Bug in Mod (2.0.15)

[Ilya Zakharevich <ilya@math.ohio-state.edu>]

a)

    ? z=Mod(x,x^2+y^2)
    %1 = Mod(x, x^2 + y^2)
    ? u=Mod(z,x^2+y^2+t^2)
    %2 = 0

b) Additionally: why do not we allow quotients by ideals with several
   generators, like making the above thing to live in

    Q[x,y]/(x^2+y^2,x^2+y^2+t^2)

   ?

c) If $\fl$ is equal to $1$, the modulus of the created result is put
   on the heap and not on the stack, and hence becomes a permanent
   copy which cannot be erased later by garbage collecting (see
   \secref{se:garbage}). In particular, care should be taken to avoid
   creating too many such objects, since the heap is very small
   (typically a few thousand objects at most).

   This is an excerpt from Mod() documentation.  Definitely with
   hardware of today we can create billions of objects on the stack, right?

Ilya