Question

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

终端上的错误如下......

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

'用于指定字符，"指定字符串。在
```
memset(name, 'no' , sizeof(name));
```
您正在尝试定义c。

'no'

memset用于设置一个内存块一个字符值。您可能需要memcpy或strcpy来初始化名称。
char name[10];定义了一个字符数组，但是如果你想要定义一个字符串数组，则需要char name[10][NAME_LEN];代替（对于字符长度的最大值）。这也应该解决strcpy错误（不要使用＆符号）。
在myfunc1中，您正在取消引用某个角色。将其固定到c字符串的数组将有所帮助，但您不需要取消引用它来打印它。

Answer 2

看起来你在字符串和字符常量之间很困惑。

char name [100]; char c;

字符串始终以“双引号”表示。 A（单个字符）用单引号括起来。所以，“stackoverflow”是一个字符串，'s'，'t'，'a'，'c'，'k'是字符。

此外，从字符串变量中，使用[]运算符提取单个字符，如下所示。请注意，我不使用'*'运算符。

char name[10] ;
char c;
strcpy (name,"stackoverflow");
printf ("name is %s",name);
print ("first character of name is %c", name[0]);

如何从不同的线程访问数组？

2 个答案: