[boost] Re: thread lib review

From: John Maddock (John_Maddock_at_[hidden])
Date: 2001-09-11 05:37:21

>Coincidence and the happy circumstance that POSIX is very well 
>thought out.  However, I'm not sure I agree with POSIX in this 
>particular case.  Counting semaphores are useful for limiting access 
>to a resource to a specified number of threads.  With out being able 
>to set a maximum value it's very possible to accidently increment the 
>semaphore value more times then you should have, resulting in an 
>error whereby too many threads are allowed access.  Defining the 
>maximum shouldn't be a terribly burdensome requirement on the 
>implementation, and it definately illiminates some sources of error.

OK.

>I've seen several "portable" threading libraries that seem unaware of 
>this.  Like I said, I'm not a POSIX expert.  If someone can replace 
>the hard coded definitions with POSIX sanctioned ones, even if they 
>aren't 100% portable because of flawed implementations, then I'm all 
>for them doing so.  I just don't have the knowledge to do this.

Unfortunately, just because the feature test is available it doesn't
necessarily mean that the implementation advertises the feature - sometimes
because the feature was introduced before the standard which introduced the
feature test - so you still need a boost macro - it's just than you can
boilerplate when it gets set for most (but not all) cases.

- John Maddock
http://ourworld.compuserve.com/homepages/john_maddock/