Improvements based on feedback from Anthony Williams
This commit is contained in:
Sam Lantinga
parent
c8cd5b9028
commit
29e0bf97e0
4 changed files with 93 additions and 126 deletions
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@ -38,8 +38,13 @@
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* SDL_AtomicDecRef()
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*
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* Seriously, here be dragons!
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* ^^^^^^^^^^^^^^^^^^^^^^^^^^^
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*
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* These operations may, or may not, actually be implemented using
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* You can find out a little more about lockless programming and the
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* subtle issues that can arise here:
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* http://msdn.microsoft.com/en-us/library/ee418650%28v=vs.85%29.aspx
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*
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* These operations may or may not actually be implemented using
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* processor specific atomic operations. When possible they are
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* implemented as true processor specific atomic operations. When that
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* is not possible the are implemented using locks that *do* use the
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@ -114,66 +119,54 @@ extern DECLSPEC void SDLCALL SDL_AtomicUnlock(SDL_SpinLock *lock);
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/*@}*//*SDL AtomicLock*/
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/* The compiler barrier prevents the compiler from reordering
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reads and writes to globally visible variables across the call.
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*/
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#ifdef _MSC_VER
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void _ReadWriteBarrier(void);
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#pragma intrinsic(_ReadWriteBarrier)
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#define SDL_CompilerBarrier() _ReadWriteBarrier()
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#elif __GNUC__
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#define SDL_CompilerBarrier() __asm__ __volatile__ ("" : : : "memory")
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#else
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#define SDL_CompilerBarrier() \
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({ SDL_SpinLock _tmp = 0; SDL_AtomicLock(&_tmp); SDL_AtomicUnlock(&_tmp); })
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#endif
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/* Platform specific optimized versions of the atomic functions,
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* you can disable these by defining SDL_DISABLE_ATOMIC_INLINE
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*/
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#ifndef SDL_DISABLE_ATOMIC_INLINE
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#if defined(HAVE_MSC_ATOMICS)
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#if HAVE_MSC_ATOMICS
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#define SDL_AtomicSet(a, v) _InterlockedExchange((long*)&(a)->value, (v))
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#define SDL_AtomicGet(a) ((a)->value)
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#define SDL_AtomicAdd(a, v) _InterlockedExchangeAdd((long*)&(a)->value, (v))
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#define SDL_AtomicCAS(a, oldval, newval) (_InterlockedCompareExchange((long*)&(a)->value, (newval), (oldval)) == (oldval))
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#define SDL_AtomicSetPtr(a, v) (void)_InterlockedExchangePointer((a), (v))
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#define SDL_AtomicGetPtr(a) (*(a))
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#define SDL_AtomicSetPtr(a, v) _InterlockedExchangePointer((a), (v))
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#if _M_IX86
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#define SDL_AtomicCASPtr(a, oldval, newval) (_InterlockedCompareExchange((long*)(a), (long)(newval), (long)(oldval)) == (long)(oldval))
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#else
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#define SDL_AtomicCASPtr(a, oldval, newval) (_InterlockedCompareExchangePointer((a), (newval), (oldval)) == (oldval))
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#endif
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#elif defined(__MACOSX__)
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#elif __MACOSX__
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#include <libkern/OSAtomic.h>
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#define SDL_AtomicSet(a, v) \
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({ \
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int oldvalue; \
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\
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do { \
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oldvalue = (a)->value; \
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} while (!OSAtomicCompareAndSwap32Barrier(oldvalue, v, &(a)->value)); \
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\
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oldvalue; \
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})
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#define SDL_AtomicGet(a) ((a)->value)
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#define SDL_AtomicAdd(a, v) \
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({ \
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int oldvalue; \
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\
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do { \
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oldvalue = (a)->value; \
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} while (!OSAtomicCompareAndSwap32Barrier(oldvalue, oldvalue+v, &(a)->value)); \
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\
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oldvalue; \
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})
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#define SDL_AtomicCAS(a, oldval, newval) OSAtomicCompareAndSwap32Barrier(oldval, newval, &(a)->value)
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#define SDL_AtomicSetPtr(a, v) (*(a) = v, OSMemoryBarrier())
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#define SDL_AtomicGetPtr(a) (*(a))
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#define SDL_AtomicCAS(a, oldval, newval) OSAtomicCompareAndSwap32Barrier((oldval), (newval), &(a)->value)
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#if SIZEOF_VOIDP == 4
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#define SDL_AtomicCASPtr(a, oldval, newval) OSAtomicCompareAndSwap32Barrier((int32_t)(oldval), (int32_t)(newval), (int32_t*)(a))
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#elif SIZEOF_VOIDP == 8
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#define SDL_AtomicCASPtr(a, oldval, newval) OSAtomicCompareAndSwap64Barrier((int64_t)(oldval), (int64_t)(newval), (int64_t*)(a))
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#endif
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#elif defined(HAVE_GCC_ATOMICS)
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#elif HAVE_GCC_ATOMICS
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#define SDL_AtomicSet(a, v) __sync_lock_test_and_set(&(a)->value, v)
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#define SDL_AtomicGet(a) ((a)->value)
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#define SDL_AtomicAdd(a, v) __sync_fetch_and_add(&(a)->value, v)
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#define SDL_AtomicSetPtr(a, v) __sync_lock_test_and_set(a, v)
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#define SDL_AtomicCAS(a, oldval, newval) __sync_bool_compare_and_swap(&(a)->value, oldval, newval)
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#define SDL_AtomicSetPtr(a, v) (*(a) = v, __sync_synchronize())
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#define SDL_AtomicGetPtr(a) (*(a))
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#define SDL_AtomicCASPtr(a, oldval, newval) __sync_bool_compare_and_swap(a, oldval, newval)
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#endif
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@ -195,40 +188,61 @@ typedef struct { int value; } SDL_atomic_t;
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* \return The previous value of the atomic variable.
