When calling `g_set_object()` for a type derived from `GObject`, GCC 9.2
was giving the following strict aliasing warning:
```
../../source/malcontent/libmalcontent-ui/user-controls.c:1001:21: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
1001 | if (g_set_object (&self->user, user))
/opt/gnome/install/include/glib-2.0/gobject/gobject.h:744:33: note: in definition of macro ‘g_set_object’
744 | (g_set_object) ((GObject **) (object_ptr), (GObject *) (new_object)) \
| ^~~~~~~~~~
```
This was due to the `(GObject **)` cast.
Pass the pointer through a union to squash this warning. We already do
some size and type checks of the dereferenced type, which should catch
casual errors. The `g_object_ref()` and `g_object_unref()` calls which
subsequently happen inside the `g_set_object()` function also do some
dynamic type checks.
Add a test.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
The implementation is silently discarding this anyway, and
g_object_unref() is using atomic operations. So this should be safe.
Having this here triggers -Wdiscarded-qualifiers when g_clear_pointer()
is fixed to use __typeof__().
The implementation is silently discarding this anyway, and
g_object_unref() is using atomic operations. So this should be safe.
Having this here triggers -Wdiscarded-qualifiers when g_clear_pointer()
is fixed to use __typeof__().
Switch the check which tests whether the object has been finalised from
being a use-after-free, to using a weak pointer which is nullified on
finalisation.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
Weak-pointers are currently lacking g_set_object() & g_clear_object()
helpers equivalent. New functions (and macros, both are provided) are
convenient in many case, especially for the property's notify-on-set
pattern:
if (g_set_weak_pointer (...))
g_object_notify (...)
Inspired by Christian Hergert's original implementation for
gnome-builder.
https://bugzilla.gnome.org/show_bug.cgi?id=749527
Along the same lines as g_clear_object(), g_set_object() is a
convenience function to update a GObject pointer, handling reference
counting transparently and correctly.
Specifically, it handles the case where a pointer is set to its current
value. If handled naïvely, that could result in the object instance
being finalised. In the following code, that happens when
(my_obj == new_value) and the object has a single reference:
g_clear_object (&my_obj);
my_obj = g_object_ref (new_value);
It also simplifies boilerplate code such as set_property()
implementations, which are otherwise long and boring.
Test cases included.
https://bugzilla.gnome.org/show_bug.cgi?id=741589
Very many testcases, some GLib tools (resource compiler, etc) and
GApplication were calling g_type_init().
Remove those uses, as they are no longer required.
https://bugzilla.gnome.org/show_bug.cgi?id=686161
