libstdc++ / mt_allocator.cc when using gthreads

[Laurent Alfonsi <laurent dot alfonsi at st dot com>]

    All,

The enclosed testcases (very close to 
ext/mt_allocator/deallocate_global_thread-1.cc) exposes a pattern where 
the following sequence is called (when __gthread_active_p is enabled) :

    __gthread_key_create(&key,::_M_destroy_thread_key);
    __gthread_setspecific(key, (void*)_M_id);
    __gthread_key_delete(key);
    __gthread_setspecific(key, (void*)_M_id);


Even, if this works perfectly using pthreads, it seems to me that this 
is an illegal use of threads. When using another thread implementation, 
(i.e. when the key is implemented as a pointer). In my case:
 - the key_create allocates the memory, and returns the pointer to the 
allocated memory
 - the key_delete frees this memory,
 - the setspecific uses this freed memory.

If I m right saying this is an illegal use of threads, a possible quick 
patch for mt_allocator.cc could be the one enclosed.

Let me know what you think of this approach.

Thanks.
Laurent

Attachment: deallocate_global_thread-5.cc
Description: Text document

Attachment: illegal_thread_key_used.patch
Description: Text document