Re: Problem w/ c++,threads,static initializers

[Thomas Pfaff <tpfaff at gmx dot net>]

Rasmus Hahn wrote:
> Hi Thomas,
>
> Problem solved: it was not the mutex but the but the pthread_mutexattr_t
> that caused the error. cygwin's pthread_mutexattr_init () function checks
> if its argument points to a valid object. If the pthread_mutexattr_t's 
> value still points to a valid object (from a previous call)
> pthread_mutexattr_init () fails, and so do later pthread_mutex_init()s with
> this attribute. I think this behaviour is not correct since an uninitialized
> pthread_mutexattr_t can point to anything (as a previously created attribute),
> so this is probably a bug in cygwin (or what does the International Pthread
> Attributes Committee say?). A quick look in winsup/cygwin/thread.cc shows
> that this kind of check is done for more of the ..._init() functions, so there
> may be similar effects (but i did not test that yet). Demo-Program below does
> not work with (my) cygwin but does in my linux box:
>
> #include <pthread.h>
> int main () {
>   pthread_mutexattr_t attr;
>   pthread_mutexattr_init (&attr);
>   if (pthread_mutexattr_init (&attr)) {
>     printf ("error should not happen\n");
>   }
> }

Have a look at
http://www.opengroup.org/onlinepubs/007904975/functions/pthread_mutexattr_init.html 


"Results are undefined if pthread_mutexattr_init() is called specifying 
an already initialized attr attributes object."

Unfortunately the spec does not specify EBUSY (which as returned at the 
moment) as a valid return code for pthread_mutexattr_init, therefore i 
will change all attr_init functions to simply return 0 if they are 
called with an already initialized attribute.

Thomas


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