c - 创建用户输入的多个线程时出现段错误

Question

我正在尝试使用 pthreads 和 vector 形式的缓冲区来解决生产者-消费者问题。我希望能够输入生产者和消费者的线程数量。一旦我输入这两个值，我就会遇到段错误。我正在使用 gcc 和 -lpthread 编译代码，但没有收到编译错误。如何修复此错误？

#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>

#define MAX 1000//00            /* Numbers to produce */
#define SIZE 20                 /* Size of Buffer     */

typedef struct {
    int id;
} parm;

pthread_mutex_t the_mutex;
pthread_cond_t condc, condp;
int buffer[SIZE];
int c = 0;

/* 
    @Function: printState
    @In: integer i
    @Out: none

    @Description: Used to show the state of the buffer on a given state
*/
void printState(int i){
    int j;

    puts("Showing the state of the buffer: ");
    printf("[ ");
    for (j = 0; j < SIZE; j++){
        printf("%d ",buffer[j]);
    }
    printf("]\n");

}

/*
    @Function: producer
    @In: void *ptr
    @Out: none

    @Description: Call a producer on the process
*/

void* producer(void *ptr){
    int i;

    for (i = 1; i <= MAX; i++){
        printf("calling producer\n");// on position %d.\n",c+1);
        pthread_mutex_lock(&the_mutex); /* protect the buffer */

        if(c == SIZE){  /* If the buffer is full, wait */
            puts("The buffer is full. Waiting.");
            pthread_cond_wait(&condp, &the_mutex);
        }

        buffer[c] = 1;
        c++;

        printf("There are %d occupied positions on the buffer.\n", c);
        pthread_cond_signal(&condc); /* Wake up the consumer */
        pthread_mutex_unlock(&the_mutex); /* Release the buffer */

        //if(i == MAX/2){
        //  printState(i);
        //}

    }
    pthread_exit(0);
}

/*
    @Function: consumer
    @In: void *ptr
    @Out: none

    @Description: Call a consumer on the process
*/
void* consumer(void *ptr) {
    int i, j;

    for (i = 1; i <= MAX; i++){ 
        printf("calling consumer\n");// on position %d\n", c+1);    
        pthread_mutex_lock(&the_mutex); /* protect the buffer */
        if (c == 0){ /* If there is nothing in the buffer, wait */
            puts("Buffer is empty. Waiting.");
            pthread_cond_wait(&condc, &the_mutex);
        }
        buffer[c] = 0;
        c--;
        printf("There are %d occupied positions on the buffer.\n", c);

        pthread_cond_signal(&condp); /* wake up consumer */
        pthread_mutex_unlock(&the_mutex); /* release the buffer */

        //if(i == MAX){
        //  printState(i);
        //}

    }
    pthread_exit(0);
}

/*
    @Function: main
    @In: integer argc and character **argv
    @Out: none

    @Description: Main function of the algorithm
*/
int main(int argc, char **argv){
    pthread_t *pro_threads, *con_threads;
    pthread_attr_t pro_pthread_custom_attr, con_pthread_custom_attr;
    int i, M, N;
    parm *p_pro, *p_con;

    puts("Please, enter the number of producer threads:");
    scanf("%d",&N);

    puts("Please, enter the number of consumer threads:");
    scanf("%d",&M);

    for(i=0;i<SIZE;i++){
        buffer[i] = 0;
    } 

    // Allocate space for the threads

    pro_threads=(pthread_t *)malloc(N*sizeof(*pro_threads));
    pthread_attr_init(&pro_pthread_custom_attr);
    con_threads=(pthread_t *)malloc(M*sizeof(*con_threads));
    pthread_attr_init(&con_pthread_custom_attr);

    // Initialize the mutex and condition variables

    pthread_mutex_init(&the_mutex, NULL); /* Initialize the mutex */
    pthread_cond_init(&condc, NULL); /* Initialize the consumer condition variable */
    pthread_cond_init(&condp, NULL); /* Initialize the producer condition variable */

