The last part of the reference counting saga.
Now that we have:
- reference counter types
- reference counted allocations
we can finally add reference counted strings using reference counted
allocations to avoid creating a new String type, and reimplementing
every single string-based API.
GArcBox is the atomic reference counting version of GRcBox. Unlike
GRcBox, the reference acquisition and release on GArcBox are guaranteed
to be atomic, and thus they can be performed from different threads.
This is similar to Rust's Arc<Box<T>> combination of traits.
It is useful to provide a "reference counted allocation" API that can
add reference counting semantics to any memory allocation. This allows
turning data structures that usually are placed on the stack into memory
that can be placed on the heap without:
- adding a public reference count field
- implementing copy/free semantics
This mechanism is similar to Rust's Rc<Box<T>> combination of traits,
and uses a Valgrind-friendly overallocation mechanism to store the
reference count into a private data segment, like we do with GObject's
private instance data.
We have a common pattern for reference counting in GLib, but we always
implement it with ad hoc code. This is a good chance at trying to
standardise the implementation and make it public, so that other code
using GLib can take advantage of shared behaviour and semantics.
Instead of simply taking an integer variable, we should create type
aliases, to immediately distinguish the reference counting semantics of
the code; we can handle mixing atomic reference counting with a
non-atomic type (and vice versa) by using differently signed values for
the atomic and non-atomic cases.
The gatomicrefcount type is modelled on the Linux kernel refcount_t
type; the grefcount type is added to let single-threaded code bases to
avoid paying the price of atomic memory barriers on reference counting
operations.
Many UUID users will just need a random string, which can be generated
simply by calling the function g_uuid_string_random().
Based on original patch by
Marc-André Lureau <marcandre.lureau@gmail.com>
https://bugzilla.gnome.org/show_bug.cgi?id=639078
Add some helpers for builds-checked unsigned integer arithmetic to GLib.
These will be based on compiler intrinsics where they are available,
falling back to standard manual checks otherwise.
The fallback case needs to be implemented as a function (which we do
inline) because we cannot rely on statement expressions. We also
implement the intrinsics case as an inline in order to avoid people
accidentally writing non-portable code which depends on static
evaluation of the builtin.
For now there is only support for addition and multiplication for guint,
guint64 and gsize. It may make sense to add support for subtraction or
for the signed equivalents of those types in the future if we find a use
for that.
https://bugzilla.gnome.org/show_bug.cgi?id=503096
