Re: Extended attributes and thread safety

On Aug 31, 2009, at 10:06 , Christiaan Hofman wrote:

>
> On Aug 31, 2009, at 8:36, Chris Suter wrote:
>
>> Hi Christian,
>>
>> On Sun, Aug 30, 2009 at 9:48 PM, Christiaan  
>> Hofman<[email protected]> wrote:
>>> Does anybody know whether it is safe to use the extended attribute  
>>> C-library
>>> at sys/xattr.h (getxattr, setxattr, etc) on background threads? The
>>> documentation does not mention anything about thread safety, but I  
>>> could
>>> imagine it to run into problems if it'd use global resources, and  
>>> the
>>> functions seem to use at least one global variable.
>>
>> Those functions will be thread safe. It's a bug if they're not.
>>
>> Kind regards,
>>
>> Chris
>
> Thanks Chris. However I am still worried about the fact that they  
> access the global variable errno.

On Mac OS X, errno is a macro wrapping access to a thread-safe variable:

extern int * __error(void);
#define errno (*__error())

Cheers,
Graham.