Try a fix for #127

lib/byebug/attacher.rb

@@ -6,13 +6,15 @@ module Byebug
   # Enters byebug right before (or right after if _before_ is false) return
   # events occur. Before entering byebug the init script is read.
   #
-  def self.attach(steps_out, before)
+  def self.attach
+    return errmsg('Byebug already started. Ignoring `byebug` call.') if started?
+
     setup_cmd_line_args
 
     start
     run_init_script
 
-    current_context.step_out(steps_out, before)
+    current_context.step_out(2, true)
   end
 end
 
@@ -22,8 +24,8 @@ def self.attach(steps_out, before)
 # Dropping a `byebug` call anywhere in your code, you get a debug prompt.
 #
 module Kernel
-  def byebug(steps_out = 1, before = true)
-    Byebug.attach(steps_out + 1, before)
+  def byebug
+    Byebug.attach
   end
 
   alias_method :debugger, :byebug

lib/byebug/commands/tracevar.rb

@@ -32,7 +32,8 @@ def execute
 
     def on_change(name, value, stop)
       puts pr('trace.messages.on_change', name: name, value: value)
-      byebug(1, false) if stop
+
+      @state.context.step_out(1, false) if stop
     end
 
     class << self

test/commands/eval_test.rb

@@ -111,8 +111,10 @@ module Byebug
           # Toy class to test evaluation in Byebug's prompt
           #
           class #{example_class}
+            attr_accessor :thread
+
             def initialize
-              Thread.new do
+              @thread = Thread.new do
                 loop do
                   sleep 0.01
                   next if numbers.empty?
@@ -144,7 +146,7 @@ def calc(number)
 
           byebug
 
-          'Processed: ' + worker.squares.join(' ')
+          worker.thread.kill
         end
       EOC
     end

test/support/test_case.rb

@@ -50,6 +50,7 @@ def setup
     def teardown
       cleanup_namespace
       clear_example_file
+      Byebug.stop
     end
 
     #