Coverity notices the `g_object_unref()` call in `g_object_notify()`, but
not the paired `g_object_ref()` call. It therefore incorrectly assumes
that every call to `g_object_notify()` frees the object. This causes a
lot (hundreds) of false positive reports about double-frees or
use-after-frees.
I can’t find a way to fix this using a model file, so the other options
are:
* Manually mark every report as a false positive and keep updating them
as the code changes over time. This would take a lot of maintainer
effort.
* Comment out the `g_object_ref()`/`g_object_unref()` calls when
running static analysis (but not in a normal production build). This
is ugly, but cheap and shouldn’t impact maintainability much.
So this commit implements option 2.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
We need to match the conditions in g_object_init
for when we already have a freeze. Without that,
we underflow the freeze count and trigger a
warning.
Fixes: #2666
When the param specs are provided as an array
with g_object_class_install_properties, keep
a copy of that array around and use it for
looking up properties without the param spec
pool.
Note that this is an opportunistic optimization -
currently, it only works for properties of the
class itself, not for parent classes, and it
only works if the property names are identical
string literals (we're at the mercy of the linker
for that).
If we don't get lucky, we fall back to using
the pspec pool as usual.
This may fix Coverity assuming that pspecs are leaked, which is causing
tens and tens of false positives in the latest Coverity reports for
GLib.
Ensure that the pspecs are sunk (if floating) even if adding them to the
class fails (due to validation failure or an identically named property
already existing).
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
If we have no nontrivial notify vfunc, and no signal
handlers for notify, we don't need to maintain the
notify queue. No need to notify if nobody's listening.
Check whether an object has a nontrivial notify vfunc
and avoid creating and updating the notify queue if
it doesn't. We know that there can be no notify signal
handlers at this point. No need to notify if nobody's
listening.
We currently keep a flag for whether an object has
ever had any signal handlers. But even if it had signal
handlers, it may not have any notify handlers. Keep that
information separately, so we can speed up property setting.
According to the commit that introduced these
calls (4b334ef8f1), we are checking
the refcount here to avoid calling g_object_ref
when the refcount is 0, in the rare case that
notification would be triggered during finalize.
But we are now freezing notifications during
finalize, and after recent changes, we no longer call
g_object_ref for notification while a freeze is
in place.
We only need to take a ref on the object when
we call out to external code (ie around
->dispatch_properties_changed). If we avoid
the signal emission, we can avoid the ref/unref
too. This is not currently happening, but
might in the future.
A small reorg that reduces the code and matches
what we do for object_get_property.
Note that as a consequence of this change, we now
check the deprecated flag on the redirected property,
not on the original when setting properties. This
matches what we were already doing for getting
properties.
The code that emits property deprecation warnings
rarely runs, and doesn't need to be inlined
everywhere. It is enough to inline the check for
the deprecation flag.
It is safe not to copy arguments here,
because we are not emitting any signals
before we are done setting the values
as properties.
This matches what we do for g_object_new now.
We can safely use the values without copying here.
This is safe because we are not emitting any
signals before we are done setting the values
as properties.
This avoids walking the construct params list
one extra time just to count when constructing
objects, for a small speedup of object construction
in the presence of construct params.
Avoid GValue transformation when we can, using
the new value_is_valid vfunc.
This is particularly useful for string properties,
where g_value_transform will make a copy of the string.
In several places we do paired calls of g_value_init
and g_value_unset, both of which peek the value table.
We can avoid half of that cost by remembering the value
table, instead of looking it up again.
This uses the new G_VALUE_COLLECT_INIT2 macro.
Drop the redundant `PROP_0` (which isn’t a real property) and initialise
the first member of the enum instead.
Add a typedef so that the enum type can be used in `switch` statements
in `get_property()` and `set_property()` vfuncs. This allows
`-Wswitch-enum` to be used to improve type safety.
The examples here don’t have `get_property()` or `set_property()`
vfuncs, but people might copy/paste the code to somewhere which does.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
Make it a bit clearer in the documentation that using
`G_PARAM_STATIC_STRINGS` everywhere is a good thing.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
Notifying during object destruction is a dubious "feature": objects
might end up recreating a bunch of state just before clearing it;
language bindings might get spurious notifications during garbage
collection runs.
We freeze the notification queue before running the dispose() chain; if
the object was temporarily vivified during dispose, we thaw the
notification queue, otherwise we let the instance clear it when we
finalize it.
See: https://gitlab.gnome.org/GNOME/gjs/-/issues/445
We now guarantee that GObjects will always be allocated at least as
aligned as the basic types. If you want to put an element in your
GObject which has higher alignment requirements, we can’t guarantee it
will be aligned*. If you need it to be aligned, you’ll need to put it on
the heap (aligned appropriately), or add appropriate padding in your
GObject struct.
*Actually, GSlice will guarantee that the whole GObject is aligned to at
least the power of 2 greater than or equal to the size of the GObject,
which means any element in the GObject struct should always be
appropriate aligned if the compiler pads it appropriately. If malloc()
is used, however, it doesn’t make that guarantee, so we can’t make that
guarantee overall.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
Helps: #1231
See the reasoning in the patch for why we believe GObjects *are*
(already) as aligned as the basic types.
We want to make this guarantee so that it’s guaranteed to be safe for
people to ignore -Wcast-align warnings for GObjects which contain basic
types. This typically happens with gdouble on 32-bit ARM platforms.
The checks are slightly complicated by the need to support GObjects with
custom constructors. We should expect that a custom construction
function will chain up to g_object_constructor (which calls
g_type_create_instance() as normal), but it’s possible that someone has
done something crazy and uses a custom allocator which doesn’t return
with the same alignment as GSlice. Hand them a warning in that case. If
that is true, the code which uses their custom-constructed GObject can
presumably already deal with the alignment it gets given.
Signed-off-by: Philip Withnall <withnall@endlessm.com>
Helps: #1231
When an object with toggle reference is notifying a change we just
assume that this is true because of previous checks.
However, while locking, another thread may have removed the toggle
reference causing the waiting thread to abort (as no handler is set at
that point).
To avoid this, once we've got the toggle references mutex lock, check
again if the object has toggle reference, and if it's not the case
anymore just ignore the request.
Add a test that triggers this, it's not 100% happening because this is
of course timing related, but this is very close to the truth.
Fixes: #2394
The previous wording was not clear about what happens if a new weak ref
is taken during disposal (shortly after resurrecting the object with a
new strong ref, otherwise taking the weak ref is invalid).
See: https://gitlab.gnome.org/GNOME/glib/-/merge_requests/2064/diffs#note_1270092
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
Helps: #2390
No need to call memset in the loop, we can just
initialize all the values in one go.
GtkBuilder is now using g_object_setv, so this
may improve application start times a bit.
As per the previous change, an object that had weak locations set may
need to lock again the weak locations mutex during qdata cleanup, but
we can avoid this when we know we're removing the last location, by
removing the qdata entry and freeing the data.
In case a new location is needed for the same object, new data will be
added.
However, by doing this the weak locations during dispose may be
invalidated once the weak locations lock is passed, so check again if
this is the case while removing them.
