pthread_mutex_t的源码求助，类型的定义的问题

[iceeajp]

今天在看pthread_mutex_init的源码的时候，发现pthread_mutex_t 的使用出现了我不可理解的两种不同的定义。
追踪pthread.h里面 pthread_mutex_t的定义，在_types.h里找到的如下:

struct _opaque_pthread_mutex_t { long __sig; char __opaque[__PTHREAD_MUTEX_SIZE__]; };

但是在pthread_mutex_init函数中却使用了 pthread_mutex_t mx; mx->lock_idx ,
代码中把 pthread_mutex_t 当做指针来使用了。。
这是为什么呢？？求各位大神指导。

pthread_mutex_init的实现代码如下:

#include "pthread.h"
#include "implement.h"


int
pthread_mutex_init (pthread_mutex_t * mutex, const pthread_mutexattr_t * attr)
{
  int result = 0;
  pthread_mutex_t mx;

  if (mutex == NULL)
    {
      return EINVAL;
    }

  if (attr != NULL
      && *attr != NULL && (*attr)->pshared == PTHREAD_PROCESS_SHARED)
    {
      /**
       * Creating mutex that can be shared between
       * processes.
       */
#if _POSIX_THREAD_PROCESS_SHARED >= 0

      /**
       * Not implemented yet.
       */

#error ERROR [__FILE__, line __LINE__]: Process shared mutexes are not supported yet.

#else

      return ENOSYS;

#endif /** _POSIX_THREAD_PROCESS_SHARED */

    }

  mx = (pthread_mutex_t) calloc (1, sizeof (*mx));

  if (mx == NULL)
    {
      result = ENOMEM;
    }
  else
    {
      mx->lock_idx = 0;
      mx->recursive_count = 0;
      mx->kind = (attr == NULL || *attr == NULL
		  ? PTHREAD_MUTEX_DEFAULT : (*attr)->kind);
      mx->ownerThread.p = NULL;

      mx->event = CreateEvent (NULL, PTW32_FALSE,    /** manual reset = No */
                              PTW32_FALSE,           /** initial state = not signaled */
                              NULL);                 /** event name */

      if (0 == mx->event)
        {
          result = ENOSPC;
          free (mx);
          mx = NULL;
        }
    }

  *mutex = mx;

  return (result);
}

[空的]

我的VM里 pthread_mutex_t 定义在. bits/pthreadtypes.h

typedef union
{
  struct __pthread_mutex_s
  {
    int __lock;
    unsigned int __count;
    int __owner;
#if __WORDSIZE == 64
    unsigned int __nusers;
#endif
    /* KIND must stay at this position in the structure to maintain
       binary compatibility.  */
    int __kind;
#if __WORDSIZE == 64
    int __spins;
    __pthread_list_t __list;
# define __PTHREAD_MUTEX_HAVE_PREV      1
#else
    unsigned int __nusers;
    __extension__ union
    {
      int __spins;
      __pthread_slist_t __list;
    };
#endif
  } __data;
  char __size[__SIZEOF_PTHREAD_MUTEX_T];
  long int __align;
} pthread_mutex_t;

确定代码实现和头文件是同一系统的么？

[iceeajp]

引用 1 楼 erhou134 的回复:

我的VM里 pthread_mutex_t 定义在. bits/pthreadtypes.h

typedef union
{
  struct __pthread_mutex_s
  {
    int __lock;
    unsigned int __count;
    int __owner;
#if __WORDSIZE == 64
    unsigned int __nusers;
#endif
    /* KIND must stay at this position in the structure to maintain
       binary compatibility.  */
    int __kind;
#if __WORDSIZE == 64
    int __spins;
    __pthread_list_t __list;
# define __PTHREAD_MUTEX_HAVE_PREV      1
#else
    unsigned int __nusers;
    __extension__ union
    {
      int __spins;
      __pthread_slist_t __list;
    };
#endif
  } __data;
  char __size[__SIZEOF_PTHREAD_MUTEX_T];
  long int __align;
} pthread_mutex_t;

确定代码实现和头文件是同一系统的么？

我的是在mac下面的。我也怀疑是不一致。。谢谢你的帮助