On 06/17/2011 04:21 AM, Andy Wingo wrote:
>   wingo@badger:/tmp$ gcc -O1 -o test foo.c
>   wingo@badger:/tmp$ ./test; echo $?
>   1
>   wingo@badger:/tmp$ gcc -O3 -o test foo.c
>   wingo@badger:/tmp$ ./test; echo $?
>   0

If I understand correctly, 0 is a correct result, just not optimal.

Improvements for getting the optimal result in spite of gcc
optimizations are welcome (the more we can determine at compile time,
the less work we have to do at runtime), but any correctly written
program should already handle the case of an indeterminate compile-time
probe (the probe should return 1 or -1 for known directions, and 0 for
undetermined direction).

-- 
Eric Blake   eblake@redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org