a.out gives different results when compiled by g++ 3.1 and g++ 3.1 -O

[Falk Hueffner]

Erick Alphonse <alphonse@lri.fr> writes:

> Falk Hueffner wrote:
> 
> >> enum {N = 624,              // length of state vector
> >>       M = 397,              // period parameter
> >>       MAGIC = 0x9908B0DFU}; // magic constant
> >>
> >> ui32 state[N];              // internal state
> >>[...]
> >>*p++ = twist( p[M-N], p[0], p[1] );
> >>
> > You're accessing out of the array bounds here, so anything might
> > happen.
> 
> I can't see the problem, the for-loop is entered N-1 times. Valgrind
> reported nothing wrong.

MAGIC = 0x9908B0DFU forces the enum to become unsigned, therefore M-N
is done with unsigned arithmetic and you're accessing p[4294967069].

-- 
	Falk