From 5cc0de2e084cb887a75b076b82cf470ecdcd4dd3 Mon Sep 17 00:00:00 2001 From: Marc Mutz Date: Thu, 26 May 2016 08:30:26 +0200 Subject: QAtomic: pass explicit failure memory order to std::atomic::compare_exchange_strong MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit GCC 4.8 seems to get the failure memory order wrong when using the overload that only accepts one memory order and produces errors such as: bits/atomic_base.h:577:70: error: failure memory model cannot be stronger than success memory model for '__atomic_compare_exchange' return __atomic_compare_exchange_n(&_M_i, &__i1, __i2, 0, __m1, __m2); ^ (as seen on Android). Fix by explicitly passing the failure orders corresponding to the success orders, as specified by the standard: relaxed → relaxed release → relaxed acquire → acquire acq_rel → acquire (cf. http://en.cppreference.com/w/cpp/atomic/atomic/compare_exchange). Task-number: QTBUG-59399 Change-Id: If046e735888cf331d2d6506d8d5ca9aa7402f9ad Reviewed-by: David Faure Reviewed-by: Olivier Goffart (Woboq GmbH) --- src/corelib/arch/qatomic_cxx11.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/src/corelib/arch/qatomic_cxx11.h b/src/corelib/arch/qatomic_cxx11.h index 63b23b71ab..484ec73e7f 100644 --- a/src/corelib/arch/qatomic_cxx11.h +++ b/src/corelib/arch/qatomic_cxx11.h @@ -278,7 +278,7 @@ template struct QAtomicOps template static bool testAndSetRelaxed(std::atomic &_q_value, T expectedValue, T newValue, T *currentValue = Q_NULLPTR) Q_DECL_NOTHROW { - bool tmp = _q_value.compare_exchange_strong(expectedValue, newValue, std::memory_order_relaxed); + bool tmp = _q_value.compare_exchange_strong(expectedValue, newValue, std::memory_order_relaxed, std::memory_order_relaxed); if (currentValue) *currentValue = expectedValue; return tmp; @@ -287,7 +287,7 @@ template struct QAtomicOps template static bool testAndSetAcquire(std::atomic &_q_value, T expectedValue, T newValue, T *currentValue = Q_NULLPTR) Q_DECL_NOTHROW { - bool tmp = _q_value.compare_exchange_strong(expectedValue, newValue, std::memory_order_acquire); + bool tmp = _q_value.compare_exchange_strong(expectedValue, newValue, std::memory_order_acquire, std::memory_order_acquire); if (currentValue) *currentValue = expectedValue; return tmp; @@ -296,7 +296,7 @@ template struct QAtomicOps template static bool testAndSetRelease(std::atomic &_q_value, T expectedValue, T newValue, T *currentValue = Q_NULLPTR) Q_DECL_NOTHROW { - bool tmp = _q_value.compare_exchange_strong(expectedValue, newValue, std::memory_order_release); + bool tmp = _q_value.compare_exchange_strong(expectedValue, newValue, std::memory_order_release, std::memory_order_relaxed); if (currentValue) *currentValue = expectedValue; return tmp; @@ -305,7 +305,7 @@ template struct QAtomicOps template static bool testAndSetOrdered(std::atomic &_q_value, T expectedValue, T newValue, T *currentValue = Q_NULLPTR) Q_DECL_NOTHROW { - bool tmp = _q_value.compare_exchange_strong(expectedValue, newValue, std::memory_order_acq_rel); + bool tmp = _q_value.compare_exchange_strong(expectedValue, newValue, std::memory_order_acq_rel, std::memory_order_acquire); if (currentValue) *currentValue = expectedValue; return tmp; -- cgit v1.2.3