Get rid of QArrayData::sharedNull()

Remove the last places where those got used and avoid
allocations when we resize to 0.

Change-Id: Ib553f4e7ce7cc24c31da15a55a86d18bdf1cc5c3
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

4 files changed, 6 insertions, 44 deletions

diff --git a/src/corelib/text/qbytearray.cpp b/src/corelib/text/qbytearray.cpp
index 350fa3be25..e0f720bc86 100644
--- a/src/corelib/text/qbytearray.cpp
+++ b/src/corelib/text/qbytearray.cpp
@@ -1732,7 +1732,7 @@ QByteArray QByteArray::nulTerminated() const
 
 QByteArray &QByteArray::prepend(const QByteArray &ba)
 {
-    if (size() == 0 && d->isStatic() && ba.d.isMutable()) {
+    if (size() == 0 && ba.d.isMutable()) {
         *this = ba;
     } else if (ba.size() != 0) {
         QByteArray tmp = *this;
@@ -1825,7 +1825,7 @@ QByteArray &QByteArray::prepend(char ch)
 
 QByteArray &QByteArray::append(const QByteArray &ba)
 {
-    if (size() == 0 && d->isStatic() && ba.d.isMutable()) {
+    if (size() == 0 && ba.d.isMutable()) {
         *this = ba;
     } else if (ba.size() != 0) {
         if (d->needsDetach() || size() + ba.size() > capacity())
diff --git a/src/corelib/tools/qarraydata.cpp b/src/corelib/tools/qarraydata.cpp
index 42599bbf2a..1a369a879a 100644
--- a/src/corelib/tools/qarraydata.cpp
+++ b/src/corelib/tools/qarraydata.cpp
@@ -147,25 +147,7 @@ qCalculateGrowingBlockSize(size_t elementCount, size_t elementSize, size_t heade
     return result;
 }
 
-// End of qtools_p.h implementation
-
-QT_WARNING_PUSH
-QT_WARNING_DISABLE_GCC("-Wmissing-field-initializers")
-
-const QArrayData QArrayData::shared_null[2] = {
-    { Q_BASIC_ATOMIC_INITIALIZER(-1), 0, 0 }, // shared null
-    /* zero initialized terminator */};
-
-static const QArrayData emptyNotNullShared[2] = {
-    { Q_BASIC_ATOMIC_INITIALIZER(-1), 0, 0 }, // shared empty
-    /* zero initialized terminator */};
-
-QT_WARNING_POP
-
-static const QArrayData &qt_array_empty = emptyNotNullShared[0];
-
-static inline size_t calculateBlockSize(size_t &capacity, size_t objectSize, size_t headerSize,
-                                        uint options)
+static inline size_t calculateBlockSize(size_t &capacity, size_t objectSize, size_t headerSize, uint options)
 {
     // Calculate the byte size
     // allocSize = objectSize * capacity + headerSize, but checked for overflow
@@ -199,9 +181,8 @@ void *QArrayData::allocate(QArrayData **dptr, size_t objectSize, size_t alignmen
             && !(alignment & (alignment - 1)));
 
     if (capacity == 0) {
-        // optimization for empty headers
-        *dptr = const_cast<QArrayData *>(&qt_array_empty);
-        return sharedNullData();
+        *dptr = nullptr;
+        return nullptr;
     }
 
     size_t headerSize = sizeof(QArrayData);
diff --git a/src/corelib/tools/qarraydata.h b/src/corelib/tools/qarraydata.h
index b3b559e222..fe8827afb8 100644
--- a/src/corelib/tools/qarraydata.h
+++ b/src/corelib/tools/qarraydata.h
@@ -77,24 +77,16 @@ struct Q_CORE_EXPORT QArrayData
     /// Returns true if sharing took place
     bool ref()
     {
-        if (!isStatic())
-            ref_.ref();
+        ref_.ref();
         return true;
     }
 
     /// Returns false if deallocation is necessary
     bool deref()
     {
-        if (isStatic())
-            return true;
         return ref_.deref();
     }
 
-    bool isStatic() const
-    {
-        return ref_.loadRelaxed() == -1;
-    }
-
     bool isShared() const
     {
         return ref_.loadRelaxed() != 1;
@@ -133,14 +125,6 @@ struct Q_CORE_EXPORT QArrayData
             size_t objectSize, size_t newCapacity, ArrayOptions newOptions = DefaultAllocationFlags) Q_DECL_NOTHROW;
     static void deallocate(QArrayData *data, size_t objectSize,
             size_t alignment) noexcept;
-
-    static const QArrayData shared_null[2];
-    static QArrayData *sharedNull() noexcept { return const_cast<QArrayData*>(shared_null); }
-    static void *sharedNullData()
-    {
-        QArrayData *const null = const_cast<QArrayData *>(&shared_null[1]);
-        return null;
-    }
 };
 
 Q_DECLARE_OPERATORS_FOR_FLAGS(QArrayData::ArrayOptions)
diff --git a/src/corelib/tools/qarraydatapointer.h b/src/corelib/tools/qarraydatapointer.h
index 8e30373211..1f9a9d840c 100644
--- a/src/corelib/tools/qarraydatapointer.h
+++ b/src/corelib/tools/qarraydatapointer.h
@@ -78,7 +78,6 @@ public:
     explicit QArrayDataPointer(QPair<QTypedArrayData<T> *, T *> adata, size_t n = 0)
         : d(adata.first), ptr(adata.second), size(int(n))
     {
-        Q_CHECK_PTR(d);
     }
 
     static QArrayDataPointer fromRawData(const T *rawData, size_t length)
@@ -183,7 +182,6 @@ public:
     void ref() noexcept { if (d) d->ref(); }
     bool deref() noexcept { return !d || d->deref(); }
     bool isMutable() const noexcept { return d; }
-    bool isStatic() const noexcept { return !d; }
     bool isShared() const noexcept { return !d || d->isShared(); }
     bool isSharedWith(const QArrayDataPointer &other) const noexcept { return d && d == other.d; }
     bool needsDetach() const noexcept { return !d || d->needsDetach(); }
@@ -199,7 +197,6 @@ private:
     Q_REQUIRED_RESULT QPair<Data *, T *> clone(QArrayData::ArrayOptions options) const
     {
         QPair<Data *, T *> pair = Data::allocate(detachCapacity(size), options);
-        Q_CHECK_PTR(pair.first);
         QArrayDataPointer copy(pair.first, pair.second, 0);
         if (size)
             copy->copyAppend(begin(), end());