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[sigc] Invalidating parentless slots

  I got the attached message and (reversed) patch in the Debian BTS.

  Daniel

-- 
/------------------- Daniel Burrows <dburrows debian org> ------------------\
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--- Begin Message --- 
Package: libsigc++-2.0
Severity: normal
Tags: patch

sigc::slot can be used as a function pointer with the advantage of being
able to add function arguments with sigc::bind, etc.  However,
disconnecting such slots does not work, because it doesn't do anything
if there is no parent to notify.

In my programs it is quite usual that there isn't a parent, because I
know what happens to the slot, so I don't need a notification.  However,
I still need to invalidate the slot sometimes, and even
slot = sigc::slot0 <void> ();
doesn't work, because that simply calls disconnect ().

The attached patch invalidates the slot on disconnect, even if there is
no parent.

-- System Information:
Debian Release: testing/unstable
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: i386 (i686)
Shell:  /bin/sh linked to /bin/bash
Kernel: Linux 2.6.11
Locale: LANG=C, LC_CTYPE=C (charmap=ANSI_X3.4-1968)

--- slot_base.cc	2005-09-02 15:39:48.000000000 +0200
+++ libsigc++-2.0.10/sigc++/functors/slot_base.cc	2005-02-11 11:59:07.000000000 +0100
@@ -40,11 +40,11 @@ void slot_rep::operator delete(void* p)
 
 void slot_rep::disconnect()
 {
-  call_ = 0;            // Invalidate the slot.
-                        // _Must_ be done here because parent_ might defer the actual
-                        // destruction of the slot_rep and try to invoke it before that point.
   if (parent_)
   {
+    call_ = 0;          // Invalidate the slot.
+                        // _Must_ be done here because parent_ might defer the actual
+                        // destruction of the slot_rep and try to invoke it before that point.
     void* data_ = parent_;
     parent_ = 0;        // Just a precaution.
     (cleanup_)(data_);  // Notify the parent (might lead to destruction of this!).

--- End Message ---
--- Begin Message --- 
I just noticed the patch is reversed, so you need -R to apply it.  Sorry about
that.

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