Deprecate setSharable in Qt containers

The ability to set a container to be unsharable has very little use and
it costs us an extra conditional for every refcount up and possibly
down.

This change is a no-op for current Qt 5. It shuffles a few things around
just so Qt can compile if you define QT_NO_UNSHARABLE_CONTAINERS. That
is done to ease the fixing of the code in Qt 6 and to make my life
easier: I'll keep that defined in my local Qt build so I can catch any
misuses of this deprecated API.

The newly deprecated methods are not marked QT_DEPRECATED because the
bootstrapped tools wouldn't build -- they're built with QT_NO_DEPRECATED
defined, which causes build errors.

[ChangeLog][QtCore] The setSharable() and isSharable() functions in Qt
containers has been deprecated and will be removed in Qt 6. New
applications should not use this feature, while old applications that
may be using this (undocumented) feature should port away from it.

Discussed-on: http://lists.qt-project.org/pipermail/development/2014-February/015724.html
Change-Id: I789771743dcaed6a43eccd99382f8b3ffa61e479
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

1 files changed, 12 insertions, 6 deletions

diff --git a/src/corelib/tools/qrefcount.h b/src/corelib/tools/qrefcount.h
index 84314b1fcc..3a8f0f3982 100644
--- a/src/corelib/tools/qrefcount.h
+++ b/src/corelib/tools/qrefcount.h
@@ -55,8 +55,10 @@ class RefCount
 public:
     inline bool ref() Q_DECL_NOTHROW {
         int count = atomic.load();
+#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
         if (count == 0) // !isSharable
             return false;
+#endif
         if (count != -1) // !isStatic
             atomic.ref();
         return true;
@@ -64,13 +66,16 @@ public:
 
     inline bool deref() Q_DECL_NOTHROW {
         int count = atomic.load();
+#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
         if (count == 0) // !isSharable
             return false;
+#endif
         if (count == -1) // isStatic
             return true;
         return atomic.deref();
     }
 
+#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
     bool setSharable(bool sharable) Q_DECL_NOTHROW
     {
         Q_ASSERT(!isShared());
@@ -80,17 +85,18 @@ public:
             return atomic.testAndSetRelaxed(1, 0);
     }
 
-    bool isStatic() const Q_DECL_NOTHROW
-    {
-        // Persistent object, never deleted
-        return atomic.load() == -1;
-    }
-
     bool isSharable() const Q_DECL_NOTHROW
     {
         // Sharable === Shared ownership.
         return atomic.load() != 0;
     }
+#endif
+
+    bool isStatic() const Q_DECL_NOTHROW
+    {
+        // Persistent object, never deleted
+        return atomic.load() == -1;
+    }
 
     bool isShared() const Q_DECL_NOTHROW
     {