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qatomic_cxx11: fix fetchAndAdd*()

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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>
This commit is contained in:
Marc Mutz 2013-09-18 16:21:35 +02:00 committed by The Qt Project
parent 9efa71ac0a
commit 129a8ce389
1 changed files with 4 additions and 8 deletions
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12
src/corelib/arch/qatomic_cxx11.h
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@ -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);
}
};