir.IEx.Config',configuration,0,
[{file,"lib/iex/config.ex"},{line,56}]},
{'Elixir.Dbg.Handler',handle_event,2,
[{file,"lib/dbg/handler.ex"},{line,9}]},
{dbg,handle_traces,4,[{file,"dbg.erl"},{line,819}]},
{dbg,tracer_loop,2,
[{file,"dbg.erl"},{line,783}]}]}}}
** When Server state == #{'struct' => 'Elixir.Dbg.Watcher',
dbg_ref => #Ref<0.0.4.688>,
tracer => nil,
tracer_ref => nil}
** Reason for termination ==
** {trace_handler_crashed,
{function_clause,
[{'Elixir.IEx.Config',default_option,
[width],
[{file,"lib/iex/config.ex"},{line,63}]},
{'Elixir.IEx.Config','-default_config/0-fun-0-',1,
[{file,"lib/iex/config.ex"},{line,60}]},
{'Elixir.Enum','-map/2-lists^map/1-0-',2,
[{file,"lib/enum.ex"},{line,1088}]},
{'Elixir.Enum','-map/2-lists^map/1-0-',2,
[{file,"lib/enum.ex"},{line,1088}]},
{'Elixir.IEx.Config',configuration,0,
[{file,"lib/iex/config.ex"},{line,56}]},
{'Elixir.Dbg.Handler',handle_event,2,
[{file,"lib/dbg/handler.ex"},{line,9}]},
{dbg,handle_traces,4,[{file,"dbg.erl"},{line,819}]},
{dbg,tracer_loop,2,[{file,"dbg.erl"},{line,783}]}]}}

[fishcakez]

Unfortunately this is due to a bug in Elixir 1.2.0. It is fixed in 1.3.0-dev and 1.2.1-dev. elixir-lang/elixir@a6b80a1