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>

12 files changed, 55 insertions, 13 deletions

diff --git a/src/corelib/global/qglobal.h b/src/corelib/global/qglobal.h
index fba8b019e7..391466448f 100644
--- a/src/corelib/global/qglobal.h
+++ b/src/corelib/global/qglobal.h
@@ -58,7 +58,10 @@
 #if !defined(QT_BUILD_QMAKE) && !defined(QT_BUILD_CONFIGURE)
 #include <QtCore/qconfig.h>
 #include <QtCore/qfeatures.h>
+#endif
 #define QT_SUPPORTS(FEATURE) (!defined(QT_NO_##FEATURE))
+#if QT_VERSION >= QT_VERSION_CHECK(6,0,0)
+#  define QT_NO_UNSHARABLE_CONTAINERS
 #endif
 
 /* These two macros makes it possible to turn the builtin line expander into a
diff --git a/src/corelib/tools/qarraydata.cpp b/src/corelib/tools/qarraydata.cpp
index 825b3289c7..12736d5c2e 100644
--- a/src/corelib/tools/qarraydata.cpp
+++ b/src/corelib/tools/qarraydata.cpp
@@ -75,10 +75,13 @@ QArrayData *QArrayData::allocate(size_t objectSize, size_t alignment,
             && !(alignment & (alignment - 1)));
 
     // Don't allocate empty headers
-    if (!(options & RawData) && !capacity)
-        return !(options & Unsharable)
-            ? const_cast<QArrayData *>(&qt_array_empty)
-            : const_cast<QArrayData *>(&qt_array_unsharable_empty);
+    if (!(options & RawData) && !capacity) {
+#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
+        if (options & Unsharable)
+            return const_cast<QArrayData *>(&qt_array_unsharable_empty);
+#endif
+        return const_cast<QArrayData *>(&qt_array_empty);
+    }
 
     size_t headerSize = sizeof(QArrayData);
 
@@ -118,8 +121,10 @@ void QArrayData::deallocate(QArrayData *data, size_t objectSize,
             && !(alignment & (alignment - 1)));
     Q_UNUSED(objectSize) Q_UNUSED(alignment)
 
+#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
     if (data == &qt_array_unsharable_empty)
         return;
+#endif
 
     Q_ASSERT_X(!data->ref.isStatic(), "QArrayData::deallocate", "Static data can not be deleted");
     ::free(data);
diff --git a/src/corelib/tools/qarraydata.h b/src/corelib/tools/qarraydata.h
index ffb2b8765e..10a9e35542 100644
--- a/src/corelib/tools/qarraydata.h
+++ b/src/corelib/tools/qarraydata.h
@@ -80,7 +80,9 @@ struct Q_CORE_EXPORT QArrayData
 
     enum AllocationOption {
         CapacityReserved    = 0x1,
+#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
         Unsharable          = 0x2,
+#endif
         RawData             = 0x4,
         Grow                = 0x8,
 
@@ -99,8 +101,10 @@ struct Q_CORE_EXPORT QArrayData
     AllocationOptions detachFlags() const
     {
         AllocationOptions result;
+#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
         if (!ref.isSharable())
             result |= Unsharable;
+#endif
         if (capacityReserved)
             result |= CapacityReserved;
         return result;
diff --git a/src/corelib/tools/qarraydatapointer.h b/src/corelib/tools/qarraydatapointer.h
index 533f7a306f..2245106ec0 100644
--- a/src/corelib/tools/qarraydatapointer.h
+++ b/src/corelib/tools/qarraydatapointer.h
@@ -134,6 +134,7 @@ public:
         return (!d->isMutable() || d->ref.isShared());
     }
 
+#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
     void setSharable(bool sharable)
     {
         if (needsDetach()) {
@@ -147,6 +148,9 @@ public:
         }
     }
 
+    bool isSharable() const { return d->isSharable(); }
+#endif
+
     void swap(QArrayDataPointer &other)
     {
         qSwap(d, other.d);
diff --git a/src/corelib/tools/qcontiguouscache.h b/src/corelib/tools/qcontiguouscache.h
index d601ddb819..e05ef33aa2 100644
--- a/src/corelib/tools/qcontiguouscache.h
+++ b/src/corelib/tools/qcontiguouscache.h
@@ -104,7 +104,9 @@ public:
 
     inline void detach() { if (d->ref.load() != 1) detach_helper(); }
     inline bool isDetached() const { return d->ref.load() == 1; }
+#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
     inline void setSharable(bool sharable) { if (!sharable) detach(); d->sharable = sharable; }
+#endif
 
