[glibmm] IOChannel: Avoid creating a RefPtr to this.

[Murray Cumming <murrayc src gnome org>]

commit 04f14381a5fcefa3cf78d792c604318ffed81427
Author: Murray Cumming <murrayc murrayc com>
Date:   Wed Apr 5 12:23:49 2017 +0200

    IOChannel: Avoid creating a RefPtr to this.
    
    By adding a private IOSource constructor (and create()), accessible
    via a friend declaration, that takes the raw GIOChannel.
    
    See https://bugzilla.gnome.org/show_bug.cgi?id=755037#c20

 glib/glibmm/main.cc    |   12 ++++++++++++
 glib/glibmm/main.h     |    8 ++++++++
 glib/src/iochannel.ccg |    5 +----
 3 files changed, 21 insertions(+), 4 deletions(-)
---
diff --git a/glib/glibmm/main.cc b/glib/glibmm/main.cc
index 1f19f46..36317f8 100644
--- a/glib/glibmm/main.cc
+++ b/glib/glibmm/main.cc
@@ -1231,6 +1231,12 @@ IOSource::create(const Glib::RefPtr<IOChannel>& channel, IOCondition condition)
   return Glib::RefPtr<IOSource>(new IOSource(channel, condition));
 }
 
+Glib::RefPtr<IOSource>
+IOSource::create(GIOChannel* channel, IOCondition condition)
+{
+  return Glib::RefPtr<IOSource>(new IOSource(channel, condition));
+}
+
 sigc::connection
 IOSource::connect(const sigc::slot<bool(IOCondition)>& slot)
 {
@@ -1248,6 +1254,12 @@ IOSource::IOSource(const Glib::RefPtr<IOChannel>& channel, IOCondition condition
 {
 }
 
+IOSource::IOSource(GIOChannel* channel, IOCondition condition)
+: Source(g_io_create_watch(channel, (GIOCondition)condition),
+    (GSourceFunc)&glibmm_iosource_callback)
+{
+}
+
 IOSource::IOSource(GSource* cast_item, GSourceFunc callback_func) : Source(cast_item, callback_func)
 {
 }
diff --git a/glib/glibmm/main.h b/glib/glibmm/main.h
index 63b1ef1..4252103 100644
--- a/glib/glibmm/main.h
+++ b/glib/glibmm/main.h
@@ -870,6 +870,14 @@ protected:
   bool dispatch(sigc::slot_base* slot) override;
 
 private:
+  friend IOChannel;
+
+  // This is just to avoid the need for Gio::Socket to create a RefPtr<> to itself.
+  static Glib::RefPtr<IOSource> create(GIOChannel* channel, IOCondition condition);
+
+  // This is just to avoid the need for Gio::Socket to create a RefPtr<> to itself.
+  IOSource(GIOChannel* channel, IOCondition condition);
+
   PollFD poll_fd_;
 };
 
diff --git a/glib/src/iochannel.ccg b/glib/src/iochannel.ccg
index 93b5725..1a97d0d 100644
--- a/glib/src/iochannel.ccg
+++ b/glib/src/iochannel.ccg
@@ -276,10 +276,7 @@ IOChannel::get_line_term() const
 Glib::RefPtr<IOSource>
 IOChannel::create_watch(IOCondition condition)
 {
-  // The corresponding unreference() takes place in the dtor
-  // of the Glib::RefPtr<IOChannel> object below.
-  reference();
-  return IOSource::create(Glib::RefPtr<IOChannel>(this), condition);
+  return IOSource::create(gobj(), condition);
 }
 
 void