Anthony Williams wrote:
"Peter Dimov" <pdimov@mmltd.net> writes:
Anthony Williams wrote:
Can we have a call to TlsFree in on_process_exit, so we don't leak the TLS slot either?
It's better not to. We don't leak a TLS slot because TLS slots are per process. When the process is terminated by the OS, all of its TLS slots are "reclaimed" (more precisely, they simply cease to exist.)
So we gain nothing because the lack of TlsFree is not observable.
The same could be said of just about everything that the OS cleans up --- handles, memory, etc.
Correct. The only reason to do redundant cleanup is because of inadequate leak detectors and user complaints.
On the other hand, if on_process_exit is called when some threads are still running, TlsFree'ing the slot will make it impossible for these threads to clean up after themselves since they won't be able to access their cleanup handler lists. This can be observable if their cleanup handlers have visible side effects.
on_process_exit is called when the module is unloaded. If there are any threads running at that point which are referencing code in that module (e.g. because they use boost thread cleanup handlers), they have bigger problems than the fact that the TLS slot has been freed --- the whole module is being unloaded.
If on_process_exit is guaranteed to be called after all on_thread_exits (if it's called at all), it will indeed be safe (but still redundant) to TlsFree the slot in it.