Aliasing issue with TAILQ on ppc64 ?

[Poul-Henning Kamp]

In message <CAJ-FndCsf2Xsn=1ioHyr_tn3-yAFOE7E9-wrjp4rcQJajhZvpg at mail.gmail.com>
, Attilio Rao writes:

>The only way I can see this
>code is safe is, infact, to lock it with proper locks around the
>operations.

This is not about locking: at the time where this croaks there is
only one thread.

The problem is that:

	// Empty, freshly initialized ban_head

	b = valid_ban_object();
	TAILQ_INSERT_HEAD(&ban_head, b, list);

	be = TAILQ_LAST(&ban_head, banhead_s);

Causes a sig#11 in TAILQ_LAST().

I belive it is a NULL dereference, and I belive it happens
because the compiler overoptimizes TAILQ_{LAST|PREV}()

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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