timeout.rb: defer creating custom exception

* lib/timeout.rb (Timeout#timeout): when a custom exception is given,
  no instance is needed to be caught, so defer creating new instance
  until it is raised.  [ruby-core:59511] [Bug ruby#9354]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44517 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

Conflicts:
	ChangeLog

Author: nobu

lib/timeout.rb

@@ -67,7 +67,7 @@ def timeout(sec, klass = nil)   #:yield: +sec+
     return yield(sec) if sec == nil or sec.zero?
     message = "execution expired"
     e = Error
-    bt = catch((klass||ExitException).new) do |exception|
+    bl = proc do |exception|
       begin
         x = Thread.current
         y = Thread.start {
@@ -80,7 +80,7 @@ def timeout(sec, klass = nil)   #:yield: +sec+
           end
         }
         return yield(sec)
-      rescue (klass||ExitException) => e
+      rescue klass => e
         e.backtrace
       ensure
         if y
@@ -89,6 +89,7 @@ def timeout(sec, klass = nil)   #:yield: +sec+
         end
       end
     end
+    bt = klass ? bl.call(klass) : catch((klass = ExitException).new, &bl)
     rej = /\A#{Regexp.quote(__FILE__)}:#{__LINE__-4}\z/o
     bt.reject! {|m| rej =~ m}
     level = -caller(CALLER_OFFSET).size

test/test_timeout.rb

@@ -57,4 +57,14 @@ def test_rescue_exit
     end
     assert_raise_with_message(exc, /execution expired/) {raise e if e}
   end
+
+  def test_custom_exception
+    bug9354 = '[ruby-core:59511] [Bug #9354]'
+    err = Class.new(StandardError) do
+      def initialize(msg) super end
+    end
+    assert_nothing_raised(ArgumentError, bug9354) do
+      assert_equal(:ok, timeout(100, err) {:ok})
+    end
+  end
 end