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// This header provides cross-platform low-level atomic operations

// similar to C11 atomics.

// Operations are sequentially consistent unless they have a suffix indicating

// otherwise. If in doubt, prefer the sequentially consistent operations.

// The "_relaxed" suffix for load and store operations indicates the "relaxed"

// memory order. They don't provide synchronization, but (roughly speaking)

// guarantee somewhat sane behavior for races instead of undefined behavior.

// In practice, they correspond to "normal" hardware load and store

// instructions, so they are almost as inexpensive as plain loads and stores

// in C.

// Note that atomic read-modify-write operations like _Py_atomic_add_* return

// the previous value of the atomic variable, not the new value.

// See https://en.cppreference.com/w/c/atomic for more information on C11

// atomics.

// See https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p2055r0.pdf

// "A Relaxed Guide to memory_order_relaxed" for discussion of and common usage

// or relaxed atomics.

// Functions with pseudo Python code:

// def _Py_atomic_load(obj):

// return obj # sequential consistency

// def _Py_atomic_load_relaxed(obj):

// return obj # relaxed consistency

// def _Py_atomic_store(obj, value):

// obj = value # sequential consistency

// def _Py_atomic_store_relaxed(obj, value):

// obj = value # relaxed consistency

// def _Py_atomic_exchange(obj, value):

// # sequential consistency

// old_obj = obj

// obj = value

// return old_obj

// def _Py_atomic_compare_exchange(obj, expected, desired):

// # sequential consistency

// if obj == expected:

// obj = desired

// return True

// else:

// expected = obj

// return False

// def _Py_atomic_add(obj, value):

// # sequential consistency

// old_obj = obj

// obj += value

// return old_obj

// def _Py_atomic_and(obj, value):

// # sequential consistency

// old_obj = obj

// obj &= value

// return old_obj

// def _Py_atomic_or(obj, value):

// # sequential consistency

// old_obj = obj

// obj |= value

// return old_obj

// Other functions:

// def _Py_atomic_load_ptr_acquire(obj):

// return obj # acquire

// def _Py_atomic_store_ptr_release(obj, value):

// obj = value # release

// def _Py_atomic_fence_seq_cst():

// # sequential consistency

// ...

// def _Py_atomic_fence_release():

// # release

// ...

#ifndef Py_CPYTHON_ATOMIC_H

# error "this header file must not be included directly"

#endif

// --- _Py_atomic_add --------------------------------------------------------

// Atomically adds `value` to `obj` and returns the previous value

static inline int

_Py_atomic_add_int(int *obj, int value);

static inline int8_t

_Py_atomic_add_int8(int8_t *obj, int8_t value);

static inline int16_t

_Py_atomic_add_int16(int16_t *obj, int16_t value);

static inline int32_t

_Py_atomic_add_int32(int32_t *obj, int32_t value);

static inline int64_t

_Py_atomic_add_int64(int64_t *obj, int64_t value);

static inline intptr_t

_Py_atomic_add_intptr(intptr_t *obj, intptr_t value);

static inline unsigned int

_Py_atomic_add_uint(unsigned int *obj, unsigned int value);

static inline uint8_t

_Py_atomic_add_uint8(uint8_t *obj, uint8_t value);

static inline uint16_t

_Py_atomic_add_uint16(uint16_t *obj, uint16_t value);

static inline uint32_t

_Py_atomic_add_uint32(uint32_t *obj, uint32_t value);

static inline uint64_t

_Py_atomic_add_uint64(uint64_t *obj, uint64_t value);

static inline uintptr_t

_Py_atomic_add_uintptr(uintptr_t *obj, uintptr_t value);

static inline Py_ssize_t

_Py_atomic_add_ssize(Py_ssize_t *obj, Py_ssize_t value);

// --- _Py_atomic_compare_exchange -------------------------------------------

// Performs an atomic compare-and-exchange.

// - If `*obj` and `*expected` are equal, store `desired` into `*obj`

// and return 1 (success).

// - Otherwise, store the `*obj` current value into `*expected`

// and return 0 (failure).