    // Create the threads

    for (i=0; i<N; i++){
        p_pro[i].id=i;
        pthread_create(&pro_threads[i], &pro_pthread_custom_attr, producer, (void *)(p_pro+i));
    }

    for (i=0; i<M; i++){
        p_con[i].id=i;
        pthread_create(&con_threads[i], &con_pthread_custom_attr, consumer, (void *)(p_con+i));
    }

    // Wait for the threads to finish.
    // Otherwise main might run to the end
    // and kill the entire process when it exits.

    for (i=0; i<N; i++){

        pthread_join(pro_threads[i], NULL);
    }

    for (i=0; i<M; i++){

        pthread_join(con_threads[i], NULL);
    }

    // Cleanup -- would happen automatically at the end of program

    pthread_mutex_destroy(&the_mutex); /* Free up the_mutex */
    pthread_cond_destroy(&condc); /* Free up the consumer condition variable */
    pthread_cond_destroy(&condp); /* Free up the producer condition variable */
    free(p_pro);
    free(p_con);
    return 0;
}

Answer 1

这是大学类(class)还是其他类(class)？

如果您要求编译器 (gcc) 启用警告，该问题就会被报告。无论是谁在“教”你，都应该告诉你这一点。

meh.c: In function ‘printState’: meh.c:25:21: warning: unused parameter ‘i’ [-Wunused-parameter] void printState(int i){ ^ meh.c: In function ‘producer’: meh.c:47:22: warning: unused parameter ‘ptr’ [-Wunused-parameter] void* producer(void ptr){ ^ meh.c: In function ‘consumer’: meh.c:85:12: warning: unused variable ‘j’ [-Wunused-variable] int i, j; ^ meh.c:84:22: warning: unused parameter ‘ptr’ [-Wunused-parameter] void consumer(void *ptr) { ^ meh.c: In function ‘main’: meh.c:118:14: warning: unused parameter ‘argc’ [-Wunused-parameter] int main(int argc, char **argv){ ^ meh.c:118:27: warning: unused parameter ‘argv’ [-Wunused-parameter] int main(int argc, char **argv){ ^ meh.c:150:14: warning: ‘p_pro’ may be used uninitialized in this function [-Wmaybe-uninitialized] p_pro[i].id=i; ^ meh.c:155:14: warning: ‘p_con’ may be used uninitialized in this function [-Wmaybe-uninitialized] p_con[i].id=i;

但是，即使使用标准方法(例如到处放置 printfs 来缩小崩溃站点的范围)，也可以轻松诊断问题。

因此，我很困惑到底出了什么问题。

代码有一些微不足道的错误，即使修复了段错误，它也无法工作。我将省略它们，因为它们处理的是一般问题。

#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>

#define MAX 1000//00            /* Numbers to produce */
#define SIZE 20                 /* Size of Buffer     */

typedef struct {
    int id;
} parm;

pthread_mutex_t the_mutex;
pthread_cond_t condc, condp;
int buffer[SIZE];
int c = 0;

它已经是 0。对于全局变量来说，这是一个糟糕的非描述性名称。 //-------------------------------------------------------- --------------------------------------------

/* @函数:打印状态 @In:整数i @Out:无

    @Description: Used to show the state of the buffer on a given state
*/
void printState(int i){

未使用错误命名的参数。

    int j;

习惯用法是使用“i”作为循环索引。

    puts("Showing the state of the buffer: ");
    printf("[ ");
    for (j = 0; j < SIZE; j++){
        printf("%d ",buffer[j]);
    }
    printf("]\n");

}
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
/*
    @Function: producer
    @In: void *ptr
    @Out: none

    @Description: Call a producer on the process
*/

void* producer(void *ptr){

“*”的位置不一致。将其与类型名称放在一起很糟糕。

    int i;

    for (i = 1; i <= MAX; i++){

'i' 不在循环内使用，因此实际值并不重要。习惯用法是从 0 到 < MAX。

        printf("calling producer\n");// on position %d.\n",c+1);
        pthread_mutex_lock(&the_mutex); /* protect the buffer */

        if(c == SIZE){  /* If the buffer is full, wait */
            puts("The buffer is full. Waiting.");
            pthread_cond_wait(&condp, &the_mutex);
        }

        buffer[c] = 1;
        c++;

        printf("There are %d occupied positions on the buffer.\n", c);
        pthread_cond_signal(&condc); /* Wake up the consumer */
        pthread_mutex_unlock(&the_mutex); /* Release the buffer */

