The reason we need to enforce this is that the GTypeValueTable
documentation explicitly states that memory is memset to 0 when the
value_init function is called.
https://bugzilla.gnome.org/show_bug.cgi?id=603590
Makes g_signal_emit_valist from 15% to 20% faster.
Results reported from profiling the pan newsreader which uses a variant
of simple and complex signal emissions (i.e no args or various args)
https://bugzilla.gnome.org/show_bug.cgi?id=603590
Most callers of G_VALUE_COLLECT previously had to initialize the GValue
and then G_VALUE_COLLECT would still go through a cleanup phase.
The new variant allows passing a unitialized GValue along with a GType
and speedup the initialization/collection process.
https://bugzilla.gnome.org/show_bug.cgi?id=603590
If threads are available we always enable threads in gobject, which
means all gio/gobject code can enable the unconditional thread calls.
This is a minor optimization since we avoid a bunch of unnecessary
is-threads-enabled checks.
https://bugzilla.gnome.org/show_bug.cgi?id=606775
This works around the need to take a custom mutex twice and add the
object to a GSList of objects that are currently in construction for the
common case. Only when the constructor is overwritten do we use the
previous behavior and allow things like singleton objects.
The only slightly incompatible change is that previously, it was ok to
call g_object_set() on construct-only properties while the object was
initialized. This will now fail. If that behavior is needed, setting a
custom constructor that just chains up will reenable this functionality.
https://bugzilla.gnome.org/show_bug.cgi?id=557151
g_type_default_interface_peek() and g_type_value_table_peek() don't need
to acquire read locks anymore when they test the refcount instead of
node->data.
The function returns TRUE if the type was previously initialized and can
be easily reused. It returns FALSE and does not take a reference if the
type is not referenced yet.
g_type_class_ref() uses this to avoid taking locks in the common path,
which speeds up object creation a lot - in particular in multithreaded
applications.
https://bugzilla.gnome.org/show_bug.cgi?id=585375
This does not change any locking behavior at all, it just replaces
simple getters/setters of the variable with atomic versions.
The ref_count variable was kept as unsigned, even though that requires
casting for all operations, to mirror GObject->refcount.
https://bugzilla.gnome.org/show_bug.cgi?id=585375
Currently interface lookups are do a binary search over all the interfaces
an object implements. Its possible to do this lookup in constant time using for
instance the gcj algorighm described at:
http://gcc.gnu.org/ml/java/1999-q3/msg00377.html
This is an implementation of that based on GAtomicArray.
We implement lock free interface lookup by moving the n_ifaces
counter into memory pointed to by TypeNode->iface_entries, and
then updating this in RCU-style by always copying it, modifying
the copy and then when the modification is done replace the old
pointer with g_atomic_pointer_set.
There is one additional complexity when freeing the old memory,
since the old memory region can be in use. To handle this we
don't free such memory, but put it on a free list and reuse it
later. This means that lock-free lookups must be able to
handle the memory being modified in random ways without crashing,
and at the end we verify that the memory didn't change and the
transaction is ok.
With this infrastructure the patch then implements a lock-free
version of type_lookup_iface_entry_L called type_lookup_iface_vtable_I
and use it in: g_type_interface_peek, g_type_interface_peek_parent
and type_node_check_conformities_UorL.
Using the performance tests from bug 557100 shows that the general
performance difference is negligible, but the lack of a lock for each
type check and interface vfunc call should greatly enhance threaded
scalability.
This adds supports for a lock-less a non-shrinking growable array.
You can use it to do reads using no locks, as long as your read-code
can handle that during the read transaction the object can be modified
by another writer (but it will not change size or be freed), and you
can only trust the result once the transaction has finished successfully.
This doesn't free things like RCU normally does, instead it pushes the
memory on a free list that is reused for other atomic arrays.
The n_children variable can be written when locked, while the n_supers
variable is read at any time. As they both share the same bytes,
accessing them is not threadsafe.
This patch puts them into different bytes.
Thanks to Xan Lopez and valgrind for noticing this.
Store whether the object has a toggleref before decrementing the
refcount to prevent race condition when two threads simultaneously
try to unref an object with a refcount of 2.
Patch by Antoine Tremblay.
https://bugzilla.gnome.org/show_bug.cgi?id=551706
This avoids a bunch of code and makes construction of simple objects
faster.
