c语言多线程单例模式

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c语言多线程单例模式

懒汉模式：

#include <pthread.h>#include <stdio.h>pthread_once_t once = PTHREAD_ONCE_INIT;class Singleton{protected:    static Singleton *_instance;    static void mutex_init(void); //initialize mutex at beginning    static pthread_mutex_t mutex;    Singleton() {}public:    static Singleton* getInstance();};Singleton* Singleton::_instance = NULL;pthread_mutex_t Singleton::mutex;void Singleton::mutex_init(void){    printf("in mutex_init\n");    pthread_mutex_init(&mutex, NULL);}Singleton* Singleton::getInstance(){    pthread_once(&once, mutex_init);    if(_instance == NULL)    {        pthread_mutex_lock(&mutex);        if(_instance == NULL)            _instance = new Singleton();        pthread_mutex_unlock(&mutex);    }    return _instance;}void* thrFunc1(void *arg){    printf("in thrFunc1\n");    auto p = Singleton::getInstance();    printf("address: %p\n", p);    return NULL;}int main(){    pthread_t pid1, pid2;    pthread_create(&pid1, NULL, thrFunc1, NULL);    pthread_create(&pid2, NULL, thrFunc1, NULL);    pthread_join(pid1, NULL);    pthread_join(pid2, NULL);}

输出结果：
in thrFunc1
in thrFunc1
in mutex_init
address: 0x100300070
address: 0x100300070

饿汉模式：

#include <stdio.h>#include <pthread.h>class Singleton{public:    static Singleton* getInstance();protected:    Singleton() {};    static Singleton *_instance;};Singleton* Singleton::_instance = new Singleton();Singleton* Singleton::getInstance(){    return _instance;}void* thrFunc1(void *arg){    auto p = Singleton::getInstance();    printf("address: %p\n", p);    return NULL;}int main(){    pthread_t pid1, pid2;    pthread_create(&pid1, NULL, thrFunc1, NULL);    pthread_create(&pid2, NULL, thrFunc1, NULL);    pthread_join(pid1, NULL);    pthread_join(pid2, NULL);}

输出结果：
address: 0x1003002e0
address: 0x1003002e0

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