[glibmm] DBus::Connection: Pass an empty bus name as nullptr

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 843547cfe72de8958b7cdd5cc1a3390fc5102657
Author: Kjell Ahlstedt <kjell ahlstedt bredband net>
Date:   Thu Feb 4 16:37:08 2016 +0100

    DBus::Connection: Pass an empty bus name as nullptr
    
    * gio/src/dbusconnection.[hg|ccg]: Some string parameters in some C functions
    accept nullptr, others don't.
    call(), call_sync(): bus_name: Pass nullptr for an empty string.
    emit_signal(): Only destination_bus_name can be nullptr.
                   Other string parameters: Pass c_str().
    The bug in call() and call_sync() was noticed by Gerlof Fokkema on gtkmm-list.
    The bug in emit_signal() is an overreaction to bug 645072. All string
    parameters were changed to pass nullptr, but only destination_bus_name
    should have been changed.

 gio/src/dbusconnection.ccg |   23 ++++++++++-------------
 gio/src/dbusconnection.hg  |   12 +++++-------
 2 files changed, 15 insertions(+), 20 deletions(-)
---
diff --git a/gio/src/dbusconnection.ccg b/gio/src/dbusconnection.ccg
index 113a775..a2f67b3 100644
--- a/gio/src/dbusconnection.ccg
+++ b/gio/src/dbusconnection.ccg
@@ -635,7 +635,7 @@ void Connection::call(
   // and deleted in the callback.
   auto slot_copy = new SlotAsyncReady(slot);
 
-  g_dbus_connection_call(gobj(), bus_name.c_str(), object_path.c_str(),
+  g_dbus_connection_call(gobj(), Glib::c_str_or_nullptr(bus_name), object_path.c_str(),
     interface_name.c_str(), method_name.c_str(),
     const_cast<GVariant*>(parameters.gobj()), reply_type.gobj(),
     static_cast<GDBusCallFlags>(flags), timeout_msec,
@@ -659,7 +659,7 @@ void Connection::call(
   // and deleted in the callback.
   auto slot_copy = new SlotAsyncReady(slot);
 
-  g_dbus_connection_call(gobj(), bus_name.c_str(), object_path.c_str(),
+  g_dbus_connection_call(gobj(), Glib::c_str_or_nullptr(bus_name), object_path.c_str(),
     interface_name.c_str(), method_name.c_str(),
     const_cast<GVariant*>(parameters.gobj()), reply_type.gobj(),
     static_cast<GDBusCallFlags>(flags), timeout_msec, nullptr,
@@ -680,7 +680,7 @@ Glib::VariantContainerBase Connection::call_sync(
   GError* gerror = nullptr;
 
   GVariant* const gvariant =
-    g_dbus_connection_call_sync(gobj(), bus_name.c_str(), object_path.c_str(),
+    g_dbus_connection_call_sync(gobj(), Glib::c_str_or_nullptr(bus_name), object_path.c_str(),
     interface_name.c_str(), method_name.c_str(),
     const_cast<GVariant*>(parameters.gobj()), reply_type.gobj(),
     static_cast<GDBusCallFlags>(flags), timeout_msec,
@@ -706,7 +706,7 @@ Glib::VariantContainerBase Connection::call_sync(
   GError* gerror = nullptr;
 
   GVariant* const gvariant =
-    g_dbus_connection_call_sync(gobj(), bus_name.c_str(), object_path.c_str(),
+    g_dbus_connection_call_sync(gobj(), Glib::c_str_or_nullptr(bus_name), object_path.c_str(),
     interface_name.c_str(), method_name.c_str(),
     const_cast<GVariant*>(parameters.gobj()), reply_type.gobj(),
     static_cast<GDBusCallFlags>(flags), timeout_msec, nullptr, &gerror);
@@ -737,7 +737,7 @@ void Connection::call(
   // and deleted in the callback.
   auto slot_copy = new SlotAsyncReady(slot);
 
-  g_dbus_connection_call_with_unix_fd_list(gobj(), bus_name.c_str(),
+  g_dbus_connection_call_with_unix_fd_list(gobj(), Glib::c_str_or_nullptr(bus_name),
     object_path.c_str(), interface_name.c_str(), method_name.c_str(),
     const_cast<GVariant*>(parameters.gobj()), reply_type.gobj(),
     static_cast<GDBusCallFlags>(flags), timeout_msec, Glib::unwrap(fd_list),
@@ -762,7 +762,7 @@ void Connection::call(
   // and deleted in the callback.
   auto slot_copy = new SlotAsyncReady(slot);
 