     QContiguousCache<T> &operator=(const QContiguousCache<T> &other);
 #ifdef Q_COMPILER_RVALUE_REFS
diff --git a/src/corelib/tools/qhash.h b/src/corelib/tools/qhash.h
index 40e501355c..f68b02be2c 100644
--- a/src/corelib/tools/qhash.h
+++ b/src/corelib/tools/qhash.h
@@ -330,7 +330,9 @@ public:
 
     inline void detach() { if (d->ref.isShared()) detach_helper(); }
     inline bool isDetached() const { return !d->ref.isShared(); }
+#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
     inline void setSharable(bool sharable) { if (!sharable) detach(); if (d != &QHashData::shared_null) d->sharable = sharable; }
+#endif
     inline bool isSharedWith(const QHash<Key, T> &other) const { return d == other.d; }
 
     void clear();
diff --git a/src/corelib/tools/qlinkedlist.h b/src/corelib/tools/qlinkedlist.h
index bdacdbcd26..3377d1bbc3 100644
--- a/src/corelib/tools/qlinkedlist.h
+++ b/src/corelib/tools/qlinkedlist.h
@@ -106,7 +106,9 @@ public:
     inline void detach()
     { if (d->ref.isShared()) detach_helper2(this->e); }
     inline bool isDetached() const { return !d->ref.isShared(); }
+#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
     inline void setSharable(bool sharable) { if (!sharable) detach(); if (d != &QLinkedListData::shared_null) d->sharable = sharable; }
+#endif
     inline bool isSharedWith(const QLinkedList<T> &other) const { return d == other.d; }
 
     inline bool isEmpty() const { return d->size == 0; }
diff --git a/src/corelib/tools/qlist.h b/src/corelib/tools/qlist.h
index 3a0d01aa8d..9e4ba70908 100644
--- a/src/corelib/tools/qlist.h
+++ b/src/corelib/tools/qlist.h
@@ -146,6 +146,7 @@ public:
     }
 
     inline bool isDetached() const { return !d->ref.isShared(); }
+#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
     inline void setSharable(bool sharable)
     {
         if (sharable == d->ref.isSharable())
@@ -155,6 +156,7 @@ public:
         if (d != &QListData::shared_null)
             d->ref.setSharable(sharable);
     }
+#endif
     inline bool isSharedWith(const QList<T> &other) const { return d == other.d; }
 
     inline bool isEmpty() const { return p.isEmpty(); }
diff --git a/src/corelib/tools/qmap.h b/src/corelib/tools/qmap.h
index 487039ccfb..76f8bd6f17 100644
--- a/src/corelib/tools/qmap.h
+++ b/src/corelib/tools/qmap.h
@@ -377,6 +377,7 @@ public:
 
     inline void detach() { if (d->ref.isShared()) detach_helper(); }
     inline bool isDetached() const { return !d->ref.isShared(); }
+#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
     inline void setSharable(bool sharable)
     {
         if (sharable == d->ref.isSharable())
@@ -386,6 +387,7 @@ public:
         // Don't call on shared_null
         d->ref.setSharable(sharable);
     }
+#endif
     inline bool isSharedWith(const QMap<Key, T> &other) const { return d == other.d; }
 
     void clear();
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
     {
diff --git a/src/corelib/tools/qset.h b/src/corelib/tools/qset.h
index ad2f91b983..0cc704b6cf 100644
--- a/src/corelib/tools/qset.h
+++ b/src/corelib/tools/qset.h
@@ -91,7 +91,9 @@ public:
 
     inline void detach() { q_hash.detach(); }
     inline bool isDetached() const { return q_hash.isDetached(); }
+#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
     inline void setSharable(bool sharable) { q_hash.setSharable(sharable); }
+#endif
 
     inline void clear() { q_hash.clear(); }
 
diff --git a/src/corelib/tools/qvector.h b/src/corelib/tools/qvector.h
index b0be98c296..6f7c534085 100644
--- a/src/corelib/tools/qvector.h
+++ b/src/corelib/tools/qvector.h
@@ -107,6 +107,7 @@ public:
 
     inline void detach();
     inline bool isDetached() const { return !d->ref.isShared(); }
+#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
     inline void setSharable(bool sharable)
     {
         if (sharable == d->ref.isSharable())
@@ -122,6 +123,7 @@ public:
         }
         Q_ASSERT(d->ref.isSharable() == sharable);
     }
+#endif
 
     inline bool isSharedWith(const QVector<T> &other) const { return d == other.d; }
 
@@ -329,10 +331,12 @@ template <typename T>
 void QVector<T>::detach()
 {
     if (!isDetached()) {
-        if (d->alloc)
-            reallocData(d->size, int(d->alloc));
-        else
+#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
+        if (!d->alloc)
             d = Data::unsharableEmpty();
+        else
+#endif
+            reallocData(d->size, int(d->alloc));
     }
     Q_ASSERT(isDetached());
 }
@@ -484,7 +488,9 @@ void QVector<T>::reallocData(const int asize, const int aalloc, QArrayData::Allo
                 x = Data::allocate(aalloc, options);
                 Q_CHECK_PTR(x);
                 // aalloc is bigger then 0 so it is not [un]sharedEmpty
+#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
                 Q_ASSERT(x->ref.isSharable() || options.testFlag(QArrayData::Unsharable));
+#endif
                 Q_ASSERT(!x->ref.isStatic());
                 x->size = asize;
 
@@ -550,7 +556,9 @@ void QVector<T>::reallocData(const int asize, const int aalloc, QArrayData::Allo
 
     Q_ASSERT(d->data());
     Q_ASSERT(uint(d->size) <= d->alloc);
+#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
     Q_ASSERT(d != Data::unsharableEmpty());
+#endif
     Q_ASSERT(aalloc ? d != Data::sharedNull() : d == Data::sharedNull());
     Q_ASSERT(d->alloc >= uint(aalloc));
     Q_ASSERT(d->size == asize);