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Old 10-29-2007, 08:23 AM   #1
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Question return code or errno?

Here is a snippet from the pthread_mutex_lock() man page

RETURN VALUE If successful, the pthread_mutex_lock() and pthread_mutex_unlock() functions return zero. Otherwise, an error number is returned to indicate the error.

Following it is a list of possible error codes, EINVAL, EBUSY, etc.

Does the help mean that one of the error codes is returned as the return code of pthread_mutex_lock() or that pthread_mutex_lock() returns non-zero (meaning what?) and sets errno to one of the error codes?


Old 10-29-2007, 08:45 AM   #2
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The call will return the error code, or zero on success.

errno is defined in the ISO standard C library, and (if memory serves), can only be modified by certain standard function calls. Since pthread is not a part of standard C (nor is any kind of threading support), pthread should not be modifying errno.


—Robert J Lee
Old 10-29-2007, 09:23 AM   #3
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Interestingly enough, the compiler does not complain if you write:

errno = 3;

And that "other' operating system has SetLastError() and assigns a group of error numbers to be locally administerd.

But I understand your post and that makes much sense.





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