Object construction performance improvement:
Non-Threaded Threaded
Simple: 14% 5%
Complex: -1.1% -2.2%
Other tests stable.
https://bugzilla.gnome.org/show_bug.cgi?id=557100
If the class has no properties there could be no notification anyway.
This is an important optimization for construction of simple objects.
Object construction performance improvement:
Non-Threaded Threaded
Simple: 84% 91%
Complex: -1.4% -0.6%
Other tests stable.
https://bugzilla.gnome.org/show_bug.cgi?id=557100
This is both cleaner and faster (it avoids function calls and
zeroing the memory twice).
Object construction performance improvement:
Non-Threaded Threaded
Simple: 11% 1.3%
Complex: 8% 6%
Other tests stable.
https://bugzilla.gnome.org/show_bug.cgi?id=557100
Commit 789e260638 tried to add support for -?, but there is a typo
and instead -h was added when already present instead of -? for one
of the cases.
It works without this corrections, because all unrecognized options
trigger usage showing as well, but this is more correct.
This was bug 556706 originally.
Tools like clang fail to recognize that stanzas like
g_return_if_fail (GTK_IS_FOO (w)) guarantee w != NULL. By minimally
rewriting the type-checking macros, we can avoid these false positives.
Since @filename@ contains the full filename as given to the glib-mkenum
command, possibly including path elements (e.g. when using a non-srcdir
build), it is unsuitable to use in a #include statement in the generated
file if one wants to distribute it. This patch adds @basename@ which
expands to the base name of the input filename. Bug #587307.
Update various README files to refer to git instead of svn.
Add a README.commits that is pretty much a copy of the same file
in GTK+. Also discontinue ChangeLog files.
2009-03-13 Kristian Rietveld <kris@imendio.com>
* gsignal.c (signal_lookup_closure): when defaulting to the only
item in the array, check if this is indeed the default closure.
(patch by Tim Janik).
svn path=/trunk/; revision=7979
GLib users buildable with gcc 4.4. Patch by Jakub Jelinek.
* glib/gatomic.[hc]: Add G_GNUC_MAY_ALIAS to pointer arguments,
fix macro versions to only operate on objects of the same size.
* glib/gdataset.c:
* glib/gthread.[hc]:
* glib/gdatasetprivate.h: Remove unnecessary casts in
g_atomic_pointer_get calls.
svn path=/trunk/; revision=7875
* configure.in: Define an ENABLE_REGEX macro
* gobject/gboxed.c: Don't refer to g_regex_ref if ENABLE_REGEX
is not defined.
svn path=/trunk/; revision=7815
2009-01-02 Behdad Esfahbod <behdad@gnome.org>
Bug 565136 – Gobject's "notify" signal parameters are wrong in gtk-doc
Patch from Andrzej Zaborowski
* gobject.c (g_object_do_class_init): Fix param order in docs.
svn path=/trunk/; revision=7759
* gtypemodule.c (g_type_module_use): Always reset the use count
to its previous value before returning FALSE. Pointed out by
Johan Billien.
svn path=/trunk/; revision=7725
2008-08-22 Björn Lindqvist <bjourne@gmail.com>
Bug 523939 – Example program for GValue
* gobject/gvalue.c: Add code example that demonstrates GValue's
features.
svn path=/trunk/; revision=7387
2008-08-21 Johan Dahlin <johan@gnome.org>
* gobject.h:
Mark g_object_get_type function as const, it's
a fundamental type and can safely marked as const,
as opposed to traditionally *_get_type functions.
svn path=/trunk/; revision=7378
2008-08-20 Johan Dahlin <johan@gnome.org>
Bug 548689 – The type name for GParamSpec is wrong
* gparam.c (g_param_type_init):
Register the type name as GParam instead of GParamSpec.
svn path=/trunk/; revision=7374
2008-07-27 Tor Lillqvist <tml@novell.com>
* gtype.h
* gtype.c: Revert my change from 2008-07-24. No G_TYPE_FORMAT is
needed. Just use G_GSIZE_FORMAT always when printing GType values.
svn path=/trunk/; revision=7256
2008-07-27 Tor Lillqvist <tml@novell.com>
* configure.in: Set LIB_EXE_MACHINE_FLAG to either X86 or X64 on
Windows. AC_SUBST it.
