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-rw-r--r--gio/giomm/socketsource.cc6
-rw-r--r--glib/glibmm/main.cc6
-rw-r--r--glib/glibmm/utility.h23
-rw-r--r--glib/src/optiongroup.ccg28
-rw-r--r--tests/glibmm_vector/main.cc4
5 files changed, 34 insertions, 33 deletions
diff --git a/gio/giomm/socketsource.cc b/gio/giomm/socketsource.cc
index 4485a996..e46af5dd 100644
--- a/gio/giomm/socketsource.cc
+++ b/gio/giomm/socketsource.cc
@@ -74,7 +74,7 @@ SignalSocket::connect(const sigc::slot<bool(Glib::IOCondition)>& slot,
g_socket_create_source(socket->gobj(), (GIOCondition)condition, Glib::unwrap(cancellable));
return Glib::Source::attach_signal_source(
slot, priority, source, context_,
- Glib::bitwise_equivalent_cast<GSourceFunc>(&giomm_signalsocket_callback));
+ Glib::function_pointer_cast<GSourceFunc>(&giomm_signalsocket_callback));
}
SignalSocket
@@ -105,7 +105,7 @@ SocketSource::SocketSource(const Glib::RefPtr<Socket>& socket, Glib::IOCondition
const Glib::RefPtr<Cancellable>& cancellable)
: IOSource(
g_socket_create_source(socket->gobj(), (GIOCondition)condition, Glib::unwrap(cancellable)),
- Glib::bitwise_equivalent_cast<GSourceFunc>(&giomm_socketsource_callback))
+ Glib::function_pointer_cast<GSourceFunc>(&giomm_socketsource_callback))
{
}
@@ -113,7 +113,7 @@ SocketSource::SocketSource(GSocket* socket, Glib::IOCondition condition,
const Glib::RefPtr<Cancellable>& cancellable)
: IOSource(
g_socket_create_source(socket, (GIOCondition)condition, Glib::unwrap(cancellable)),
- Glib::bitwise_equivalent_cast<GSourceFunc>(&giomm_socketsource_callback))
+ Glib::function_pointer_cast<GSourceFunc>(&giomm_socketsource_callback))
{
}
diff --git a/glib/glibmm/main.cc b/glib/glibmm/main.cc
index 15200099..e4095405 100644
--- a/glib/glibmm/main.cc
+++ b/glib/glibmm/main.cc
@@ -508,7 +508,7 @@ SignalChildWatch::connect(const sigc::slot<void(GPid, int)>& slot, GPid pid, int
if (priority != G_PRIORITY_DEFAULT)
g_source_set_priority(source, priority);
- g_source_set_callback(source, Glib::bitwise_equivalent_cast<GSourceFunc>(&glibmm_child_watch_callback),
+ g_source_set_callback(source, Glib::function_pointer_cast<GSourceFunc>(&glibmm_child_watch_callback),
conn_node,
&glibmm_source_destroy_notify_callback);
@@ -1232,13 +1232,13 @@ IOSource::IOSource(PollFD::fd_t fd, IOCondition condition) : poll_fd_(fd, condit
IOSource::IOSource(const Glib::RefPtr<IOChannel>& channel, IOCondition condition)
: Source(g_io_create_watch(channel->gobj(), (GIOCondition)condition),
- Glib::bitwise_equivalent_cast<GSourceFunc>(&glibmm_iosource_callback))
+ Glib::function_pointer_cast<GSourceFunc>(&glibmm_iosource_callback))
{
}
IOSource::IOSource(GIOChannel* channel, IOCondition condition)
: Source(g_io_create_watch(channel, (GIOCondition)condition),
- Glib::bitwise_equivalent_cast<GSourceFunc>(&glibmm_iosource_callback))
+ Glib::function_pointer_cast<GSourceFunc>(&glibmm_iosource_callback))
{
}
diff --git a/glib/glibmm/utility.h b/glib/glibmm/utility.h
index da23272c..6c7378af 100644
--- a/glib/glibmm/utility.h
+++ b/glib/glibmm/utility.h
@@ -96,20 +96,23 @@ destroy_notify_delete(void* data)
// Conversion between different types of function pointers with
// reinterpret_cast can make gcc8 print a warning.
