mirror of
https://github.com/wpilibsuite/allwpilib
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d90cf843e8
This is a breaking change to dependencies that use the static ntcore library. Unless the wpiutil library is also linked, linker errors will result. This does not affect the shared ntcore library.
50 lines
1.8 KiB
C++
50 lines
1.8 KiB
C++
/*----------------------------------------------------------------------------*/
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/* Copyright (c) FIRST 2015. All Rights Reserved. */
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/* Open Source Software - may be modified and shared by FRC teams. The code */
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/* must be accompanied by the FIRST BSD license file in the root directory of */
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/* the project. */
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/*----------------------------------------------------------------------------*/
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#ifndef WPIUTIL_SUPPORT_ATOMIC_STATIC_H_
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#define WPIUTIL_SUPPORT_ATOMIC_STATIC_H_
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#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
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// Just use a local static. This is thread-safe per
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// http://preshing.com/20130930/double-checked-locking-is-fixed-in-cpp11/
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// Per https://msdn.microsoft.com/en-us/library/Hh567368.aspx "Magic Statics"
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// are supported in Visual Studio 2015 but not in earlier versions.
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#define ATOMIC_STATIC(cls, inst) static cls inst
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#define ATOMIC_STATIC_DECL(cls)
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#define ATOMIC_STATIC_INIT(cls)
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#else
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// From http://preshing.com/20130930/double-checked-locking-is-fixed-in-cpp11/
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#include <atomic>
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#include <mutex>
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#define ATOMIC_STATIC(cls, inst) \
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cls* inst##tmp = m_instance.load(std::memory_order_acquire); \
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if (inst##tmp == nullptr) { \
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std::lock_guard<std::mutex> lock(m_instance_mutex); \
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inst##tmp = m_instance.load(std::memory_order_relaxed); \
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if (inst##tmp == nullptr) { \
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inst##tmp = new cls; \
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m_instance.store(inst##tmp, std::memory_order_release); \
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} \
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} \
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cls& inst = *inst##tmp
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#define ATOMIC_STATIC_DECL(cls) \
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static std::atomic<cls*> m_instance; \
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static std::mutex m_instance_mutex;
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#define ATOMIC_STATIC_INIT(cls) \
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std::atomic<cls*> cls::m_instance; \
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std::mutex cls::m_instance_mutex;
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#endif
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#endif // WPIUTIL_SUPPORT_ATOMIC_STATIC_H_
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