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*/
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#ifndef SDL_AtomicSet
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extern DECLSPEC int SDLCALL SDL_AtomicSet(SDL_atomic_t *a, int value);
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#define SDL_AtomicSet(a, v) \
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({ \
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int _value; \
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do { \
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_value = (a)->value; \
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} while (!SDL_AtomicCAS(a, _value, (v))); \
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_value; \
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})
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#endif
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/**
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* \brief Get the value of an atomic variable
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*/
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#ifndef SDL_AtomicGet
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extern DECLSPEC int SDLCALL SDL_AtomicGet(SDL_atomic_t *a);
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#define SDL_AtomicGet(a) \
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({ \
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int _value = (a)->value; \
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SDL_CompilerBarrier(); \
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_value; \
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})
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#endif
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/**
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* \brief Add to an atomic variable.
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* \brief Add to an atomic variable.
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*
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* \return The previous value of the atomic variable.
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*
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* \note This same style can be used for any number operation
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*/
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#ifndef SDL_AtomicAdd
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extern DECLSPEC int SDLCALL SDL_AtomicAdd(SDL_atomic_t *a, int value);
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#define SDL_AtomicAdd(a, v) \
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({ \
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int _value; \
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do { \
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_value = (a)->value; \
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} while (!SDL_AtomicCAS(a, _value, (_value + (v)))); \
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_value; \
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})
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#endif
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/**
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* \brief Increment an atomic variable used as a reference count.
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*/
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#ifndef SDL_AtomicIncRef
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extern DECLSPEC void SDLCALL SDL_AtomicIncRef(SDL_atomic_t *a);
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#define SDL_AtomicIncRef(a) SDL_AtomicAdd(a, 1)
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#endif
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/**
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* \brief Decrement an atomic variable used as a reference count.
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*
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* \return SDL_TRUE if the variable has reached zero after decrementing,
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* \return SDL_TRUE if the variable reached zero after decrementing,
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* SDL_FALSE otherwise
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*/
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#ifndef SDL_AtomicDecRef
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extern DECLSPEC SDL_bool SDLCALL SDL_AtomicDecRef(SDL_atomic_t *a);
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#define SDL_AtomicDecRef(a) (SDL_AtomicAdd(a, -1) == 1)
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#endif
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/**
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@ -239,21 +253,36 @@ extern DECLSPEC SDL_bool SDLCALL SDL_AtomicDecRef(SDL_atomic_t *a);
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* \note If you don't know what this function is for, you shouldn't use it!
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*/
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#ifndef SDL_AtomicCAS
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extern DECLSPEC SDL_bool SDLCALL SDL_AtomicCAS(SDL_atomic_t *a, int oldval, int newval);
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#define SDL_AtomicCAS SDL_AtomicCAS_
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#endif
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extern DECLSPEC SDL_bool SDLCALL SDL_AtomicCAS_(SDL_atomic_t *a, int oldval, int newval);
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/**
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* \brief Set a pointer to a value atomically.
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*
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* \return The previous value of the pointer.
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*/
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#ifndef SDL_AtomicSetPtr
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extern DECLSPEC void SDLCALL SDL_AtomicSetPtr(void** a, void* value);
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#define SDL_AtomicSetPtr(a, v) \
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({ \
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void* _value; \
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do { \
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_value = *(a); \
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} while (!SDL_AtomicCASPtr(a, _value, (v))); \
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_value; \
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})
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#endif
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/**
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* \brief Get the value of a pointer atomically.
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*/
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#ifndef SDL_AtomicGetPtr
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extern DECLSPEC void* SDLCALL SDL_AtomicGetPtr(void** a);
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#define SDL_AtomicGetPtr(a) \
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({ \
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void* _value = *(a); \
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SDL_CompilerBarrier(); \
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_value; \
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})
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#endif
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/**
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@ -264,8 +293,9 @@ extern DECLSPEC void* SDLCALL SDL_AtomicGetPtr(void** a);
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* \note If you don't know what this function is for, you shouldn't use it!
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*/
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#ifndef SDL_AtomicCASPtr
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extern DECLSPEC SDL_bool SDLCALL SDL_AtomicCASPtr(void **a, void *oldval, void *newval);
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#define SDL_AtomicCASPtr SDL_AtomicCASPtr_
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#endif
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extern DECLSPEC SDL_bool SDLCALL SDL_AtomicCASPtr_(void **a, void *oldval, void *newval);
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/* Ends C function definitions when using C++ */
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#ifdef __cplusplus
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