Silence MSVC warnings when using certain std algorithms

The MSVC STL warns when passing naked pointers as non-bounded
iterators to algorithms such as std::equal and std::copy, in
an attempt to inform users that the range specified by that
iterator has an implicit minimum size that the caller of the
algorithm must ensure is met:

  warning C4996: 'std::_Equal1': Function call with parameters that may be unsafe - \
  this call relies on the caller to check that the passed values are correct. To \
  disable this warning, use -D_SCL_SECURE_NO_WARNINGS. See documentation on how to \
  use Visual C++ 'Checked Iterators'

When building Qt, as well as when building user projects with
qmake (cf. 0a76b6bc7f), we
globally disable this warning (with -D_SCL_SECURE_NO_WARNINGS),
but since we started using STL algorithms in public headers (e.g.
in qvector.h), users get this warning in their own projects now,
unless they, too, define said macro. But such a requirement is
against the Qt policy to have headers that are warning-free as
much as possible.

The suggested way of fixing this warning is to wrap the naked
pointer in a stdext::unchecked_array_iterator before passing it
to the algorithm, cf. examples in

  https://msdn.microsoft.com/en-us/library/ttcz0bys%28v=vs.120%29.aspx

or, together with the capacity-made-explicit, in a
stdext::checked_array_iterator.

To avoid ifdefs for platforms that don't have these extensions
(which, incidentally, for the unchecked case, includes MSVC 2012),
wrap the calls in macros.

The end game here is to drop -D_SCL_SECURE_NO_WARNINGS, at least
for public headers, even though this commit also adds the wrapper
to implementation and private header files.

An alternative to the wrapper would have been the version of
std::equal that takes four iterators. However, that is a C++14
library feature, while this version of Qt still needs to compile
with a C++98 compiler, and, more importantly, there isn't, and
never will be, a corresponding 4-iterator version of std::copy.

Task-number: QTBUG-47948
Done-with: Stephen Kelly <steveire@gmail.com>
Change-Id: I1bbab257fb5f1c5042939c382a412b596112ff26
Reviewed-by: Stephen Kelly <ske@ableton.com>

src/corelib/global/qcompilerdetection.h

@@ -94,6 +94,12 @@
 #  define Q_DECL_DEPRECATED_X(text) __declspec(deprecated(text))
 #  define Q_DECL_EXPORT __declspec(dllexport)
 #  define Q_DECL_IMPORT __declspec(dllimport)
+#  if _MSC_VER >= 1800
+#    define QT_MAKE_UNCHECKED_ARRAY_ITERATOR(x) stdext::make_unchecked_array_iterator(x)
+#  endif
+#  if _MSC_VER >= 1500
+#    define QT_MAKE_CHECKED_ARRAY_ITERATOR(x, N) stdext::make_checked_array_iterator(x, size_t(N))
+#  endif
 /* Intel C++ disguising as Visual C++: the `using' keyword avoids warnings */
 #  if defined(__INTEL_COMPILER)
 #    define Q_DECL_VARIABLE_DEPRECATED
@@ -1117,6 +1123,12 @@
 #ifndef Q_DECL_CONST_FUNCTION
 #  define Q_DECL_CONST_FUNCTION Q_DECL_PURE_FUNCTION
 #endif
+#ifndef QT_MAKE_UNCHECKED_ARRAY_ITERATOR
+#  define QT_MAKE_UNCHECKED_ARRAY_ITERATOR(x) (x)
+#endif
+#ifndef QT_MAKE_CHECKED_ARRAY_ITERATOR
+#  define QT_MAKE_CHECKED_ARRAY_ITERATOR(x, N) (x)
+#endif
 
 /*
  * Warning/diagnostic handling

src/corelib/kernel/qcoreapplication.cpp

@@ -444,7 +444,7 @@ QCoreApplicationPrivate::QCoreApplicationPrivate(int &aargc, char **aargv, uint
     if (!isArgvModified(argc, argv)) {
         origArgc = argc;
         origArgv = new char *[argc];
-        std::copy(argv, argv + argc, origArgv);
+        std::copy(argv, argv + argc, QT_MAKE_CHECKED_ARRAY_ITERATOR(origArgv, argc));
     }
 #endif // Q_OS_WIN && !Q_OS_WINRT
 

src/corelib/tools/qlist.h

@@ -846,7 +846,7 @@ inline bool QList<T>::op_eq_impl(const QList &l, QListData::ArrayCompatibleLayou
     const T *lb = reinterpret_cast<const T*>(l.p.begin());
     const T *b  = reinterpret_cast<const T*>(p.begin());
     const T *e  = reinterpret_cast<const T*>(p.end());
-    return std::equal(b, e, lb);
+    return std::equal(b, e, QT_MAKE_CHECKED_ARRAY_ITERATOR(lb, l.p.size()));
 }
 
 template <typename T>

src/corelib/tools/qvarlengtharray.h

@@ -96,7 +96,8 @@ public:
     QVarLengthArray<T, Prealloc> &operator=(std::initializer_list<T> list)
     {
         resize(list.size());
-        std::copy(list.begin(), list.end(), this->begin());
+        std::copy(list.begin(), list.end(),
+                  QT_MAKE_CHECKED_ARRAY_ITERATOR(this->begin(), this->size()));
         return *this;
     }
 #endif
@@ -467,7 +468,7 @@ Q_OUTOFLINE_TEMPLATE typename QVarLengthArray<T, Prealloc>::iterator QVarLengthA
     int l = int(aend - ptr);
     int n = l - f;
     if (QTypeInfo<T>::isComplex) {
-        std::copy(ptr + l, ptr + s, ptr + f);
+        std::copy(ptr + l, ptr + s, QT_MAKE_CHECKED_ARRAY_ITERATOR(ptr + f, s - f));
         T *i = ptr + s;
         T *b = ptr + s - n;
         while (i != b) {
@@ -489,7 +490,7 @@ bool operator==(const QVarLengthArray<T, Prealloc1> &l, const QVarLengthArray<T,
     const T *rb = r.begin();
     const T *b  = l.begin();
     const T *e  = l.end();
-    return std::equal(b, e, rb);
+    return std::equal(b, e, QT_MAKE_CHECKED_ARRAY_ITERATOR(rb, r.size()));
 }
 
