Temporary out of bounds should yield an analyser warning

[davidchisnall]

This line:

                doublebasemul(r->coeffs + ctr - 4, b->coeffs + ctr - 4, ax, (ctr - 4) / 4, add);

Adds a counter to the pointer and then subtracts four. The array is quite small (four bytes) and so ctr takes it out of representable bounds and -4 brings it back in.

The size of coeffs is know at compile time. It should be possible to determine that +ctr may take the pointer out of bounds.

[resistor]

I can add such a warning, but it won't trigger on this case because the array is actually 256 elements, not 4.