Atomic APIs provide a way to exchange values only if we compare a value
that is equal to the old value, but not to just exchange the value
returning the old one.
However, compilers provide such built-in functions, so we can use them
to expose such functionality to GLib.
The only drawback is that when using an old version of gcc not providing
atomic APIs to swap values, we need to re-implement it with an
implementation that may not be fully atomic, but that is safe enough.
However this codepath should really not be used currently as gcc
introduced __atomic_exchange_n() at version 4.7.4, so 8 years ago.
GArray supports a "zero_terminated" flag, but GPtrArray doesn't.
This is odd, because especially for a pointer array it makes sense
to have a %NULL sentinel. This would be for example useful to track
or construct a strv array with a GPtrArray.
As workaround for this missing feature you could use a GArray instead
(ugly) or to explicitly add the %NULL element. However the latter increases
the "len" of the array, which can be problematic if you want to still use
the GPtrArray for other purposes.
Add API for marking a GPtrArray as %NULL terminated. In that case, the
API will ensure that there is always a valid %NULL sentinel after the
array. Note that the API does not enforce that a %NULL terminated API
actually has any data allocated. That means, even with a %NULL terminated
array, pdata can still be %NULL (only if len is zero).
Add g_ptr_array_new_null_terminated() constructor. The null-terminated flag
cannot be cleared. Once the GPtrArray is flagged to be %NULL terminated, it
sticks. The purpose is that once a user checks whether a GPtrArray instance
is safe to be treated as a %NULL terminated array, the decision does
not need to be re-evaluated.
Also add a g_ptr_array_is_null_terminated(). That is useful because it
allows you to check whether a GPtrArray created by somebody else is safe
to use as a %NULL terminated array. Since there is no API to make an
array not %NULL terminated anymore, this is not error prone.
The new flag is tracked as a guint8 in GRealPtrArray. On common 64 bit
architectures this does not increase the size of the struct as it fits
in an existing hole. Note that this is not a bitfield because it's
probably more efficient to access the entire guint8. However, there is
still a 3 bytes hole (on common 32 and 64 architectures), so if we need
to add more flags in the future, we still have space for 24 bits,
despite the new flag not being a bitfield.
The biggest downside of the patch is the runtime overhead that most
operations now need to check whether %NULL termination is requested.
Includes some tweaks and additional tests by Philip Withnall.
https://gitlab.gnome.org/GNOME/glib/-/issues/353
Many idle and timeout sources are installed as "one shot": called once
and immediately removed. While it's easy to write a simple callback that
returns G_SOURCE_REMOVE, it would also be useful to have some sort of
"visual" marker when reading the code; a way to immediately see that a
callback (which may be defined elsewhere in the code) is meant to be
invoked just once.
Includes additional unit tests by Philip Withnall.
This is more efficient than calling
g_datalist_id_remove() multiple times
in a row, since it only takes the locks
once.
Allow up to 16 keys to be removed in one go.
That is enough for the use we have in GObject,
and it avoids any danger of blowing the stack.
When working with storage (especially GInputStream or GOutputStream) it
is preferred to use page-aligned buffers so that the operating system
can do page-mapping tricks as the operation passes through the kernel.
Another use case is allocating memory used for vectorised operations,
which must be aligned to specific boundaries.
POSIX and Windows, as well as the C11 specification, provide this kind
of allocator functions, and GLib already makes use of it inside GSlice.
It would be convenient to have a public, portable wrapper that other
projects can use.
Fixes: #2574
This is an API analogue of the G_MESSAGES_DEBUG environment variable. It
is intended to be exposed outside applications (for example, as a D-Bus
interface — see follow-up commits) so that there is a uniform interface
for controlling the debug output of an application.
Helps: #1190
This function creates a new hash table, but inherits the functions used
for the hash, comparison, and key/value memory management functions from
another hash table.
The primary use case is to implement a behaviour where you maintain a
hash table by regenerating it, letting the values not migrated be freed.
See the following pseudo code:
```
GHashTable *ht;
init(GList *resources) {
ht = g_hash_table_new (g_str_hash, g_str_equal, g_free, g_free);
for (r in resources)
g_hash_table_insert (ht, strdup (resource_get_key (r)), create_value (r));
}
update(GList *resources) {
GHashTable *new_ht = g_hash_table_new_similar (ht);
for (r in resources) {
if (g_hash_table_steal_extended (ht, resource_get_key (r), &key, &value))
g_hash_table_insert (new_ht, key, value);
else
g_hash_table_insert (new_ht, strdup (resource_get_key (r)), create_value (r));
}
g_hash_table_unref (ht);
ht = new_ht;
}
```
Added `g_alloca0()` which wraps `g_alloca()` and initializes
allocated memory to zeroes.
