Fix Clang -Wexpansion-to-defined warning by deprecating QT_SUPPORTS

The C and C++ standards say it's undefined whether the preprocessor
supports macros that expand to defined() will operate as an ifdef.
Clang 3.9 started complaining about that fact.

One solution was to change QT_SUPPORTS to check for zero or one, which
means we need to change the #defines QT_NO_xxx to #define QT_NO_xxx 1.
The C standard says we don't need to #define to 0, as an unknown token
is interpreted as zero. However, that might produce a warning (GCC with
-Wundef), so changing the macro this way is not recommended.

Instead, we deprecate the macro and replace the uses with #ifdef/ndef.

Change-Id: Id75834dab9ed466e94c7ffff1444874d5680b96a
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

12 files changed, 22 insertions, 19 deletions

diff --git a/src/corelib/global/qglobal.h b/src/corelib/global/qglobal.h
index 5bb1ce77bd..a7183cb983 100644
--- a/src/corelib/global/qglobal.h
+++ b/src/corelib/global/qglobal.h
@@ -55,6 +55,9 @@
 #include <QtCore/qfeatures.h>
 #endif
 
+// The QT_SUPPORTS macro is deprecated. Don't use it in new code.
+// Instead, use #ifdef/ndef QT_NO_feature.
+// ### Qt6: remove macro
 #ifdef _MSC_VER
 #  define QT_SUPPORTS(FEATURE) (!defined QT_NO_##FEATURE)
 #else
diff --git a/src/corelib/tools/qarraydata.cpp b/src/corelib/tools/qarraydata.cpp
index fa6556f7d9..eb6ce21282 100644
--- a/src/corelib/tools/qarraydata.cpp
+++ b/src/corelib/tools/qarraydata.cpp
@@ -65,7 +65,7 @@ QArrayData *QArrayData::allocate(size_t objectSize, size_t alignment,
 
     // Don't allocate empty headers
     if (!(options & RawData) && !capacity) {
-#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
+#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
         if (options & Unsharable)
             return const_cast<QArrayData *>(&qt_array_unsharable_empty);
 #endif
@@ -110,7 +110,7 @@ QArrayData *QArrayData::allocate(size_t objectSize, size_t alignment,
         quintptr data = (quintptr(header) + sizeof(QArrayData) + alignment - 1)
                 & ~(alignment - 1);
 
-#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
+#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
         header->ref.atomic.store(bool(!(options & Unsharable)));
 #else
         header->ref.atomic.store(1);
@@ -132,7 +132,7 @@ void QArrayData::deallocate(QArrayData *data, size_t objectSize,
             && !(alignment & (alignment - 1)));
     Q_UNUSED(objectSize) Q_UNUSED(alignment)
 
-#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
+#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
     if (data == &qt_array_unsharable_empty)
         return;
 #endif
diff --git a/src/corelib/tools/qarraydata.h b/src/corelib/tools/qarraydata.h
index 865bd4325d..cbbfe1bea2 100644
--- a/src/corelib/tools/qarraydata.h
+++ b/src/corelib/tools/qarraydata.h
@@ -72,7 +72,7 @@ struct Q_CORE_EXPORT QArrayData
 
     enum AllocationOption {
         CapacityReserved    = 0x1,
-#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
+#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
         Unsharable          = 0x2,
 #endif
         RawData             = 0x4,
@@ -249,7 +249,7 @@ struct QTypedArrayData
         return allocate(/* capacity */ 0);
     }
 
-#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
+#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
     static QTypedArrayData *unsharableEmpty()
     {
         Q_STATIC_ASSERT(sizeof(QTypedArrayData) == sizeof(QArrayData));
diff --git a/src/corelib/tools/qarraydatapointer.h b/src/corelib/tools/qarraydatapointer.h
index 9804d2c2d5..615d7c5f80 100644
--- a/src/corelib/tools/qarraydatapointer.h
+++ b/src/corelib/tools/qarraydatapointer.h
@@ -127,7 +127,7 @@ public:
         return (!d->isMutable() || d->ref.isShared());
     }
 