// These correspond to the C11 atomic_compare_exchange_strong() function.

static inline int

_Py_atomic_compare_exchange_int(int *obj, int *expected, int desired);

static inline int

_Py_atomic_compare_exchange_int8(int8_t *obj, int8_t *expected, int8_t desired);

static inline int

_Py_atomic_compare_exchange_int16(int16_t *obj, int16_t *expected, int16_t desired);

static inline int

_Py_atomic_compare_exchange_int32(int32_t *obj, int32_t *expected, int32_t desired);

static inline int

_Py_atomic_compare_exchange_int64(int64_t *obj, int64_t *expected, int64_t desired);

static inline int

_Py_atomic_compare_exchange_intptr(intptr_t *obj, intptr_t *expected, intptr_t desired);

static inline int

_Py_atomic_compare_exchange_uint(unsigned int *obj, unsigned int *expected, unsigned int desired);

static inline int

_Py_atomic_compare_exchange_uint8(uint8_t *obj, uint8_t *expected, uint8_t desired);

static inline int

_Py_atomic_compare_exchange_uint16(uint16_t *obj, uint16_t *expected, uint16_t desired);

static inline int

_Py_atomic_compare_exchange_uint32(uint32_t *obj, uint32_t *expected, uint32_t desired);

static inline int

_Py_atomic_compare_exchange_uint64(uint64_t *obj, uint64_t *expected, uint64_t desired);

static inline int

_Py_atomic_compare_exchange_uintptr(uintptr_t *obj, uintptr_t *expected, uintptr_t desired);

static inline int

_Py_atomic_compare_exchange_ssize(Py_ssize_t *obj, Py_ssize_t *expected, Py_ssize_t desired);

// NOTE: `obj` and `expected` are logically `void**` types, but we use `void*`

// so that we can pass types like `PyObject**` without a cast.

static inline int

_Py_atomic_compare_exchange_ptr(void *obj, void *expected, void *value);

// --- _Py_atomic_exchange ---------------------------------------------------

// Atomically replaces `*obj` with `value` and returns the previous value of `*obj`.

static inline int

_Py_atomic_exchange_int(int *obj, int value);

static inline int8_t

_Py_atomic_exchange_int8(int8_t *obj, int8_t value);

static inline int16_t

_Py_atomic_exchange_int16(int16_t *obj, int16_t value);

static inline int32_t

_Py_atomic_exchange_int32(int32_t *obj, int32_t value);

static inline int64_t

_Py_atomic_exchange_int64(int64_t *obj, int64_t value);

static inline intptr_t

_Py_atomic_exchange_intptr(intptr_t *obj, intptr_t value);

static inline unsigned int

_Py_atomic_exchange_uint(unsigned int *obj, unsigned int value);

static inline uint8_t

_Py_atomic_exchange_uint8(uint8_t *obj, uint8_t value);

static inline uint16_t

_Py_atomic_exchange_uint16(uint16_t *obj, uint16_t value);

static inline uint32_t

_Py_atomic_exchange_uint32(uint32_t *obj, uint32_t value);

static inline uint64_t

_Py_atomic_exchange_uint64(uint64_t *obj, uint64_t value);

static inline uintptr_t

_Py_atomic_exchange_uintptr(uintptr_t *obj, uintptr_t value);

static inline Py_ssize_t

_Py_atomic_exchange_ssize(Py_ssize_t *obj, Py_ssize_t value);

static inline void *

_Py_atomic_exchange_ptr(void *obj, void *value);

// --- _Py_atomic_and --------------------------------------------------------

// Performs `*obj &= value` atomically and returns the previous value of `*obj`.

static inline uint8_t

_Py_atomic_and_uint8(uint8_t *obj, uint8_t value);

static inline uint16_t

_Py_atomic_and_uint16(uint16_t *obj, uint16_t value);

static inline uint32_t

_Py_atomic_and_uint32(uint32_t *obj, uint32_t value);

static inline uint64_t

_Py_atomic_and_uint64(uint64_t *obj, uint64_t value);

static inline uintptr_t

_Py_atomic_and_uintptr(uintptr_t *obj, uintptr_t value);

// --- _Py_atomic_or ---------------------------------------------------------

// Performs `*obj |= value` atomically and returns the previous value of `*obj`.

static inline uint8_t

_Py_atomic_or_uint8(uint8_t *obj, uint8_t value);

static inline uint16_t

_Py_atomic_or_uint16(uint16_t *obj, uint16_t value);

static inline uint32_t

_Py_atomic_or_uint32(uint32_t *obj, uint32_t value);

static inline uint64_t

_Py_atomic_or_uint64(uint64_t *obj, uint64_t value);

static inline uintptr_t

_Py_atomic_or_uintptr(uintptr_t *obj, uintptr_t value);

// --- _Py_atomic_load -------------------------------------------------------

// Atomically loads `*obj` (sequential consistency)

static inline int

_Py_atomic_load_int(const int *obj);

static inline int8_t

_Py_atomic_load_int8(const int8_t *obj);

static inline int16_t

_Py_atomic_load_int16(const int16_t *obj);

static inline int32_t

_Py_atomic_load_int32(const int32_t *obj);

static inline int64_t

_Py_atomic_load_int64(const int64_t *obj);

static inline intptr_t

_Py_atomic_load_intptr(const intptr_t *obj);

static inline uint8_t

_Py_atomic_load_uint8(const uint8_t *obj);

static inline uint16_t

_Py_atomic_load_uint16(const uint16_t *obj);

static inline uint32_t

_Py_atomic_load_uint32(const uint32_t *obj);

static inline uint64_t

_Py_atomic_load_uint64(const uint64_t *obj);

static inline uintptr_t

_Py_atomic_load_uintptr(const uintptr_t *obj);

static inline unsigned int

_Py_atomic_load_uint(const unsigned int *obj);

static inline Py_ssize_t

_Py_atomic_load_ssize(const Py_ssize_t *obj);

static inline void *

_Py_atomic_load_ptr(const void *obj);

// --- _Py_atomic_load_relaxed -----------------------------------------------

// Loads `*obj` (relaxed consistency, i.e., no ordering)

static inline int

_Py_atomic_load_int_relaxed(const int *obj);

static inline char

_Py_atomic_load_char_relaxed(const char *obj);

static inline unsigned char

_Py_atomic_load_uchar_relaxed(const unsigned char *obj);

static inline short

_Py_atomic_load_short_relaxed(const short *obj);

static inline unsigned short

_Py_atomic_load_ushort_relaxed(const unsigned short *obj);

static inline long

_Py_atomic_load_long_relaxed(const long *obj);

static inline double

_Py_atomic_load_double_relaxed(const double *obj);

static inline long long

_Py_atomic_load_llong_relaxed(const long long *obj);

static inline int8_t

_Py_atomic_load_int8_relaxed(const int8_t *obj);

static inline int16_t

_Py_atomic_load_int16_relaxed(const int16_t *obj);

static inline int32_t

_Py_atomic_load_int32_relaxed(const int32_t *obj);

static inline int64_t

_Py_atomic_load_int64_relaxed(const int64_t *obj);

static inline intptr_t

_Py_atomic_load_intptr_relaxed(const intptr_t *obj);

static inline uint8_t

_Py_atomic_load_uint8_relaxed(const uint8_t *obj);

static inline uint16_t

_Py_atomic_load_uint16_relaxed(const uint16_t *obj);

static inline uint32_t

_Py_atomic_load_uint32_relaxed(const uint32_t *obj);

static inline uint64_t

_Py_atomic_load_uint64_relaxed(const uint64_t *obj);

static inline uintptr_t

_Py_atomic_load_uintptr_relaxed(const uintptr_t *obj);

static inline unsigned int

_Py_atomic_load_uint_relaxed(const unsigned int *obj);

static inline Py_ssize_t

_Py_atomic_load_ssize_relaxed(const Py_ssize_t *obj);

static inline void *

_Py_atomic_load_ptr_relaxed(const void *obj);

static inline unsigned long long

_Py_atomic_load_ullong_relaxed(const unsigned long long *obj);

