mpn_gcdext bug in v4.3.0?

[shoup at cims.nyu.edu]

I have been running a number of tests with mpn_gcdext,
and came across what seems to be a bug.


I'm calling it as:

sd = mpn_gcdext(ddata, xadata, &sxa, adata, sa, bdata, sb);

The problem is that the cofactor (xadata, sxa) is not
normalized, where "normalized" means xadata[sxa-1] != 0.

I have found an input where xadata[sxa-1] == 0.
I'm not sure if this is really a bug or not.
I was assuming this was computed so that (xadata, sxa)
was properly "normalized", as usual.

Attached are a small program and input file
that illustrates the bug (compiled on a 64-bit
Mac OSX platform).

I can work around this bug for now by adding
normalization code in my calls to mpn_gcdext.
I will also assume (for now) that (ddata, sd) may also
not be normalized.

If this is not considered a bug, then at least the
documentation should make it clear that the
results may not be normalized.

   -- Victor Shoup




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