* */Makefile.am: Correspondingly, pass appropriate -machine
flag to lib.exe when producing the import library for the MS
toolchain.
svn path=/trunk/; revision=7255
2008-07-24 Tor Lillqvist <tml@novell.com>
* gtype.h: Define G_TYPE_FORMAT as the printf format for a GType
value. Either G_GSIZE_FORMAT or "lu".
* gtype.c: Use it instead of the C99 zu.
svn path=/trunk/; revision=7250
2008-07-21 Michael Natterer <mitch@imendio.com>
Reviewed by Tim Janik:
* gsignal.c (g_signal_chain_from_overridden_handler): allocate
the temp GValue array with GSLice.
(g_signal_emit_valist): dito. Remove optimization/obfuscation of
allocating up to 16 GValues on the stack and always use GSLice.
svn path=/trunk/; revision=7229
2008-07-04 Michael Natterer <mitch@imendio.com>
Bug 541208 – Functions to easily install and use signals without
class struct slot
* gobject.symbols
* gsignal.[ch] (g_signal_new_class_handler): the same as
_gtk_binding_signal_new(), to install signals with a callback
instead of a class struct slot as class closure.
The next two functions are C convenience and much easier to use
than the generic overriding and chaining APIs which are intended
primarily for language bindings:
(g_signal_override_class_handler): to override a signal with a
callback instead of a class struct slot.
(g_signal_chain_from_overridden_handler): to chain up from a
signal without class struct slot. The API is similar to
g_signal_emit().
svn path=/trunk/; revision=7157
2008-06-29 Björn Lindqvist <bjourne@gmail.com>
Bug 539626 – Update docstrings for g_object_freeze_notify and
g_object_thaw_notify
* gobject/gobject.c: Explain how the freeze count works.
svn path=/trunk/; revision=7102
2008-06-27 Hans Breuer <hans@breuer.org>
* glib-genmarshal.c : move G_OS_WIN32 inclusion of <io.h> down to
where G_OS_WIN32 will be defined (#540047, Kazuki IWAMOTO)
svn path=/trunk/; revision=7100
2008-06-23 Kristian Rietveld <kris@imendio.com>
* gobject/glib-mkenums.in: introduce an ENUMPREFIX substitution.
* gio/gioenumtypes.h.template: use @ENUMPREFIX@ instead of
hard coding "G" as prefix.
svn path=/trunk/; revision=7096
2008-06-22 Michael Natterer <mitch@imendio.com>
* *.c: remove trailing whitespace from newly added gtk-doc
comments and reformatted some where they contained overly long or
ill-formatted lines.
svn path=/trunk/; revision=7090
2008-06-22 Michael Natterer <mitch@imendio.com>
* *.c: moved includes back to the top of the files (before gtk-doc
SECTION comments). Add "config.h" in all files and move system
included before glib includes. Remove trailing whitespace from
SECTION comments and did some reformatting where lines were overly
long, no documentation content was changed.
svn path=/trunk/; revision=7089
* docs/reference/gobject/tmpl/gobject-unused.sgml:
* gobject/gobject.h:
* gobject/gtype.c:
* gobject/gtype.h:
Move some content for gobject-unused.sgml and cleared empty entries.
The remaining 4 ones should be checked by some else. If they are not
needed. The file can be removed.
svn path=/trunk/; revision=7087
* gobject/gboxed.c:
* gobject/gclosure.c:
* gobject/genums.c:
* gobject/gvalue.c:
Use file-names from the section file for SECTION: comments.
svn path=/trunk/; revision=7072
2008-06-10 13:34:01 Tim Janik <timj@imendio.com>
* tests/threadtests.c: added race condition tester from Michael Meeks
with a couple fixes so it's not triggering development warnings. From:
Bug 537555 - GObject instantiation not thread safe ...
svn path=/trunk/; revision=6983
2008-06-10 13:15:29 Tim Janik <timj@imendio.com>
* gtype.c (g_type_class_ref): fixed race condition where references to
partially initialized classes could be handed out.
svn path=/trunk/; revision=6982
2008-05-28 Michael Natterer <mitch@imendio.com>
* Makefile.am: don't define G_DISABLE_SINGLE_INCLUDES, it's in
the global CPPFLAGS now.
svn path=/trunk/; revision=6952
2008-05-05 Michael Natterer <mitch@imendio.com>
* Makefile.am. build with G_DISABLE_SINGLE_INCLUDES to prevent
code from being checked in that breaks the build of applications
which use G_DISABLE_SINGLE_INCLUDES.
svn path=/trunk/; revision=6876
2008-04-21 Tor Lillqvist <tml@novell.com>
* configure.in
* */Makefile.am: More work on enabling static building on
Windows. When building statically: Also define
GOBJECT_STATIC_COMPILATION in glibconfig.h so that also the
variables in gparamspecs.h get declared without any
dllimport/dllexport decorations. Don't install .def files which
obviously have no meaning for static libraries. Don't create MS
import libraries. Don't do any resource object files.
svn path=/trunk/; revision=6866
2008-03-16 Tor Lillqvist <tml@novell.com>
* configure.in: Don't bother defining Autoconf variables for
glib.def, gmodule.def, gobject.def and gthread.def when this can
be handled easily in */Makefile.am which are the only files that
use them. Remove also TESTGMODULE_EXP which isn't used at all.
* */Makefile.am: Corrsponding changes.
svn path=/trunk/; revision=6722
* gparamspecs.c: (param_gtype_set_default), (param_gtype_validate):
make GParamGType require the set type during construction instead of
using G_TYPE_NONE, which causes issues when setting.
Bug 513073 - g_param_spec_gtype breaks with G_PARAM_CONSTRUCT
svn path=/trunk/; revision=6457
2008-02-05 18:52:07 Tim Janik <timj@imendio.com>
* gtype.c: added recursive mutex to protect class initialization,
default interface initialization and per-class interface construction.
a lock to this recursive mutex is held during user callback invocations
such as initializers or finalizers, effectively allowing only one thread
to run class/interface initializers/finalizers at a time.
also made misc fixups. this fixes:
Bug 64764 - Class initialization isn't thread safe.
svn path=/trunk/; revision=6454
2008-02-05 18:41:22 Tim Janik <timj@imendio.com>
* Makefile.am: integrate tests/.
* tests/: new directory for libgobject tests.
* tests/Makefile.am: build and run threadtests.
* tests/threadtests.c: test multi-threaded initializers for
object classes and interfaces.
svn path=/trunk/; revision=6452
* gobject/glib-genmarshal.c: Add global exit_status variable, and use
it in pad() and process_signature() to return with non-zero error code
when printing warnings. (#495294)
svn path=/trunk/; revision=6098
2007-11-21 21:06:47 Tim Janik <timj@imendio.com>
* Makefile.decl: initialize automake variables EXTRA_DIST and
TEST_PROGS for unconditional appending via += in other makefiles.
define recursive test targets: test, test-report, perf-report,
full-report, as described here:
http://mail.gnome.org/archives/gtk-devel-list/2007-November/msg00000.html
* Makefile.am:
* build/win32/vs8/Makefile.am, build/win32/dirent/Makefile.am:
* build/win32/Makefile.am, build/Makefile.am:
* docs/Makefile.am, docs/reference/Makefile.am:
* docs/reference/glib/Makefile.am, docs/reference/gobject/Makefile.am:
* gmodule/Makefile.am, tests/Makefile.am:
* tests/refcount/Makefile.am, tests/gobject/Makefile.am:
* glib/update-pcre/Makefile.am, glib/libcharset/Makefile.am:
* glib/tests/Makefile.am, glib/pcre/Makefile.am:
* glib/gnulib/Makefile.am, gobject/Makefile.am, m4macros/Makefile.am:
* gthread/Makefile.am, glib/Makefile.am:
include $(top_srcdir)/Makefile.decl, adapted EXTRA_DIST assignments.
* glib/tests/Makefile.am: removed example testing rules.
* glib/tests/testing.c: conditionalized performance and slow tests.
* glib/gtestutils.h:
* glib/gtestutils.c: work around g_test_config_vars not changing its
exported value after value assignments, aparently due to symbol aliases.
* glib/gtester.c: fixed off-by-one error which produced junk in logs.
* configure.in: check for python >= 2.4 and provide $PYTHON for scripts.
svn path=/trunk/; revision=5914
2007-10-13 Sven Herzberg <herzi@gnome-de.org>
Reviewed by Tim Janik.
Created marshallers that don't throw gcc warnings when compiling with
-WUnused (fixes#359165).
