Question

#include  pthread.h
#include stdio.h

static int seq[50];
void *runner(void *); /* the thread */

int main(int argc, char *argv[])
{
    int y;
    pthread_t tid[3]; /* the thread identifier */
    pthread_attr_t attr; /* set of attributes for the thread */
    if(argc!=2)
    {
        fprintf(stderr,"you need to enter two arguments");
        exit(-1);
    }
    else
    {
        int a = atoi(argv[1]);
        if(a>0)
        {
            y=a;
        }
        else
        {
            fprintf(stderr,"you need to enter a valid number greater than zero");
            exit(-1);
        }
    }
    /* get the default attributes */
    pthread_attr_init(&attr);
    pthread_attr_setdetachstate(&attr,PTHREAD_CREATE_DETACHED);
    /* create three threads */
    pthread_create(&tid, NULL, runner,(void *)y);
    /* now wait for the thread to exit */
    sleep(2);
    printf( " Am in main process, The sequence is  ");
    int j=0,val=0;
    for( j = 0; j < 40; j++)
    {
        val=seq[j];
        if(val>=1)
            printf( "  %d  ", seq[j]);
    }
    pthread_join(tid, NULL);
    pthread_exit(0);
}
/**
 * The thread will begin control in this function
 */
void *runner(void *param)
{
    int count=0;
    int y= (int *) param;
    //       printf(" Am in runner");
    while(y!=1)
    {
        if(y%2==0)
            y = y/2;
        else
            y= ((3*y)+1);
        //  printf(" %d ", y);
        seq[count] = y;
        count++;

    }
    pthread_exit(0);
}

我收到以下错误

bonus.c: In function ‘main’:
bonus.c:91: warning: cast to pointer from integer of different size
bonus.c:91: warning: passing argument 1 of ‘pthread_create’ from incompatible pointer type
bonus.c:123: warning: passing argument 1 of ‘pthread_join’ makes integer from pointer without a cast
bonus.c: In function ‘runner’:
bonus.c:157: warning: comparison between pointer and integer
bonus.c:159: error: invalid operands to binary %
bonus.c:161: error: invalid operands to binary /
bonus.c:165: error: invalid operands to binary *
bonus.c:171: warning: assignment makes integer from pointer without a cast

Answer 1

无论出于何种原因，您都要声明一组pthread_t：

pthread_t tid[3];

除非你计划开始三个主题，否则不要这样做你想要

pthread_t tid;

两个错误源于此：

pthread_create(&tid, NULL, runner,(void *)y);
(passing argument 1 of ‘pthread_create’ from incompatible pointer type)

您传递指向数组的指针而不是指向pthread_t和

的指针

pthread_join(tid, NULL);
(passing argument 1 of ‘pthread_join’ makes integer from pointer without a cast)

您将指针传递给pthread_t而不是pthread_t。

警告

cast to pointer from integer of different size

来自(void*) y - 如果您正在为64位目标进行编译，则int小于void*。
您应该使用&y或为y提供与void*一样大的类型，例如int64_t。

在runner中，您将参数转换为int*，这是非常奇怪的，因为它最初是int。
您需要确保退回到与之相同的类型然后，您可以使用此值初始化int，但这可能不是您的实际代码，因为以下错误与

一致

int* y = (int *) param;

所以我怀疑你输了＃34; *＆＃34;输入问题中的代码时。

如果您在参数中传递指向int的指针，则应为

int y = *(int*) param;

如果传递一个重新解释为指针的整数，它应该是

int64_t y = (int64_t) param;

如果您确定int64_t作为整数类型。

另外，请记住，在线程修改它们时打印数组元素可能不是最好的想法，也不能确保线程不会超出数组边界。

Answer 2

pthread_create(&tid, NULL, runner,(void *)y);

==＆GT;

for( i = 0; i < 3; i++){
    pthread_create(&tid[i], NULL, runner,(void *)y);
}

和

pthread_join(tid, NULL);

==＆GT;

for( i = 0; i < 3; i++){
    pthread_join(tid[i], NULL);
}

警告：传递'pthread_join'的参数1会从指针生成整数，而不会出现强制转换错误

2 个答案: