Exit status of zero-length executable?

[Dan Kegel <dank@xxxxxxxxx>]

I was surprised to discover that:

touch foo
chmod +x foo
./foo
echo $?

outputs
0

on the linux, mac, and bsd systems I've tried; on Linux I tried both
bash and dash.

Is this expected?  I did a quick scan of the standard but didn't see
anything related.

Thanks,
Dan