c - 如何从不同的线程访问数组？

Question

我是 C 语言的新手。我知道线程是如何工作的，但我认为我仍然不明白指针如何与 char 数组一起工作，如何使用循环填充数组...

终端报错如下...

q2.c: In function ‘main’:
q2.c:18:22: warning: multi-character character constant [-Wmultichar]
q2.c:23:57: warning: multi-character character constant [-Wmultichar]
q2.c:23:40: warning: passing argument 2 of ‘strcpy’ makes pointer from integer without a cast [enabled by default]
In file included from q2.c:4:0:
/usr/include/string.h:128:14: note: expected ‘const char * __restrict__’ but argument is of type ‘int’
q2.c: In function ‘myfunc1’:
q2.c:61:23: error: invalid type argument of unary ‘*’ (have ‘int’)
ubuntu@ubuntu-VirtualBox:~/Desktop$ gcc q2.c -lpthread -o hell
q2.c: In function ‘main’:
q2.c:18:22: warning: multi-character character constant [-Wmultichar]
q2.c:23:57: warning: multi-character character constant [-Wmultichar]
q2.c:23:40: warning: passing argument 2 of ‘strcpy’ makes pointer from integer without a cast [enabled by default]
In file included from q2.c:4:0:
/usr/include/string.h:128:14: note: expected ‘const char * __restrict__’ but argument is of type ‘int’
q2.c: In function ‘myfunc1’:
q2.c:61:23: error: invalid type argument of unary ‘*’ (have ‘int’)

代码:

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

void *myfunc1(void *ptr);
void *myfunc2(void *ptr);

pthread_mutex_t lock;
char name[10];
int id[10];
int i;

int main (int argc, char argv[])
{


        memset(name, 'no' , sizeof(name));
        memset(id, 0, sizeof(id));
        for(i=0; i<10; i++)
                {

                                       strcpy(&name[i], 'name');

                    id[i] = i;
                }
                                //name[10] = '\0';

        pthread_t thrd1, thrd2;
        int thret1, thret2;
        char *msg1 = "First Thread";
        char *msg2 = "Second Thread";



                thret2 = pthread_create(&thrd2, NULL, myfunc2, (void *)msg2);
        thret1 = pthread_create(&thrd1, NULL, myfunc1, (void *)msg1);


        pthread_join(thrd1, NULL);
        pthread_join(thrd2, NULL);

        printf("\nthret1 = %d\n", thret1);
        printf("\nthret2 = %d\n", thret2);
        sleep(5);
        printf("Parent Thread exiting...\n");
        exit(1);

        return 0;
}

void *myfunc1(void *ptr){

        int i;
        char *msg = (char *)ptr;
        printf("\nMsg : %s\n", msg);

        pthread_mutex_lock(&lock);
            for(i=0; i<10; i++)
                {
                    printf("\n %s ", *name[i]);

                }

        pthread_mutex_unlock(&lock);
}

void *myfunc2(void *ptr){

        int i;
        char *msg = (char *)ptr;
        printf("Msg : %s\n", msg);

        pthread_mutex_lock(&lock);
                for(i=0; i<10; i++)
                {

                    printf("\n%d ", id[i]);
                }
        pthread_mutex_unlock(&lock);
}

Answer 1

1. '是指定字符，"是指定字符串。在

   memset(name, 'no' , sizeof(name));
   

   您正在尝试定义 c 中不允许的 'no'。

2. memset 用于设置一 block 内存的一个字符值。您可能需要 memcpy 或 strcpy 来初始化名称。

3. char name[10]; 定义了一个字符数组，但是如果你想定义一个字符串数组，你需要 char name[10][NAME_LEN ]; 而不是(对于字符长度的任何最大值)。这也应该修复 strcpy 错误(不要使用 & 符号)。

4. 在 myfunc1 中，您正在取消引用一个字符。将其固定为 C 字符串的数组会有所帮助，但您无需取消引用它即可打印它。