optimization/7799: [3.2/3.3 regression] Loop bug withoptimization flag -Os in gcc

[Morten Welinder]

Andreas Schwab writes:

> "Christian Ehrhardt" <ehrhardt@mathematik.uni-ulm.de> writes:
>|> By calling fill ((int*) 0xffffffc, q);

> Undefined behaviour.

True, but its_somewhere_in_my_libc() is not.  Implementation defined,
yes, but not undefined.

A quick scan of mmap's manual page suggests that it is not completely
ruled out that you would get 0xfffffffc for an area that includes
space for ten ints thereafter.  (Perhaps you would have to ask for
memory starting a bit earlier, namely at the start of a page.)

With PROT_NONE this would merely be absurd behaviour, IMHO, as opposed
to certifiably insane.

Morten