使用c++11实现无锁队列

以下是使用C11实现无锁队列的示例代码：

#include <stdatomic.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>

typedef struct {
    uintmax_t capacity;
    atomic_uintptr_t head;
    atomic_uintptr_t tail;
    void *entries[];
} queue_t;

queue_t *queue_create(uintmax_t capacity)
{
    queue_t *q = malloc(sizeof(queue_t) + capacity * sizeof(void *));
    if (q == NULL) {
        return NULL;
    }
    q->capacity = capacity;
    atomic_init(&q->head, (uintptr_t) q);
    atomic_init(&q->tail, (uintptr_t) q);
    return q;
}

void queue_destroy(queue_t *q)
{
    free(q);
}

bool queue_push(queue_t *q, void *entry)
{
    uintptr_t tail = atomic_load_explicit(&q->tail, memory_order_relaxed);
    for (;;) {
        queue_t *tail_ptr = (queue_t *) tail;
        uintptr_t head = atomic_load_explicit(&q->head, memory_order_acquire);
        if (tail_ptr == (queue_t *) atomic_load_explicit(&q->tail, memory_order_relaxed)) {
            if (head == (uintptr_t) tail_ptr) {
                if (atomic_compare_exchange_weak_explicit(&q->head, &head, (uintptr_t) tail_ptr->entries, memory_order_release, memory_order_acquire)) {
                    tail_ptr->entries[0] = entry;
                    atomic_store_explicit(&q->tail, (uintptr_t) (tail_ptr->entries + 1), memory_order_release);
                    return true;
                }
            } else {
                uintptr_t tail_index = (uintptr_t) tail % q->capacity;
                if (atomic_compare_exchange_weak_explicit(&q->tail, &tail, (uintptr_t) (tail_ptr->entries + ((tail_index + 1) % q->capacity)), memory_order_release, memory_order_relaxed)) {
                    tail_ptr->entries[tail_index] = entry;
                    return true;
                }
            }
        }
    }
}

bool queue_pop(queue_t *q, void **entry)
{
    uintptr_t head = atomic_load_explicit(&q->head, memory_order_relaxed);
    for (;;) {
        queue_t *head_ptr = (queue_t *) head;
        uintptr_t tail = atomic_load_explicit(&q->tail, memory_order_acquire);
        if (head_ptr == (queue_t *) atomic_load_explicit(&q->head, memory_order_relaxed)) {
            if (head_ptr == (queue_t *) tail) {
                return false;
            }
            uintptr_t head_index = (uintptr_t) head % q->capacity;
            *entry = head_ptr->entries[head_index];
            if (atomic_compare_exchange_weak_explicit(&q->head, &head, (uintptr_t) (head_ptr->entries + ((head_index + 1) % q->capacity)), memory_order_release, memory_order_relaxed)) {
                return true;
            }
        }
    }
}

该实现使用两个原子指针来跟踪队列的头尾。在队列满时，使用一个额外的指针数组来存储条目。使用`memory_order_acquire`和`memory_order_release`来确保原子操作的顺序，以避免不正确的共享内存问题。