-#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
+#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
     void setSharable(bool sharable)
     {
         if (needsDetach()) {
diff --git a/src/corelib/tools/qcontiguouscache.h b/src/corelib/tools/qcontiguouscache.h
index 41d198f9bc..d546e949c2 100644
--- a/src/corelib/tools/qcontiguouscache.h
+++ b/src/corelib/tools/qcontiguouscache.h
@@ -96,7 +96,7 @@ 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)
+#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
     inline void setSharable(bool sharable) { if (!sharable) detach(); d->sharable = sharable; }
 #endif
 
diff --git a/src/corelib/tools/qhash.h b/src/corelib/tools/qhash.h
index a18dd74706..a5bde40fb8 100644
--- a/src/corelib/tools/qhash.h
+++ b/src/corelib/tools/qhash.h
@@ -266,7 +266,7 @@ public:
 
     inline void detach() { if (d->ref.isShared()) detach_helper(); }
     inline bool isDetached() const { return !d->ref.isShared(); }
-#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
+#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
     inline void setSharable(bool sharable) { if (!sharable) detach(); if (d != &QHashData::shared_null) d->sharable = sharable; }
 #endif
     bool isSharedWith(const QHash &other) const { return d == other.d; }
diff --git a/src/corelib/tools/qlinkedlist.h b/src/corelib/tools/qlinkedlist.h
index 110529d843..710bf5a9f2 100644
--- a/src/corelib/tools/qlinkedlist.h
+++ b/src/corelib/tools/qlinkedlist.h
@@ -99,7 +99,7 @@ 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)
+#if !defined(QT_NO_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; }
diff --git a/src/corelib/tools/qlist.h b/src/corelib/tools/qlist.h
index e04a6be1ab..381875e96f 100644
--- a/src/corelib/tools/qlist.h
+++ b/src/corelib/tools/qlist.h
@@ -169,7 +169,7 @@ public:
     }
 
     inline bool isDetached() const { return !d->ref.isShared(); }
-#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
+#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
     inline void setSharable(bool sharable)
     {
         if (sharable == d->ref.isSharable())
diff --git a/src/corelib/tools/qmap.h b/src/corelib/tools/qmap.h
index ed49e70f4e..7b5a643a1e 100644
--- a/src/corelib/tools/qmap.h
+++ b/src/corelib/tools/qmap.h
@@ -359,7 +359,7 @@ public:
 
     inline void detach() { if (d->ref.isShared()) detach_helper(); }
     inline bool isDetached() const { return !d->ref.isShared(); }
-#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
+#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
     inline void setSharable(bool sharable)
     {
         if (sharable == d->ref.isSharable())
diff --git a/src/corelib/tools/qrefcount.h b/src/corelib/tools/qrefcount.h
index a390989e76..bff6885d65 100644
--- a/src/corelib/tools/qrefcount.h
+++ b/src/corelib/tools/qrefcount.h
@@ -47,7 +47,7 @@ class RefCount
 public:
     inline bool ref() Q_DECL_NOTHROW {
         int count = atomic.load();
-#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
+#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
         if (count == 0) // !isSharable
             return false;
 #endif
@@ -58,7 +58,7 @@ public:
 
     inline bool deref() Q_DECL_NOTHROW {
         int count = atomic.load();
-#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
+#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
         if (count == 0) // !isSharable
             return false;
 #endif
@@ -67,7 +67,7 @@ public:
         return atomic.deref();
     }
 
-#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
+#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
     bool setSharable(bool sharable) Q_DECL_NOTHROW
     {
         Q_ASSERT(!isShared());
diff --git a/src/corelib/tools/qset.h b/src/corelib/tools/qset.h
index 3f4208e8b3..7e7eb5210c 100644
--- a/src/corelib/tools/qset.h
+++ b/src/corelib/tools/qset.h
@@ -79,7 +79,7 @@ public:
 
     inline void detach() { q_hash.detach(); }
     inline bool isDetached() const { return q_hash.isDetached(); }
-#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
+#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
     inline void setSharable(bool sharable) { q_hash.setSharable(sharable); }
 #endif
 
diff --git a/src/corelib/tools/qvector.h b/src/corelib/tools/qvector.h
index 691872cb36..3154220634 100644
--- a/src/corelib/tools/qvector.h
+++ b/src/corelib/tools/qvector.h
@@ -100,7 +100,7 @@ public:
 
     inline void detach();
     inline bool isDetached() const { return !d->ref.isShared(); }
-#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
+#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
     inline void setSharable(bool sharable)
     {
         if (sharable == d->ref.isSharable())
@@ -376,7 +376,7 @@ template <typename T>
 void QVector<T>::detach()
 {
     if (!isDetached()) {
-#if QT_SUPPORTS(UNSHARABLE_CONTAINERS)
+#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
         if (!d->alloc)
             d = Data::unsharableEmpty();
         else
@@ -533,7 +533,7 @@ 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)
+#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
                 Q_ASSERT(x->ref.isSharable() || options.testFlag(QArrayData::Unsharable));
 #endif
                 Q_ASSERT(!x->ref.isStatic());
@@ -601,7 +601,7 @@ 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)
+#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
     Q_ASSERT(d != Data::unsharableEmpty());
 #endif
     Q_ASSERT(aalloc ? d != Data::sharedNull() : d == Data::sharedNull());