It seems reasonable that if complain=0, fd>=0, and size>0, but osize<0, that it should try the mmap anyway (and skip the "area outside file" test, which is the only thing it needs osize for in this case).
Then something like
> object m = System.Memory();
> m->mmap("/sys/bus/nvmem/devices/mtd0/nvmem", 0, 4096);
(1) Result: 0
>
should work (i.e. return 1 instead of 0 :).
