qatomic_cxx11: fix fetchAndAdd*()

In qatomic_cxx11, the 'Type' is std::atomic<T>, whose fetch_add method,
used in fetchAndAdd*(), already does the right thing for T* with sizeof(T) > 1.
The code, however, applied 'AddScale' to the 'valueToAdd', thus becoming
incompatible with normal pointer arithmetics.

This is very apparent when one goes to the length of actually testing
qatomic_cxx11 with tst_QAtomicPointer (which is non-trivial, since the
-c++11 configure option currently doesn't have an effect on tests/auto).

To fix, remove the AddScale factor.

Change-Id: I7507203af3b7df31d8322b31a6a1a33ca847d224
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 4 insertions, 8 deletions

diff --git a/src/corelib/arch/qatomic_cxx11.h b/src/corelib/arch/qatomic_cxx11.h
index ed19064724..55e71e1e88 100644
--- a/src/corelib/arch/qatomic_cxx11.h
+++ b/src/corelib/arch/qatomic_cxx11.h
@@ -219,29 +219,25 @@ template <typename X> struct QAtomicOps
     template <typename T> static inline
     T fetchAndAddRelaxed(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) Q_DECL_NOTHROW
     {
-        return _q_value.fetch_add(valueToAdd * QAtomicAdditiveType<T>::AddScale,
-                                  std::memory_order_relaxed);
+        return _q_value.fetch_add(valueToAdd, std::memory_order_relaxed);
     }
 
     template <typename T> static inline
     T fetchAndAddAcquire(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) Q_DECL_NOTHROW
     {
-        return _q_value.fetch_add(valueToAdd * QAtomicAdditiveType<T>::AddScale,
-                                  std::memory_order_acquire);
+        return _q_value.fetch_add(valueToAdd, std::memory_order_acquire);
     }
 
     template <typename T> static inline
     T fetchAndAddRelease(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) Q_DECL_NOTHROW
     {
-        return _q_value.fetch_add(valueToAdd * QAtomicAdditiveType<T>::AddScale,
-                                  std::memory_order_release);
+        return _q_value.fetch_add(valueToAdd, std::memory_order_release);
     }
 
     template <typename T> static inline
     T fetchAndAddOrdered(std::atomic<T> &_q_value, typename QAtomicAdditiveType<T>::AdditiveT valueToAdd) Q_DECL_NOTHROW
     {
-        return _q_value.fetch_add(valueToAdd * QAtomicAdditiveType<T>::AddScale,
-                                  std::memory_order_acq_rel);
+        return _q_value.fetch_add(valueToAdd, std::memory_order_acq_rel);
     }
 };