[glib: 3/3] Merge branch 'atomic-exchange-pre-value' into 'main'

[Philip Withnall <pwithnall src gnome org>]

commit e5ccbe09da3c16608d39fac033ce3928caad3269
Merge: 5655af6ada 922bc1d995
Author: Philip Withnall <philip tecnocode co uk>
Date:   Thu Jun 23 13:19:05 2022 +0000

    Merge branch 'atomic-exchange-pre-value' into 'main'
    
    gatomic: Add Compare and Exchange functions that returns the previous value
    
    See merge request GNOME/glib!2766

 docs/reference/glib/glib-sections.txt |   2 +
 glib/gatomic.c                        | 132 ++++++++++++++++++++++++++++++++++
 glib/gatomic.h                        |  62 ++++++++++++++--
 glib/tests/atomic.c                   |  97 ++++++++++++++++++++++++-
 glib/tests/cxx.cpp                    |  40 +++++++++++
 meson.build                           |   2 +-
 6 files changed, 328 insertions(+), 7 deletions(-)
---
diff --cc glib/gatomic.c
index 1ab4fde91c,499fd336f3..6c1ea768e7
--- a/glib/gatomic.c
+++ b/glib/gatomic.c
@@@ -430,9 -463,44 +463,44 @@@ gboolea
                                                  oldval, newval);
  }
  
+  /**
+  * g_atomic_pointer_compare_and_exchange_full:
+  * @atomic: (not nullable): a pointer to a #gpointer-sized value
+  * @oldval: the value to compare with
+  * @newval: the value to conditionally replace with
+  * @preval: (not nullable) (out): the contents of @atomic before this operation
+  *
+  * Compares @atomic to @oldval and, if equal, sets it to @newval.
+  * If @atomic was not equal to @oldval then no change occurs.
+  * In any case the value of @atomic before this operation is stored in @preval.
+  *
+  * This compare and exchange is done atomically.
+  *
+  * Think of this operation as an atomic version of
+  * `{ *preval = *atomic; if (*atomic == oldval) { *atomic = newval; return TRUE; } else return FALSE; }`.
+  *
+  * This call acts as a full compiler and hardware memory barrier.
+  *
+  * See also g_atomic_pointer_compare_and_exchange()
+  *
+  * Returns: %TRUE if the exchange took place
+  *
+  * Since: 2.74
+  **/
+ gboolean
+ (g_atomic_pointer_compare_and_exchange_full) (void     *atomic,
+                                               gpointer  oldval,
+                                               gpointer  newval,
+                                               void     *preval)
+ {
+   return g_atomic_pointer_compare_and_exchange_full ((gpointer *) atomic,
+                                                      oldval, newval,
+                                                      (gpointer *) preval);
+ }
+ 
  /**
   * g_atomic_pointer_exchange:
 - * @atomic: a pointer to a #gint or #guint
 + * @atomic: a pointer to a #gpointer-sized value
   * @newval: the value to replace with
   *
   * Sets the @atomic to @newval and returns the old value from @atomic.