        //if(i == MAX/2){
        //  printState(i);
        //}

    }
    pthread_exit(0);
}
//-----------------------------------------------------------------------------


//-----------------------------------------------------------------------------
/*
    @Function: consumer
    @In: void *ptr
    @Out: none

    @Description: Call a consumer on the process
*/
void* consumer(void *ptr) {
    int i, j;

    for (i = 1; i <= MAX; i++){ 
        printf("calling consumer\n");// on position %d\n", c+1);    
        pthread_mutex_lock(&the_mutex); /* protect the buffer */
        if (c == 0){ /* If there is nothing in the buffer, wait */
            puts("Buffer is empty. Waiting.");
            pthread_cond_wait(&condc, &the_mutex);
        }
        buffer[c] = 0;
        c--;
        printf("There are %d occupied positions on the buffer.\n", c);

        pthread_cond_signal(&condp); /* wake up consumer */
        pthread_mutex_unlock(&the_mutex); /* release the buffer */

        //if(i == MAX){
        //  printState(i);
        //}

    }
    pthread_exit(0);
}
//-----------------------------------------------------------------------------

//-----------------------------------------------------------------------------
/*
    @Function: main
    @In: integer argc and character **argv
    @Out: none

    @Description: Main function of the algorithm
*/
int main(int argc, char **argv){
    pthread_t *pro_threads, *con_threads;
    pthread_attr_t pro_pthread_custom_attr, con_pthread_custom_attr;
    int i, M, N;

全大写的名称通常与宏一起使用。可怕的非描述性名称。

    parm *p_pro, *p_con;

    puts("Please, enter the number of producer threads:");
    scanf("%d",&N);

    puts("Please, enter the number of consumer threads:");
    scanf("%d",&M);

我不知道谁以及为什么建议初学者使用这个。请改用 argv。

    for(i=0;i<SIZE;i++){
        buffer[i] = 0;
    } 

该缓冲区已归零。与之前使用的间距不一致。

    // Allocate space for the threads

    pro_threads=(pthread_t *)malloc(N*sizeof(*pro_threads));

强制转换 malloc 是非常有害的。

    pthread_attr_init(&pro_pthread_custom_attr);
    con_threads=(pthread_t *)malloc(M*sizeof(*con_threads));
    pthread_attr_init(&con_pthread_custom_attr);

    // Initialize the mutex and condition variables

    pthread_mutex_init(&the_mutex, NULL); /* Initialize the mutex */
    pthread_cond_init(&condc, NULL); /* Initialize the consumer condition variable */
    pthread_cond_init(&condp, NULL); /* Initialize the producer condition variable */

    // Create the threads

    for (i=0; i<N; i++){
        p_pro[i].id=i;

p_pro 未初始化。

        pthread_create(&pro_threads[i], &pro_pthread_custom_attr, producer, (void *)(p_pro+i));

缺少错误检查。 p_pro 使用不一致。

    }

    for (i=0; i<M; i++){
        p_con[i].id=i;
        pthread_create(&con_threads[i], &con_pthread_custom_attr, consumer, (void *)(p_con+i));
    }

    // Wait for the threads to finish.
    // Otherwise main might run to the end
    // and kill the entire process when it exits.

    for (i=0; i<N; i++){

        pthread_join(pro_threads[i], NULL);
    }

    for (i=0; i<M; i++){

        pthread_join(con_threads[i], NULL);
    }

    // Cleanup -- would happen automatically at the end of program

    pthread_mutex_destroy(&the_mutex); /* Free up the_mutex */
    pthread_cond_destroy(&condc); /* Free up the consumer condition variable */
    pthread_cond_destroy(&condp); /* Free up the producer condition variable */
    free(p_pro);
    free(p_con);
    return 0;
}