将结构作为void指针传递给函数

Question

我正在尝试将结构的指针传递给函数,但是当我尝试访问结构时,结构中的最后一个变量丢失了1个字节的内存地址,从而导致使用该变量进行段错误.

typedef struct
{
  pthread_t tID;
  int tType;
}sThread;

sThread threads[MAX_THREADS];

typedef struct
{
  int tID;
  int sock;
  int arg_count;
  char *from_p, **arg_p;
}command_struct;

pthread_t Thread_Start(void *function, void *param)
{
  pthread_t tHandle;

  pthread_create(&tHandle, NULL, function, (void*)param);

  return tHandle;
}

void cmd_test(int sock, char *from_p, char **arg_p, int arg_count)
{ 
  if(thread_check(1))
  {
    send_line(sock, "%s :test thread already running", from_p);
    return;
  }

  command_struct test;

  test.tID = thread_add(1);
  test.arg_count = arg_count;
  test.arg_p = arg_p;

  threads[test.tID].tID = Thread_Start(test_cmd, &test);
}

void *test_cmd(void *param)
{ 
  command_struct test = *((command_struct *)param);

  int i = 0;

  for(i = 1; i < test.arg_count; i++)
  {
    printf("%s", test.arg_p[i]);
  }

  thread_clear(test.tID);
  return NULL;
}

发生的事情是cmd_test(产生线程的函数)内部结构被正确初始化并且所有变量都是正确的.

$1 = {tID = 0, sock = 5, arg_count = 5, from_p = 0xbffff254 "test", arg_p = 0xbfffec48}

但是,如果在运行的线程内部使用test_cmd,则结构缺少arg_p的地址1个字节,导致:

$1 = {tID = 0, sock = 5, arg_count = 5, from_p = 0xbffff254 "test", arg_p = 0xffec48}

如果我在command_struct arg_p的地址末尾添加一个无用的变量然后变得正确,并且command_struct中的最后一个变量缺少1个字节的内存地址.

Answer 1

您将指向局部变量的指针传递给线程 - 当线程访问它时，内存已被重用于其他用途。

尝试这个：

void cmd_test(int sock, char *from_p, char **arg_p, int arg_count)
{ 
    if(thread_check(1))
    {
        send_line(sock, "%s :test thread already running", from_p);
        return;
    }

    // === begin modified code in cmd_test():
    command_struct* test = malloc(sizeof(command_struct));

    test->tID = thread_add(1);
    test->arg_count = arg_count;
    test->arg_p = arg_p;

    threads[test.tID].tID = Thread_Start(test_cmd, test);
    // === end modified code
}

void *test_cmd(void *param)
{ 
    command_struct test = *((command_struct *)param);
    free(param);    // <-- new line of code

    // remainder is the same...
    // ...
}