__USE_GNU的问题

最新推荐文章于 2023-05-31 17:20:47 发布

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最新推荐文章于 2023-05-31 17:20:47 发布

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在尝试编译包含PTHREAD_MUTEX_ROBUST_NP的C程序时，遇到了未定义的错误。检查pthread.h头文件后，发现在`__USE_GNU`预处理器指令下定义了相关枚举。尝试添加-D__USE_GNU编译选项，但问题依旧存在。搜索解决方案中。

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程序示例：

。。。

头文件和其他函数及全局变量

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

  int i=0;

  if(argc == 2)
   i = atoi(argv[1]);

  getseg(&g_data);

  pthread_mutexattr_t mutex_shared_attr;

  /* Set pthread_mutex_attr to process shared */
  pthread_mutexattr_init(&mutex_shared_attr);
  pthread_mutexattr_setpshared(&mutex_shared_attr, PTHREAD_PROCESS_SHARED);
  pthread_mutexattr_setrobust_np(&mutex_shared_attr, PTHREAD_MUTEX_ROBUST_NP);

  pthread_mutex_init(&g_data->sum_mutex, &mutex_shared_attr);

  process_fn(i);

  printf("%u in the end, the shared sum: %d\n",getpid(), g_data->counter);
  return 0;
}

[root@Cross-Main threading]# gcc shm_lock.c -o shm_lock -lpthread
shm_lock.c: In function ‘main’:
shm_lock.c:93: error: ‘PTHREAD_MUTEX_ROBUST_NP’ undeclared (first use in this function)
shm_lock.c:93: error: (Each undeclared identifier is reported only once
shm_lock.c:93: error: for each function it appears in.)

编译时出现PTHREAD_MUTEX_ROBUST_NP未定义的问题

在pthread.h中发现

#ifdef __USE_GNU
/* Robust mutex or not flags. */
enum
{
PTHREAD_MUTEX_STALLED_NP,
PTHREAD_MUTEX_ROBUST_NP
};
#endif

修改编译选项依然编译不过

[root@Cross-Main threading]# gcc shm_lock.c -o shm_lock -lpthread -D__USE_GNU
shm_lock.c: In function ‘main’:
shm_lock.c:93: error: ‘PTHREAD_MUTEX_ROBUST_NP’ undeclared (first use in this function)
shm_lock.c:93: error: (Each undeclared identifier is reported only once
shm_lock.c:93: error: for each function it appears in.)

百度一下查到解决方案：

This is wrong, __USE_GNU is glibc internal macro that shouldn't be ever
defined by apps.
The way to select GNU feature set in glibc headers is to define _GNU_SOURCE,
either before including first include header in the source .c/.C file,
or by defining it on the command line (-D_GNU_SOURCE).

[root@Cross-Main threading]# gcc shm_lock.c -o shm_lock -lpthread -D_GNU_SOURCE
[root@Cross-Main threading]#