 template <typename T, int Prealloc1, int Prealloc2>

src/corelib/tools/qvector.h

@@ -767,7 +767,7 @@ bool QVector<T>::operator==(const QVector<T> &v) const
     const T *vb = v.d->begin();
     const T *b  = d->begin();
     const T *e  = d->end();
-    return std::equal(b, e, vb);
+    return std::equal(b, e, QT_MAKE_CHECKED_ARRAY_ITERATOR(vb, v.d->size));
 }
 
 template <typename T>

src/gui/kernel/qkeysequence.cpp

@@ -1637,7 +1637,7 @@ QDataStream &operator>>(QDataStream &s, QKeySequence &keysequence)
         s >> keys[i];
     }
     qAtomicDetach(keysequence.d);
-    std::copy(keys, keys + MaxKeys, keysequence.d->key);
+    std::copy(keys, keys + MaxKeys, QT_MAKE_CHECKED_ARRAY_ITERATOR(keysequence.d->key, MaxKeys));
     return s;
 }
 

src/gui/kernel/qkeysequence_p.h

@@ -70,7 +70,8 @@ public:
     }
     inline QKeySequencePrivate(const QKeySequencePrivate &copy) : ref(1)
     {
-        std::copy(copy.key, copy.key + MaxKeyCount, key);
+        std::copy(copy.key, copy.key + MaxKeyCount,
+                  QT_MAKE_CHECKED_ARRAY_ITERATOR(key, MaxKeyCount));
     }
     QAtomicInt ref;
     int key[MaxKeyCount];

src/plugins/platforms/windows/accessible/iaccessible2.cpp

@@ -602,7 +602,8 @@ HRESULT STDMETHODCALLTYPE QWindowsIA2Accessible::get_keyBinding(long actionIndex
             // The IDL documents that the client must free with CoTaskMemFree
             arrayOfBindingsToReturn = coTaskMemAllocArray<BSTR>(numBindings);
             std::transform(keyBindings.constBegin(), keyBindings.constEnd(),
-                           arrayOfBindingsToReturn, QStringToBSTR);
+                           QT_MAKE_CHECKED_ARRAY_ITERATOR(arrayOfBindingsToReturn, numBindings),
+                           QStringToBSTR);
         }
     }
     *keyBindings = arrayOfBindingsToReturn;
@@ -986,7 +987,8 @@ HRESULT STDMETHODCALLTYPE QWindowsIA2Accessible::get_selectedColumns(long **sele
         *selectedColumns = Q_NULLPTR;
         if (count) {
             *selectedColumns = coTaskMemAllocArray<long>(count);
-            std::copy(selectedIndices.constBegin(), selectedIndices.constEnd(), *selectedColumns);
+            std::copy(selectedIndices.constBegin(), selectedIndices.constEnd(),
+                      QT_MAKE_CHECKED_ARRAY_ITERATOR(*selectedColumns, count));
         }
         return count ? S_OK : S_FALSE;
     }
@@ -1008,7 +1010,8 @@ HRESULT STDMETHODCALLTYPE QWindowsIA2Accessible::get_selectedRows(long **selecte
         *selectedRows = Q_NULLPTR;
         if (count) {
             *selectedRows = coTaskMemAllocArray<long>(count);
-            std::copy(selectedIndices.constBegin(), selectedIndices.constEnd(), *selectedRows);
+            std::copy(selectedIndices.constBegin(), selectedIndices.constEnd(),
+                      QT_MAKE_CHECKED_ARRAY_ITERATOR(*selectedRows, count));
         }
         return count ? S_OK : S_FALSE;
     }
@@ -1677,7 +1680,8 @@ HRESULT QWindowsIA2Accessible::wrapListOfCells(const QList<QAccessibleInterface*
     if (count) {
         *outputAccessibles = coTaskMemAllocArray<IUnknown *>(count);
         std::transform(inputCells.constBegin(), inputCells.constEnd(),
-                       *outputAccessibles, QWindowsAccessibility::wrap);
+                       QT_MAKE_CHECKED_ARRAY_ITERATOR(*outputAccessibles, count),
+                       QWindowsAccessibility::wrap);
     }
     return count > 0 ? S_OK : S_FALSE;
 }

src/plugins/platforms/windows/array.h

@@ -79,7 +79,8 @@ public:
             const T *oldData = data;
             data = new T[capacity];
             if (oldData) {
-                std::copy(oldData, oldData + m_size, data);
+                std::copy(oldData, oldData + m_size,
+                          QT_MAKE_CHECKED_ARRAY_ITERATOR(data, capacity));
                 delete [] oldData;
             }
             m_capacity = capacity;

src/plugins/platforms/windows/qwindowsinputcontext.cpp

@@ -650,7 +650,7 @@ int QWindowsInputContext::reconvertString(RECONVERTSTRING *reconv)
     reconv->dwTargetStrOffset = reconv->dwCompStrOffset;
     ushort *pastReconv = reinterpret_cast<ushort *>(reconv + 1);
     std::copy(surroundingText.utf16(), surroundingText.utf16() + surroundingText.size(),
-              pastReconv);
+              QT_MAKE_UNCHECKED_ARRAY_ITERATOR(pastReconv));
     return memSize;
 }