Re: [Boost-users] [thread] thread_specific_ptr is not initializedwith NULL

Subject: Re: [Boost-users] [thread] thread_specific_ptr is not initializedwith NULL
From: Anthony Williams (anthony.ajw_at_[hidden])
Date: 2009-06-08 03:33:30

"Michael Gopshtein" <mgopshtein_at_[hidden]> writes:

> That's not the case with "native" TLS support (it promises to zero out
> all values in released slot), but it's good to know that this is
> undefined for thread_specific_ptr.
>
> BTW, is it because such pattern of use is not considered interesting?
> For example, in our application there are "Database" objects which are
> created and destroyed dynamically, and each Database has a unique
> connection per thread, which are stored in the TLS. The connections
> are also stored in seperate lists, and are released when the Database
> is no longer in use - so the "default" behavior of the native API
> (both Win32 and pthreads) is OK with us.

Allowing this is a potential for memory leaks. pthread_key_delete does
not run the destructor function, so if you have dynamically allocated
memory (or other resource) referenced by the key value you have a
leak. By its very nature, thread_specific_ptr has dynamically allocated
memory for each key value, so it is important to ensure that it is
correctly deleted in each thread.

Anthony
-- 
Author of C++ Concurrency in Action | http://www.manning.com/williams
just::thread C++0x thread library   | http://www.stdthread.co.uk
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