// --- _Py_atomic_store ------------------------------------------------------

// Atomically performs `*obj = value` (sequential consistency)

static inline void

_Py_atomic_store_int(int *obj, int value);

static inline void

_Py_atomic_store_int8(int8_t *obj, int8_t value);

static inline void

_Py_atomic_store_int16(int16_t *obj, int16_t value);

static inline void

_Py_atomic_store_int32(int32_t *obj, int32_t value);

static inline void

_Py_atomic_store_int64(int64_t *obj, int64_t value);

static inline void

_Py_atomic_store_intptr(intptr_t *obj, intptr_t value);

static inline void

_Py_atomic_store_uint8(uint8_t *obj, uint8_t value);

static inline void

_Py_atomic_store_uint16(uint16_t *obj, uint16_t value);

static inline void

_Py_atomic_store_uint32(uint32_t *obj, uint32_t value);

static inline void

_Py_atomic_store_uint64(uint64_t *obj, uint64_t value);

static inline void

_Py_atomic_store_uintptr(uintptr_t *obj, uintptr_t value);

static inline void

_Py_atomic_store_uint(unsigned int *obj, unsigned int value);

static inline void

_Py_atomic_store_ptr(void *obj, void *value);

static inline void

_Py_atomic_store_ssize(Py_ssize_t* obj, Py_ssize_t value);

// --- _Py_atomic_store_relaxed ----------------------------------------------

// Stores `*obj = value` (relaxed consistency, i.e., no ordering)

static inline void

_Py_atomic_store_int_relaxed(int *obj, int value);

static inline void

_Py_atomic_store_int8_relaxed(int8_t *obj, int8_t value);

static inline void

_Py_atomic_store_int16_relaxed(int16_t *obj, int16_t value);

static inline void

_Py_atomic_store_int32_relaxed(int32_t *obj, int32_t value);

static inline void

_Py_atomic_store_int64_relaxed(int64_t *obj, int64_t value);

static inline void

_Py_atomic_store_intptr_relaxed(intptr_t *obj, intptr_t value);

static inline void

_Py_atomic_store_uint8_relaxed(uint8_t* obj, uint8_t value);

static inline void

_Py_atomic_store_uint16_relaxed(uint16_t *obj, uint16_t value);

static inline void

_Py_atomic_store_uint32_relaxed(uint32_t *obj, uint32_t value);

static inline void

_Py_atomic_store_uint64_relaxed(uint64_t *obj, uint64_t value);

static inline void

_Py_atomic_store_uintptr_relaxed(uintptr_t *obj, uintptr_t value);

static inline void

_Py_atomic_store_uint_relaxed(unsigned int *obj, unsigned int value);

static inline void

_Py_atomic_store_ptr_relaxed(void *obj, void *value);

static inline void

_Py_atomic_store_ssize_relaxed(Py_ssize_t *obj, Py_ssize_t value);

static inline void

_Py_atomic_store_ullong_relaxed(unsigned long long *obj,

unsigned long long value);

static inline void

_Py_atomic_store_char_relaxed(char *obj, char value);

static inline void

_Py_atomic_store_uchar_relaxed(unsigned char *obj, unsigned char value);

static inline void

_Py_atomic_store_short_relaxed(short *obj, short value);

static inline void

_Py_atomic_store_ushort_relaxed(unsigned short *obj, unsigned short value);

static inline void

_Py_atomic_store_long_relaxed(long *obj, long value);

static inline void

_Py_atomic_store_float_relaxed(float *obj, float value);

static inline void

_Py_atomic_store_double_relaxed(double *obj, double value);

static inline void

_Py_atomic_store_llong_relaxed(long long *obj, long long value);

// --- _Py_atomic_load_ptr_acquire / _Py_atomic_store_ptr_release ------------

// Loads `*obj` (acquire operation)

static inline void *

_Py_atomic_load_ptr_acquire(const void *obj);

static inline uintptr_t

_Py_atomic_load_uintptr_acquire(const uintptr_t *obj);

