Question

我有这个程序：

#include <stdio.h>
#niclude ......

struct sort {
    char  * array;
    int left,right;
};

void quicksortthread(struct sort *s){
    int left, right;
    int i, j, x, tmp;
    pthread_t *th1, *th2;
    char * v;
    struct sort s1;
    struct sort s2;

    left = s->left;
    right = s->right;

    v = s->array;

    printf("\n\n\n\n QT: l=%i, r=%i \n",left,right);

    //sorting algorithm
    if (left >= right)
        return;
    x = v[left];
    i = left - 1;
    j = right + 1;
    while (i < j) {
        while (v[--j] > x);
        while (v[++i] < x);
        if (i < j) {
            char temp = v[i];
            v[i] = v[j];
            v[j] = temp;
        }
    }

    s1.array = v;
    s1.left = left;
    s1.right = j;
    s2.array = v;
    s2.left = j+1;
    s2.right = right;
    printf("1)left = %i; right= %i\n", left,j);
    printf("2)left = %i; right= %i\n", j+1,right);
    pthread_create(&th1, NULL, quicksortthread,&s1);
    pthread_create(&th2, NULL, quicksortthread,&s2);
}

int main (int argc, char ** argv){

    pthread_t *th1;
    int fd, len, pg, i, j;
    int left, right;
    struct stat stat_buf;
    char c, *paddr;
    struct sort s;

    /*..LOTS OF THIGS

      Define right and left as integers and
      paddr as a char *

      ..*/

    if(   (right)   >=  (atoi(argv[2]))  ){

        //printf("filling structure\n");
        s.array = paddr;
        s.left = left;
        s.right = right;
        //printf("creating threads\n");
        pthread_create(&th1, NULL, quicksortthread,&s);
    }

    sleep(100);
}

两次线程调用后，它停止工作。这是因为在函数pthread_create中传递的结构作为最后一个参数，似乎是不正确的。它编译并执行而没有（例如）分段错误。我确信我正在以正确的方式使用结构和指针。

然后程序以这种方式返回：

left = 0; right= 2048
QT: l=0, r=2048 
1)left = 0; right= 0
2)left = 1; right= 2048    

left = 0; right= 0
QT: l=0, r=0 

left = 1037061890; right= 32542
QT: l=1037061890, r=32542

已解决：我已解决此问题以这种方式更改线程例程：

nt left, right;
int i, j, x, tmp;
pthread_t th1, th2;
char * v;
struct sort * s1;
s1= malloc(sizeof(struct sort *));
struct sort * s2;
s2= malloc(sizeof(struct sort *));

left =  s->left;
right = s->right;
printf("\n\n\n\nleft = %i; right= %i\n", left,right);
v =  s->array;
printf("QT: l=%i, r=%i \n",left,right);

if (left >= right)
return;
x = v[left];
i = left - 1;
j = right + 1;
while (i < j) {
while (v[--j] > x);
while (v[++i] < x);
if (i < j) {

   char temp = v[i];
   v[i] = v[j];
   v[j] = temp;
     }
 }

 s1->array = v;
 s1->left = left;
 s1->right = j;
 s2->array = v;
 s2->left = j+1;
 s2->right = right;
 printf("1)left = %i; right= %i\n", left,j);
 printf("2)left = %i; right= %i\n", j+1,right);
 pthread_create(&th1, NULL, quicksortthread,s1);
 pthread_create(&th2, NULL, quicksortthread,s2);

Answer 1

struct sort s是一个自动变量，你将它的指针传递给线程。这不是一个好习惯。即使在调用pthread_create的函数返回后，该线程也会存在，在这种情况下，堆栈变量将超出范围。从quicksortthread函数本身创建线程的方式存在同样的问题，其中struct sort s1和struct sort s2是quicksortthread函数的局部变量。最好动态地为这些结构分配内存。

此外，还不清楚为什么在主要内容中添加了sleep(100)。在退出main之前，您应该使用pthread_join等待创建的线程完成。

pthread_create只需要pthread_t *作为第一个参数，但是，您传递的是pthread**。 pthread_t *th1应为pthread_t th1。

c中的struct指针不返回正确的值

1 个答案: