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在头文件<stdatomic.h>中定义



C atomic_fetch_sub（volatile A * obj，M arg）;

(1)

（自C11以来）

C atomic_fetch_sub_explicit（volatile A * obj，M arg，memory_order order）;

(2)

（自C11以来）

将原来的值与旧的值的obj减法结果进行原子替换，并返回先前保存的值。操作是读取 - 修改 - 写入操作。第一个版本根据命令对内存进行访问，第二个版本根据内存访问内存访问。argobjobjmemory_order_seq_cstorder

这是为所有原子对象类型A定义的通用函数。参数是指向易失性原子类型的指针，以接受非易失性和易失性（例如内存映射I / O）原子变量的地址.M可以是非易失性 如果A是原子整数类型，则对应于A的原子类型;如果A是原子指针类型，则为ptrdiff_t。

对于有符号整数类型，算术定义为使用二进制补码表示。没有未定义的结果。对于指针类型，结果可能是一个未定义的地址，但操作没有未定义的行为。

参数

obj

-

指向要修改的原子对象的指针

arg

-

从存储在原子对象中的值中减去的值

order

-

此操作的内存同步排序：所有值都是允许的

返回值

由obj指向的原子对象先前保存的值。

References

  • C11标准（ISO/IEC 9899:2011）：

    • 7.17.7.5 atomic_fetch和修改泛型函数（p: 284-285）

另请参阅

atomic_fetch_addatomic_fetch_add_explicit (C11)

atomic addition  (function)

| atomic_fetch_sub，atomic_fetch_sub_explicit的C ++文档 |

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