* gobject/glib-genmarshal.c: decorate return_value and invocation_hint
with G_GNUC_UNUSED
svn path=/trunk/; revision=5781
2007-09-20 Carlos Garnacho <carlos@imendio.com>
* gtypemodule.h: make sure we define GType g_define_type_id in
G_G_DEFINE_DYNAMIC_TYPE_EXTENDED so it works together with
G_IMPLEMENT_INTERFACE. (#478459)
svn path=/trunk/; revision=5777
2007-08-14 Cody Russell <bratsche@gnome.org>
* gobject/gsignal.c: g_type_default_interface_ref() was not
ensuring working g_signal_list_ids. Added checks for
!G_TYPE_IS_INTERFACE (itype).
(#465625, by some guy who calls himself Yeti)
svn path=/trunk/; revision=5704
Fri Jun 22 11:31:27 2007 Tim Janik <timj@gtk.org>
* gtype.h: reintroduce typedef gulong GType; for C++, to avoid
C++ specific ABI breakage.
svn path=/trunk/; revision=5582
Thu Jun 14 23:32:00 2007 Tim Janik <timj@gtk.org>
* gtype.h: always define GType unconditionally in terms of gsize,
there's no need to jump through a glong hoop ever and this fixes
the printf modifier to %zu.
svn path=/trunk/; revision=5560
Thu Jun 14 22:33:11 2007 Tim Janik <timj@imendio.com>
* gparamspecs.c (g_param_spec_types_init): work around SGI IDO cc,
fixes#363986.
svn path=/trunk/; revision=5559
2007-05-17 Matthias Clasen <mclasen@redhat.com>
* configure.in: Move the compiler-dependency in the G_GNUC_INTERNAL
definition from configure-time to runtime (of the compiler).
(#438869, Damien Carbery)
* glib/gdebug.h:
* glib/gmessages.h:
* glib/gunicodeprivate.h:
* glib/gthreadprivate.h: Move G_GNUC_INTERNAL before function
declarations to fix compilation with sun studio. (#438873,
Damien Carbery)
svn path=/trunk/; revision=5497
2007-04-25 Michael Natterer <mitch@imendio.com>
* gparamspecs.c (param_string_validate): also clear the
NOCOPY_CONTENTS flag when replacing NULL with the empty string.
svn path=/trunk/; revision=5458
2007-04-24 Michael Natterer <mitch@imendio.com>
* gobject/gparamspecs.c (param_string_validate): don't free or
modify static strings, dup them when needed and clear the
G_VALUE_NOCOPY_CONTENTS flag. Fixes bug #432895.
* tests/gobject/paramspec-test.c: test all GParamSpecString
validations with static and allocated strings.
svn path=/trunk/; revision=5454
Tue Apr 3 12:34:14 2007 Tim Janik <timj@gtk.org>
* gobject.[hc]: invoke GObjectClass.constructed() only for newly
constructed objects, and invoke it while the notify queue is
still being frozen, after all CONSTRUCT* properties have been
set and before random other properties are being set.
* applied modified patch from Ryan Lortie to implement
GObjectClass.constructed() to fix#425324.
2007-04-02 Ryan Lortie <desrt@desrt.ca>
* gobject/gobject.h: Add 'constructed' vcall to GObjectClass.
* gobject/gobject.c (g_object_newv): call ->constructed() as last
step of object construction.
svn path=/trunk/; revision=5441
Mon Mar 12 13:30:20 2007 Tim Janik <timj@gtk.org>
* gtype.h: marked purely functional g_type accessors as PURE or CONST,
closes#305100.
svn path=/trunk/; revision=5400
2007-01-02 Tor Lillqvist <tml@novell.com>
* glib-genmarshal.c (main): Add comment about dup(0) and
lack of /dev/stdin on Win32. (#407431)
svn path=/trunk/; revision=5335
2007-01-02 Tor Lillqvist <tml@novell.com>
* glib-genmarshal.c (main): Handle "/dev/stdin" by dup()ing fd 0
so that it works on Win32, too.
svn path=/trunk/; revision=5185
Tue Oct 10 12:06:08 2006 Tim Janik <timj@gtk.org>
* glib-mkenums.in:
* glib-mkenums.1: applied patch from David Necas which introduces
an underscore_name option and fixes#358734.
2006-10-02 Behdad Esfahbod <behdad@gnome.org>
* glib/Makefile.am:
* gobject/Makefile.am:
Include pltcheck.sh in EXTRA_DIST, and remove redefinition of TESTS.
(#358966)
Mon Oct 2 15:50:16 2006 Tim Janik <timj@gtk.org>
* gvalue.c (g_value_peek_pointer): reverted a change to have an
assert instead of a g_return_val_if_fail() here. libraries (and
programs) should only ever g_assert or g_error if there is no way
to carry on with the current program state. that's clearly not
the case here.
* ChangeLog: added missing changelog entry for 2003-12-30.
2006-09-17 Hans Breuer <hans@breuer.org>
* glib/makefile.msc.in gobject/makefile.msc.in : better filtering
of G_GNUC_* stuff when generating .def files. Now also works with
newer (less tolerant) linkers, e.g. from vc2500e
Tue Aug 29 13:27:33 2006 Tim Janik <timj@gtk.org>
* glib-mkenums.in: fixed to print usage and version info on STDOUT
(#322502).
* gobject.c (g_initially_unowned_init): restore ; after G_DEFINE_TYPE.
Wed Aug 23 10:35:32 2006 Tim Janik <timj@gtk.org>
* gobject.[hc]: changed return value of g_value_dup_object(), fixes#343292.
2006-08-23 Sven Neumann <sven@gimp.org>
* gobject/glib-genmarshal.[c1]: added new command-line option
"--internal" that can be used to let glib-genmarshal generate
internal functions using the G_GNUC_INTERNAL attribute (bug #346647).
2006-08-23 Sven Neumann <sven@gimp.org>
* gobject/glib-genmarshal.[c1]: added new command-line option
"--internal" that can be used to let glib-genmarshal generate
internal functions using the G_GNUC_INTERNAL attribute (bug
#346647).
Wed Aug 16 13:55:08 2006 Tim Janik <timj@imendio.com>
* gobject.c: conditionally thaw the notify queue after construction,
so we don't trigger warnings when trying to thaw an unfrozen singleton.
2006-08-05 Matthias Clasen <mclasen@redhat.com>
* gparamspecs.c (g_param_spec_types_init): Don't initialize
struct members with function calls. (#349952)
2006-07-21 Matthias Clasen <mclasen@redhat.com>
* gtypemodule.c (g_type_module_register_type): Copy the complete
value table, not just the first 4 bytes. (#348136, Coverity)
2006-06-14 Matthias Clasen <mclasen@redhat.com>
* glib/gkeyfile.c (g_key_file_to_data): Separate groups by
an empty line (#344868, Christian Persch)
2006-06-14 Tor Lillqvist <tml@novell.com>
2006-06-02 Behdad Esfahbod <behdad@gnome.org>
* gobject/genum.h: Make value_name and value_nick const in structs
_GEnumValue and _GFlagValue. (#317793)
Tue May 2 14:51:03 2006 Tim Janik <timj@gtk.org>
* gtype.h: split up G_DEFINE_*TYPE macro definitions so C CODE arguments
are not passed on to nested macro calls. patch mostly courtesy of Behdad
Esfahbod, fixes#337128.
Tue Mar 7 17:09:07 2006 Tim Janik <timj@gtk.org>
* gobject.c (g_object_compat_control): added case3 to hand out the
original floating flag handler. required by gtk+ >= 2.10.
2006-01-18 Matthias Clasen <mclasen@redhat.com>
* gobject.h: Make g_object_compat_control() visible
for GTK+ compilation, to avoid segfaults on 64bit
platforms.
2005-12-30 Matthias Clasen <mclasen@redhat.com>
* gsignal.c: Remove the handler trash stack, which
is now unused.
(g_signal_init): Remove the restriction that HandlerMatch
must be the same size as GList, and obsolete comments
referring to mem chunks.
Thu Dec 22 14:59:24 2005 Tim Janik <timj@imendio.com>
* gvaluetypes.[hc]: implemented G_TYPE_GTPYE. applied patch
from matthias which implements GType accessors for GValue.
* gparamspecs.[hc]: applied patch from matthias which
implements G_TYPE_PARAM_GTYPE.
* gobject.[hc]:
GUnowned: introduced a new object type that has an initially
floating reference.
g_object_compat_control(): allow setting of a floating flag handler.
