We have to ensure that the memory location is sufficiently aligned to
store any object. This unbreaks the code for CHERI where using gsize
results in values that are only aligned to 8 bytes, but we need 16 byte
alignment for pointers. This is fully API/ABI compatible since amount
of padding before the actual allocation does not change for existing
architectures, only for CHERI.
Helps: https://gitlab.gnome.org/GNOME/glib/-/issues/2842
We can use pointer exchange now to avoid doing two operations to switch
to the new data pointer.
Since we're asserting in case of invalid data, we can just do this check
at later point, without involving any different behavior.
This changes in the unlikely case that G_DISABLE_ASSERT is defined, as in such
case we should undo the operation.
These have all been added manually, as I’ve finished all the files which
I can automatically detect.
All the license headers in this commit are for LGPL-2.1-or-later, and
all have been double-checked against the license paragraph in the file
header.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
Helps: #1415
The problem occurs because we keep a pointer inside the allocated block,
instead of a pointer to the start of the block:
```
==180238== 16 bytes in 1 blocks are possibly lost in loss record 3,086 of 16,075
==180238== at 0x483980B: malloc (vg_replace_malloc.c:309)
==180238== by 0x548942C: g_malloc (gmem.c:102)
==180238== by 0x54A4748: g_slice_alloc (gslice.c:1025)
==180238== by 0x53D0AAF: freelist_alloc (gatomicarray.c:77)
==180238== by 0x53D0B85: _g_atomic_array_copy (gatomicarray.c:133)
==180238== by 0x53F8E6D: iface_node_set_offset_L (gtype.c:1347)
==180238== by 0x53F91F1: type_node_add_iface_entry_W (gtype.c:1444)
==180238== by 0x53F93DF: type_add_interface_Wm (gtype.c:1477)
==180238== by 0x53FC946: g_type_add_interface_static (gtype.c:2852)
==180238== by 0x4A3D53A: gtk_menu_shell_accessible_get_type_once (gtkmenushellaccessible.c:26)
==180238== by 0x4A3D495: gtk_menu_shell_accessible_get_type (gtkmenushellaccessible.c:26)
==180238== by 0x4C8AC44: gtk_menu_shell_class_init (gtkmenushell.c:424)
```
Note we cannot use VALGRIND_FREELIKE_BLOCK() in freelist_free() because we
have not actually freed the FreeListNode and need to dereference it in
freelist_alloc() to decide whether to reuse the block. That would result
in a use-after-free warning before we would get a chance to call
VALGRIND_MALLOCLIKE_BLOCK() in the reuse path.
Also note that this free list only ever grows: it never shrinks for the
lifetime of the application, so nothing here will ever be truely freed,
although unused elements are eligible for reuse.
Fix suggested by Philip Withnall
Related: #2076
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.
