Question

我从Linux pthread pdf文件中复制此代码。这段代码描述了客户和生产者的问题，演示使用链表来实现这个模型。当我通过gcc编译时，显示此错误，我该如何解决？我尝试修改if（ - ＆gt; if（）或pthread_mutex_lock（＆amp; mtx）; - ＆gt; pthread_mutex_lock（＆amp; mtx））;在36行之前添加或删除}，但不起作用。

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Answer 1

您的代码存在很多问题。您需要了解编译器报告的内容，否则修复代码并不容易。我建议你从学习C的基础知识开始。

来自GCC编译器的错误：

xx.c: In function ‘thread_func’:
xx.c:28:29: error: expected ‘)’ before ‘;’ token
     pthread_mutex_lock(&mtx);
                             ^
xx.c:36:5: error: expected expression before ‘}’ token
     }
     ^
xx.c: In function ‘main’:
xx.c:53:1: error: unknown type name ‘be’
 be add lock/mutex
 ^
xx.c:53:8: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘lock’
 be add lock/mutex
        ^

很容易理解错误并解决问题。我建议你开始学习如何调试你的程序。

其他语法错误
该标志不是由任何人设置的，该变量的使用是徒劳的。我刚把它删除了。

了解pthreads的一些有用链接：

Pthreads examples.
Understanding GCC compiler error and warnings。

更正后的代码

在下面的代码中，我刚刚更正了编译器错误并删除了未使用的变量以便工作。

我从您的问题中学到了什么，您使用了Linux书籍示例，在编辑器中复制并运行，并且您最终遇到了问题，所以我建议您学习基本的C语法并理解GCC警告和错误。< / p>

#include <pthread.h>
#include <unistd.h>
#include <stdio.h>
#include <malloc.h>

static pthread_mutex_t mtx = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;

struct node {
    int n_number;
    struct node *n_next;
} *head = NULL;

static void cleanup_handler(void *arg)
{
    printf("Cleanup handler of second thread\n");
    free(arg);
    pthread_mutex_unlock(&mtx);
}

static void *thread_func(void *arg)   // customer
{
    struct node *p = NULL;

    pthread_cleanup_push(cleanup_handler, p);
    while (1)
    {
    pthread_mutex_lock(&mtx);
    while (head == NULL){
      pthread_cond_wait(&cond,&mtx);
    }
    p = head;
    head = head->n_next;
    printf("Got %d from front of queue\n", p->n_number);
    free(p);
    pthread_mutex_unlock(&mtx);
    }

    pthread_exit(NULL);
    pthread_cleanup_pop(0); // must be put in last line
}

int main(void)
{
    pthread_t tid;
    int i;
    struct node *p;
    pthread_create(&tid, NULL, thread_func, NULL);
    for (i = 0; i < 10; i++)  // producer
    {
    p = (struct node*)malloc(sizeof(struct node));
    p->n_number = i;
    // because head is share，visit share data must be add lock/mutex
    pthread_mutex_lock(&mtx);
    p->n_next = head;
    head = p;
    pthread_cond_signal(&cond);
    pthread_mutex_unlock(&mtx);
    sleep(1);
    }
    printf("thread 1 wanna end the line.So cancel thread 2.\n");
    pthread_cancel(tid);
    pthread_join(tid, NULL);
    printf("All done------exiting\n");
    return 0;
}

Answer 2

来自word文件的Corrent代码。书中的PDF代码是培训机构数据，我认为员工/教师编辑错误。

#include <pthread.h> 
#include <unistd.h>
#include <stdio.h>
#include <malloc.h>    // 1.work on Linux  
                       // 2. error on OS X,fatal error:'malloc.h' file not 
                       //   found #include <malloc.h> ^~~~~~~~~~1 error 
                       // generated.

#include <stdlib.h>    // work on OS X      

static pthread_mutex_t mtx = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
struct node {
        int n_number;
        struct node *n_next;
} *head = NULL;

static void cleanup_handler(void *arg)
{
    printf("Cleanup handler of second thread\n");
    free(arg);
    pthread_mutex_unlock(&mtx);
}

static void *thread_func(void *arg)// customer
{
    struct node *p = NULL;
    pthread_cleanup_push(cleanup_handler, p);
    while (1)
    {
        pthread_mutex_lock(&mtx);
        while (head == NULL){ 
            pthread_cond_wait(&cond,&mtx);
      }
        p = head;
        head = head->n_next;
        printf("Got %d from front of queue\n", p->n_number);
        free(p);
        pthread_mutex_unlock(&mtx);
    }
    pthread_exit(NULL);
    pthread_cleanup_pop(0);   //must be put in last line 
}
int main(void)
{
    pthread_t tid;
    int i;
    struct node *p;
    pthread_create(&tid, NULL, thread_func, NULL);
    for (i = 0; i < 10; i++) // producer
    {
            p = (struct node*)malloc(sizeof(struct node));
            p->n_number = i;
            pthread_mutex_lock(&mtx);// because head is share，visit share data
                                     // must be add lock/muck
            p->n_next = head;
            head = p;
            pthread_cond_signal(&cond);
            pthread_mutex_unlock(&mtx);
            sleep(1);
    }
    printf("thread 1 wanna end the line.So cancel thread 2.\n");
    pthread_cancel(tid);
    pthread_join(tid, NULL);
    printf("All done------exiting\n");
    return 0;
}

gcc编译期望'）'之前';'标记，错误：预期表达式在'}'标记之前}

2 个答案: