[PATCH] talloc_free_for_exit() and targeted write protection for talloc destructor

[Andrew Bartlett]

In a hope of getting more attention and being more transparent, here is
the talloc changes I included in my previous patch set.

As background, I want to make our LDAP server multi-process, and
running a connect()/bind()/close() loop against the LDAP server showed
a significant cost in talloc_free(ev) and talloc_autofree() just before
exit.

This made me think about a way to make Samba 'forget' to call free() or
inspect talloc children that did not have a destructor to fire. 

It also has very useful security implications, as if we don't
universally call the destructor, then a targeted overwrite of a
destructor is not nearly as useful.  This follows on from my magic
hardening work. 

The cost is that talloc_steal(), the implicit talloc_steal() when a
reference becomes a parent and talloc_add_destructor() become O(log(n))
or so, not O(1) as they were. 

Please carefully examine.  I'll also see if I can squeeze some more
performance out of it, eg dropping patch 33, as every single branch in
talloc has quite a cost.

Thanks,

Andrew Bartlett
-- 
Andrew Bartlett                       http://samba.org/~abartlet/
Authentication Developer, Samba Team  http://samba.org
Samba Developer, Catalyst IT          http://catalyst.net.nz/services/samba
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