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/* Atomic functions: similar to pycore_atomic.h, but don't need
to declare variables as atomic.
Py_ssize_t type:
* value = _Py_atomic_size_get(&var)
* _Py_atomic_size_set(&var, value)
Use sequentially-consistent ordering (__ATOMIC_SEQ_CST memory order):
enforce total ordering with all other atomic functions.
*/
#ifndef Py_ATOMIC_FUNC_H
#define Py_ATOMIC_FUNC_H
#ifdef __cplusplus
extern "C" {
#endif
#ifndef Py_BUILD_CORE
# error "this header requires Py_BUILD_CORE define"
#endif
#if defined(_MSC_VER)
# include <intrin.h> // _InterlockedExchange()
#endif
// Use builtin atomic operations in GCC >= 4.7 and clang
#ifdef HAVE_BUILTIN_ATOMIC
static inline Py_ssize_t _Py_atomic_size_get(Py_ssize_t *var)
{
return __atomic_load_n(var, __ATOMIC_SEQ_CST);
}
static inline void _Py_atomic_size_set(Py_ssize_t *var, Py_ssize_t value)
{
__atomic_store_n(var, value, __ATOMIC_SEQ_CST);
}
#elif defined(_MSC_VER)
static inline Py_ssize_t _Py_atomic_size_get(Py_ssize_t *var)
{
#if SIZEOF_VOID_P == 8
Py_BUILD_ASSERT(sizeof(__int64) == sizeof(*var));
volatile __int64 *volatile_var = (volatile __int64 *)var;
__int64 old;
do {
old = *volatile_var;
} while(_InterlockedCompareExchange64(volatile_var, old, old) != old);
#else
Py_BUILD_ASSERT(sizeof(long) == sizeof(*var));
volatile long *volatile_var = (volatile long *)var;
long old;
do {
old = *volatile_var;
} while(_InterlockedCompareExchange(volatile_var, old, old) != old);
#endif
return old;
}
static inline void _Py_atomic_size_set(Py_ssize_t *var, Py_ssize_t value)
{
#if SIZEOF_VOID_P == 8
Py_BUILD_ASSERT(sizeof(__int64) == sizeof(*var));
volatile __int64 *volatile_var = (volatile __int64 *)var;
_InterlockedExchange64(volatile_var, value);
#else
Py_BUILD_ASSERT(sizeof(long) == sizeof(*var));
volatile long *volatile_var = (volatile long *)var;
_InterlockedExchange(volatile_var, value);
#endif
}
#else
// Fallback implementation using volatile
static inline Py_ssize_t _Py_atomic_size_get(Py_ssize_t *var)
{
volatile Py_ssize_t *volatile_var = (volatile Py_ssize_t *)var;
return *volatile_var;
}
static inline void _Py_atomic_size_set(Py_ssize_t *var, Py_ssize_t value)
{
volatile Py_ssize_t *volatile_var = (volatile Py_ssize_t *)var;
*volatile_var = value;
}
#endif
#ifdef __cplusplus
}
#endif
#endif /* Py_ATOMIC_FUNC_H */
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