Add ChildProcess.close_on_exec helper to work around #1.

lib/childprocess.rb

@@ -1,6 +1,7 @@
 require 'childprocess/errors'
 require 'childprocess/abstract_process'
 require 'childprocess/abstract_io'
+require "fcntl"
 
 module ChildProcess
   autoload :Unix,     'childprocess/unix'
@@ -67,6 +68,21 @@ def os
         end
       )
     end
+
+    #
+    # By default, a child process will inherit open files and sockets from the parent process.
+    # This helper provides a cross-platform way of making sure that doesn't happen for the given file.
+    # 
 
-  end
-end
+    def close_on_exec(file)
+      if windows?
+        Windows.dont_inherit file
+      elsif file.respond_to?(:fcntl) && defined?(Fcntl::FD_CLOEXEC)
+        file.fcntl Fcntl::F_SETFD, Fcntl::FD_CLOEXEC
+      else
+        raise Error, "not sure how to set close-on-exec for #{file.inspect} on #{platform}"
+      end
+    end
+
+  end # class << self
+end # ChildProcess

lib/childprocess/windows/api.rb

@@ -28,6 +28,17 @@ def waitpid2(pid, flags = 0)
         [pid, code] if code
       end
 
+      def dont_inherit(file)
+        unless file.respond_to?(:fileno)
+          raise ArgumentError, "expected #{file.inspect} to respond to :fileno"
+        end
+
+        handle = Lib.get_os_file_handle(file.fileno)
+
+        ok = Lib.set_handle_information(handle, HANDLE_FLAG_INHERIT, 0)
+        ok or raise Error, Lib.last_error_message
+      end
+
       private
 
       def no_hang?(flags)

lib/childprocess/windows/constants.rb

@@ -21,7 +21,7 @@ module ChildProcess::Windows
 
   STARTF_USESTDHANDLES          = 0x00000100
   INVALID_HANDLE_VALUE          = 0xFFFFFFFF
-
+  HANDLE_FLAG_INHERIT           = 0x00000001
 
   module Lib
     enum :wait_status, [ :wait_object_0,  0,

lib/childprocess/windows/functions.rb

@@ -8,7 +8,7 @@ def self.create_proc(cmd, opts = {})
         flags   = 0
         inherit = !!opts[:inherit]
 
-        flags  |= DETACHED_PROCESS if opts[:detach]
+        flags |= DETACHED_PROCESS if opts[:detach]
 
         si = StartupInfo.new
         pi = ProcessInfo.new
@@ -183,6 +183,14 @@ def self.get_os_file_handle(fd_or_io)
 
       attach_function :_get_osfhandle, :_get_osfhandle, [:int], :long
 
+      # BOOL WINAPI SetHandleInformation(
+      #   __in  HANDLE hObject,
+      #   __in  DWORD dwMask,
+      #   __in  DWORD dwFlags
+      # );
+
+      attach_function :set_handle_information, :SetHandleInformation, [:long, :ulong, :ulong], :bool
+
     end # Lib
   end # Windows
 end # ChildProcess

spec/childprocess_spec.rb

@@ -96,4 +96,17 @@
     end
   end
 
+  it "can set close-on-exec when IO is inherited" do
+    server = TCPServer.new("localhost", 4433)
+    ChildProcess.close_on_exec server
+
+    process = sleeping_ruby
+    process.io.inherit!
+
+    process.start
+    server.close
+
+    lambda { TCPServer.new("localhost", 4433).close }.should_not raise_error
+  end
+
 end

spec/spec_helper.rb

@@ -1,9 +1,11 @@
 $LOAD_PATH.unshift(File.dirname(__FILE__))
 $LOAD_PATH.unshift(File.join(File.dirname(__FILE__), '..', 'lib'))
+
 require 'childprocess'
 require 'spec'
 require 'spec/autorun'
 require 'tempfile'
+require "socket"
 
 module ChildProcessSpecHelper
   RUBY = defined?(Gem) ? Gem.ruby : 'ruby'