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Top Forums Programming A weird problem with POSIX function Post 302555894 by bus147 on Friday 16th of September 2011 04:35:51 AM
Old 09-16-2011
A weird problem with POSIX function

Hi all,

Sorry for the title because I didn't find a proper name for it. My question is about POSIX functions, such as timer_create(), mq_open() and pthread_create().

Code:
void test_queue()
{
struct mq_attr attr;

attr.mq_maxmsg = 10;
attr.mq_msgsize = 64;

mq_unlink("/my_test_queue");
if(mq_open("/my_test_queue", (O_RDWR + O_CREATE + O_EXCL), 0777, &attr) == -1)
{
  printf("\n__%s__errno(%d: %s)", __FUNCTION__, errno, strerror(errno));
  return FAIL;
}
}

If I put the above function in main.c, there will have no problem. The queue is successfully created. But if I put in a file, let say foo.c. This file is compiled into libFOO.a and linked with main.c. Then I got the following error: errno(2: No such file or directory)

The other POSIX functions are also same if put in libFOO.a, for example, timer_create() failed with "Invalid argument" errro, pthread_create() succeeds but it is never run.

Is there any difference between running in main.c and foo.c? If you ever experienced such problem then please give me some hints

Thank you very much
 

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PTHREAD_CREATE(3)					   BSD Library Functions Manual 					 PTHREAD_CREATE(3)

NAME
pthread_create -- create a new thread LIBRARY
POSIX Threads Library (libpthread, -lpthread) SYNOPSIS
#include <pthread.h> int pthread_create(pthread_t * restrict thread, const pthread_attr_t * restrict attr, void *(*start_routine)(void *), void * restrict arg); DESCRIPTION
The pthread_create() function is used to create a new thread, with attributes specified by attr, within a process. If attr is NULL, the default attributes are used. The attributes specified via attr are copied into the new thread. Any subsequent modifications to the attributes object attr points to will have no effect upon already-created threads. It is thus also safe to pass the same attr to multiple calls to pthread_create(). Upon successful completion pthread_create() will store the ID of the created thread in the location specified by thread. The thread is cre- ated executing start_routine with arg as its sole argument. If the start_routine returns, the effect is as if there was an implicit call to pthread_exit() using the return value of start_routine as the exit status. Note that the thread in which main() was originally invoked differs from this. When it returns from main(), the effect is as if there was an implicit call to exit() using the return value of main() as the exit status. The signal state of the new thread is initialized as: o The signal mask is inherited from the creating thread. o The set of signals pending for the new thread is empty. RETURN VALUES
If successful, the pthread_create() function will return zero. Otherwise an error number will be returned to indicate the error. ERRORS
pthread_create() shall fail if: [EAGAIN] The system lacks the necessary resources to create another thread, or the system-imposed limit on the total number of threads in a process PTHREAD_THREADS_MAX would be exceeded. [EINVAL] The value specified by attr is invalid. SEE ALSO
fork(2), pthread_attr(3), pthread_cleanup_pop(3), pthread_cleanup_push(3), pthread_exit(3), pthread_join(3) STANDARDS
The function conforms to IEEE Std 1003.1-2001 (``POSIX.1''). BSD
July 9, 2010 BSD
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