// Stores `*obj = value` (release operation)

static inline void

_Py_atomic_store_ptr_release(void *obj, void *value);

static inline void

_Py_atomic_store_uintptr_release(uintptr_t *obj, uintptr_t value);

static inline void

_Py_atomic_store_ssize_release(Py_ssize_t *obj, Py_ssize_t value);

static inline void

_Py_atomic_store_int8_release(int8_t *obj, int8_t value);

static inline void

_Py_atomic_store_int_release(int *obj, int value);

static inline int

_Py_atomic_load_int_acquire(const int *obj);

static inline void

_Py_atomic_store_uint_release(unsigned int *obj, unsigned int value);

static inline void

_Py_atomic_store_uint32_release(uint32_t *obj, uint32_t value);

static inline void

_Py_atomic_store_uint64_release(uint64_t *obj, uint64_t value);

static inline uint64_t

_Py_atomic_load_uint64_acquire(const uint64_t *obj);

static inline uint32_t

_Py_atomic_load_uint32_acquire(const uint32_t *obj);

static inline Py_ssize_t

_Py_atomic_load_ssize_acquire(const Py_ssize_t *obj);

// --- _Py_atomic_fence ------------------------------------------------------

// Sequential consistency fence. C11 fences have complex semantics. When

// possible, use the atomic operations on variables defined above, which

// generally do not require explicit use of a fence.

// See https://en.cppreference.com/w/cpp/atomic/atomic_thread_fence

static inline void _Py_atomic_fence_seq_cst(void);

// Acquire fence

static inline void _Py_atomic_fence_acquire(void);

// Release fence

static inline void _Py_atomic_fence_release(void);

#ifndef _Py_USE_GCC_BUILTIN_ATOMICS

# if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8))

# define _Py_USE_GCC_BUILTIN_ATOMICS 1

# elif defined(__clang__)

# if __has_builtin(__atomic_load)

# define _Py_USE_GCC_BUILTIN_ATOMICS 1

# endif

#endif

#if _Py_USE_GCC_BUILTIN_ATOMICS

# define Py_ATOMIC_GCC_H

# include "pyatomic_gcc.h"

# undef Py_ATOMIC_GCC_H

#elif __STDC_VERSION__ >= 201112L && !defined(__STDC_NO_ATOMICS__)

# define Py_ATOMIC_STD_H

# include "pyatomic_std.h"

# undef Py_ATOMIC_STD_H

#elif defined(_MSC_VER)

# define Py_ATOMIC_MSC_H

# include "pyatomic_msc.h"

# undef Py_ATOMIC_MSC_H

#else

# error "no available pyatomic implementation for this platform/compiler"

#endif

// --- aliases ---------------------------------------------------------------

// Compilers don't really support "consume" semantics, so we fake it. Use

// "acquire" with TSan to support false positives. Use "relaxed" otherwise,

// because CPUs on all platforms we support respect address dependencies without

// extra barriers.

// See 2.6.7 in https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p2055r0.pdf

#if defined(_Py_THREAD_SANITIZER)

# define _Py_atomic_load_ptr_consume _Py_atomic_load_ptr_acquire

#else

# define _Py_atomic_load_ptr_consume _Py_atomic_load_ptr_relaxed

#endif

#if SIZEOF_LONG == 8

# define _Py_atomic_load_ulong(p) \

_Py_atomic_load_uint64((uint64_t *)p)

# define _Py_atomic_load_ulong_relaxed(p) \

_Py_atomic_load_uint64_relaxed((uint64_t *)p)

# define _Py_atomic_store_ulong(p, v) \

_Py_atomic_store_uint64((uint64_t *)p, v)

# define _Py_atomic_store_ulong_relaxed(p, v) \

_Py_atomic_store_uint64_relaxed((uint64_t *)p, v)

#elif SIZEOF_LONG == 4

# define _Py_atomic_load_ulong(p) \

_Py_atomic_load_uint32((uint32_t *)p)

# define _Py_atomic_load_ulong_relaxed(p) \

_Py_atomic_load_uint32_relaxed((uint32_t *)p)

# define _Py_atomic_store_ulong(p, v) \

_Py_atomic_store_uint32((uint32_t *)p, v)

# define _Py_atomic_store_ulong_relaxed(p, v) \

_Py_atomic_store_uint32_relaxed((uint32_t *)p, v)

#else

# error "long must be 4 or 8 bytes in size"

#endif // SIZEOF_LONG

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pyatomic.h

pyatomic.h

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