// https://github.com/libsigcplusplus/libsigcplusplus/issues/1
-/** Returns the supplied bit pattern, interpreted as another type.
+// https://github.com/libsigcplusplus/libsigcplusplus/issues/8
+/** Returns the supplied function pointer, cast to a pointer to another function type.
*
- * When reinterpret_cast causes a compiler warning or error, this function
- * may work. Intended mainly for conversion between different types of pointers.
+ * When a single reinterpret_cast between function pointer types causes a
+ * compiler warning or error, this function may work.
+ *
+ * Qualify calls with namespace names: sigc::internal::function_pointer_cast<>().
+ * If you don't, indirect calls from another library that also contains a
+ * function_pointer_cast<>() (perhaps glibmm), can be ambiguous due to ADL
+ * (argument-dependent lookup).
*/
template <typename T_out, typename T_in>
-inline T_out bitwise_equivalent_cast(T_in in)
+inline T_out function_pointer_cast(T_in in)
{
- union {
- T_in in;
- T_out out;
- } u;
- u.in = in;
- return u.out;
+ // The double reinterpret_cast suppresses a warning from gcc8 with the
+ // -Wcast-function-type option.
+ return reinterpret_cast<T_out>(reinterpret_cast<void (*)()>(in));
}
} // namespace Glib
diff --git a/glib/src/optiongroup.ccg b/glib/src/optiongroup.ccg
index b14d7b31..ee9b7bfe 100644
--- a/glib/src/optiongroup.ccg
+++ b/glib/src/optiongroup.ccg
@@ -552,22 +552,20 @@ OptionGroup::CppOptionEntry::allocate_c_arg()
case G_OPTION_ARG_CALLBACK:
{
// The C arg pointer is a function pointer, cast to void*.
- carg_ = Glib::bitwise_equivalent_cast<void*>(&OptionGroup::option_arg_callback);
-
- // With all compiler warnings turned on and a high optimization level
- // it's difficult to cast a function pointer to a void*. See bug 589197.
- // A few results with g++ 4.4.5 with the flags -pedantic -O2 -Werror:
- //
- // carg_ = reinterpret_cast<void*>(&OptionGroup::option_arg_callback);
- // error: ISO C++ forbids casting between pointer-to-function and pointer-to-object
- //
- // *reinterpret_cast<GOptionArgFunc*>(&carg_) = &OptionGroup::option_arg_callback;
- // *(OptionArgFunc*)&carg_ = &OptionGroup::option_arg_callback;
- // error: dereferencing type-punned pointer will break strict-aliasing rules
//
- // If any compiler dislikes the union, the following code is worth testing:
- // carg_ = reinterpret_cast<void*>(
- // reinterpret_cast<unsigned long>(&OptionGroup::option_arg_callback));
+ // carg_ = reinterpret_cast<void*>(&OptionGroup::option_arg_callback);
+ // or
+ // union {
+ // void* dp;
+ // GOptionArgFunc fp;
+ // } u;
+ // u.fp = &OptionGroup::option_arg_callback;
+ // carg_ = u.dp;
+ // ? See
+ // https://bugzilla.gnome.org/show_bug.cgi?id=589197
+ // https://github.com/libsigcplusplus/libsigcplusplus/issues/1
+ // https://github.com/libsigcplusplus/libsigcplusplus/issues/8
+ carg_ = reinterpret_cast<void*>(&OptionGroup::option_arg_callback);
break;
}
diff --git a/tests/glibmm_vector/main.cc b/tests/glibmm_vector/main.cc
index dd83553e..a3719532 100644
--- a/tests/glibmm_vector/main.cc
+++ b/tests/glibmm_vector/main.cc
@@ -198,12 +198,12 @@ public:
{
if (glist_)
{
- g_list_foreach(glist_, Glib::bitwise_equivalent_cast<GFunc>(g_object_unref), nullptr);
+ g_list_foreach(glist_, Glib::function_pointer_cast<GFunc>(g_object_unref), nullptr);
g_list_free(glist_);
}
if (gslist_)
{
- g_slist_foreach(gslist_, Glib::bitwise_equivalent_cast<GFunc>(g_object_unref), nullptr);
+ g_slist_foreach(gslist_, Glib::function_pointer_cast<GFunc>(g_object_unref), nullptr);
g_slist_free(gslist_);
}
if (garray_)
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