-  g_dbus_connection_call_with_unix_fd_list(gobj(), bus_name.c_str(),
+  g_dbus_connection_call_with_unix_fd_list(gobj(), Glib::c_str_or_nullptr(bus_name),
     object_path.c_str(), interface_name.c_str(), method_name.c_str(),
     const_cast<GVariant*>(parameters.gobj()), reply_type.gobj(),
     static_cast<GDBusCallFlags>(flags), timeout_msec, Glib::unwrap(fd_list),
@@ -779,15 +779,12 @@ void Connection::emit_signal(
 {
   GError* gerror = nullptr;
 
-  // Strings are checked to see if they are empty so that nullptr can be passed
-  // for those strings to the C API.  This is done because some strings such as
-  // the bus name can be nullptr in the C API meaning that the signal should be
-  // emitted to all the listeners.
+  // destination_bus_name is checked to see if it is empty so that nullptr can be passed
+  // to the C API. This is done because the bus name can be nullptr in the C API,
+  // meaning that the signal should be emitted to all the listeners.
   g_dbus_connection_emit_signal(gobj(),
     Glib::c_str_or_nullptr(destination_bus_name),
-    Glib::c_str_or_nullptr(object_path),
-    Glib::c_str_or_nullptr(interface_name),
-    Glib::c_str_or_nullptr(signal_name),
+    object_path.c_str(), interface_name.c_str(), signal_name.c_str(),
     const_cast<GVariant*>(parameters.gobj()), &gerror);
 
   if(gerror)
diff --git a/gio/src/dbusconnection.hg b/gio/src/dbusconnection.hg
index 065db96..ff226fd 100644
--- a/gio/src/dbusconnection.hg
+++ b/gio/src/dbusconnection.hg
@@ -1,5 +1,3 @@
-// -*- Mode: C++; indent-tabs-mode: nil; c-basic-offset: 2 -*-
-
 /* Copyright (C) 2010 The giomm Development Team
  *
  * This library is free software; you can redistribute it and/or
@@ -627,7 +625,7 @@ public:
    * method or <tt>0</tt> if not passing parameters.
    * @param slot A SlotAsyncReady to call when the request is satisfied.
    * @param cancellable A Cancellable.
-   * @param bus_name A unique or well-known bus name or <tt>0</tt> if the
+   * @param bus_name A unique or well-known bus name or an empty string if the
    * connection is not a message bus connection.
    * @param timeout_msec The timeout in milliseconds, -1 to use the default
    * timeout or G_MAXINT for no timeout.
@@ -693,7 +691,7 @@ public:
    * @param parameters A Glib::VariantContainerBase tuple with parameters for the
    * method or <tt>0</tt> if not passing parameters.
    * @param cancellable A Cancellable.
-   * @param bus_name A unique or well-known bus name or <tt>0</tt> if the
+   * @param bus_name A unique or well-known bus name or an empty string if the
    * connection is not a message bus connection.
    * @param timeout_msec The timeout in milliseconds, -1 to use the default
    * timeout or G_MAXINT for no timeout.
@@ -744,7 +742,7 @@ public:
    * @param slot A SlotAsyncReady to call when the request is satisfied.
    * @param cancellable A Cancellable.
    * @param fd_list A UnixFDList.
-   * @param bus_name A unique or well-known bus name or <tt>0</tt> if the
+   * @param bus_name A unique or well-known bus name or an empty string if the
    * connection is not a message bus connection.
    * @param timeout_msec The timeout in milliseconds, -1 to use the default
    * timeout or G_MAXINT for no timeout.
@@ -801,7 +799,7 @@ public:
       const Glib::RefPtr<Cancellable>&    cancellable{.?},
       const Glib::RefPtr<UnixFDList>&     fd_list{.},
       Glib::RefPtr<UnixFDList>&           out_fd_list{.>>},
-      const Glib::ustring&                bus_name{.} = Glib::ustring(),
+      const Glib::ustring&                bus_name{.NULL} = Glib::ustring(),
       int                                 timeout_msec{.} = -1,
       CallFlags                           flags{.} = Gio::DBus::CALL_FLAGS_NONE,
       const Glib::VariantType&            reply_type{.} = Glib::VariantType()
@@ -818,7 +816,7 @@ public:
    * @param interface_name D-Bus interface to emit a signal on.
    * @param signal_name The name of the signal to emit.
    * @param destination_bus_name The unique bus name for the destination for
-   * the signal or <tt>0</tt> to emit to all listeners.
+   * the signal or an empty string to emit to all listeners.
    * @param parameters A Glib::VariantContainerBase tuple with parameters for the
    * signal or <tt>0</tt> if not passing parameters.
    * @throw Glib::Error.