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. 0a76b6bc7f98900ea884cd10ccca1a332e5bdba5), 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>

1 files changed, 8 insertions, 4 deletions

diff --git a/src/plugins/platforms/windows/accessible/iaccessible2.cpp b/src/plugins/platforms/windows/accessible/iaccessible2.cpp
index 7abb98f385..5e0794bd95 100644
--- a/src/plugins/platforms/windows/accessible/iaccessible2.cpp
+++ b/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;
 }