Added `g_newa0()` which wraps `g_alloca0()` in a typesafe manner.
Refreshed and tweaked by Nishal Kulkarni.
Use g_macro__has_attribute to detect it instead of
hardcoding __GNUC__ || __clang__. This adds support
for a few compiler and is consistent with the rest
of the gmacros.h file.
This allows a pattern like
g_test_message ("cannot reticulate splines: %s", error->message);
g_test_fail ();
to be replaced by the simpler
g_test_fail_printf ("cannot reticulate splines: %s", error->message);
with the secondary benefit of making the message available to TAP
consumers as part of the "not ok" message.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Forming the g_test_skip() message from printf-style arguments seems
common enough to deserve a convenience function.
g_test_incomplete() is mechanically almost equivalent to g_test_skip()
(the semantics are different but the implementation is very similar),
so give it a similar mechanism for symmetry.
Signed-off-by: Simon McVittie <smcv@collabora.com>
g_source_set_name duplicates the string, and this is
showing up as one of the more prominent sources of strdups
in GTK profiles, despite all the names we use being literals.
Add a variant that avoids the overhead.
This should maintain equivalent functionality, apart from that now you
have to pass `--force-fallback-for libpcre` to `meson configure` in
order to use the subproject; rather than specifying
`-Dinternal_pcre=true` to use the internal copy.
This also fixes#642, as the wrapdb copy of libpcre is version 8.37.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
Helps: #962Fixes: #642
On Unix platforms, wait() and friends yield an integer that encodes
how the process exited. Confusingly, this is usually not the same as
the integer passed to exit() or returned from main(): conceptually it's
an integer encoding of this tagged union:
enum { EXITED, SIGNALLED, ... } tag;
union {
int exit_status; /* if EXITED */
struct {
int terminating_signal;
bool core_dumped;
} terminating_signal; /* if SIGNALLED */
...
} detail;
Meanwhile, on Windows, wait statuses and exit statuses are
interchangeable.
I find that it's clearer what is going on if we are consistent about
referring to the result of wait() as a "wait status", and the value
passed to exit() as an "exit status".
GSubprocess already gets this right: g_subprocess_get_status() returns
the wait status, while g_subprocess_get_exit_status() genuinely returns
the exit status. However, the GSpawn family of APIs has tended to
conflate the two.
Confusingly, g_spawn_check_exit_status() has always checked a wait
status, and it would not be correct to pass an exit status to it; so
let's deprecate it in favour of g_spawn_check_wait_status(), which
does the same thing that g_spawn_check_exit_status() always did.
Code that needs backwards-compatibility with older GLib can use:
#if !GLIB_CHECK_VERSION(2, 69, 0)
#define g_spawn_check_wait_status(x) (g_spawn_check_exit_status (x))
#endif
Signed-off-by: Simon McVittie <smcv@collabora.com>
Because sometimes you don't want a lone "%s", and you don't
want the compiler yelling at you about format strings that
don't have any format in them.
Closes#663
It is cleaner to define glib_typeof() in a header included after
gversionmacros.h so we can use GLIB_VERSION_MIN_REQUIRED directly
instead of doing it everywhere glib_typeof() is used.
This allows introspection to properly handle them as GPatternSpec
methods, as per this deprecate g_pattern_match() and
g_pattern_match_string() functions.
Fall back to compiler version checks only when `__has_attribute()` is not
available.
clang-cl doesn't define `__GNU__`, but still accepts attributes. This change
gets rid of a lot of warnings when building GLib with clang-cl. For GCC and
non-cl Clang nothing should change.
This is basically glnx_steal_fd() from libglnx. We already had two
private implementations of it in GLib.
Signed-off-by: Simon McVittie <smcv@collabora.com>
This is a simple wrapper around the new source/target FD mapping
functionality in `fork_exec()`.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
Helps: #2097
This adds g_string_replace(), a function that replaces instances of one string
with another in a GString. It allows the caller to specify the maximum number
of replacements to perform, and returns the number of replacements performed
to the caller.
Fixes: #225
This will replace the existing `g_memdup()` function, which has an
unavoidable security flaw of taking its `byte_size` argument as a
`guint` rather than as a `gsize`. Most callers will expect it to be a
`gsize`, and may pass in large values which could silently be truncated,
resulting in an undersize allocation compared to what the caller
expects.
This could lead to a classic buffer overflow vulnerability for many
callers of `g_memdup()`.
`g_memdup2()`, in comparison, takes its `byte_size` as a `gsize`.
Spotted by Kevin Backhouse of GHSL.
Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
Helps: GHSL-2021-045
Helps: #2319
