From b7bfb54eaa84a7de187df905ae8f74c8fed515f4 Mon Sep 17 00:00:00 2001 From: Robert Griesemer Date: Fri, 13 Feb 2015 20:15:40 -0800 Subject: [PATCH] math/big: fix aliasing bug in Float.Quo TBR r, adonovan Change-Id: I1a38e2d724bf1147c7307a7e5ae855c42c60428c Reviewed-on: https://go-review.googlesource.com/4875 Reviewed-by: Robert Griesemer --- src/math/big/float.go | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/src/math/big/float.go b/src/math/big/float.go index dd6700137b..314fd689ed 100644 --- a/src/math/big/float.go +++ b/src/math/big/float.go @@ -967,12 +967,16 @@ func (z *Float) uquo(x, y *Float) { // to shorten x for faster division. But we must be extra careful // with rounding in that case. + // Compute d before division since there may be aliasing of x.mant + // (via xadj) or y.mant with z.mant. + d := len(xadj) - len(y.mant) + // divide var r nat z.mant, r = z.mant.div(nil, xadj, y.mant) // determine exponent - e := int64(x.exp) - int64(y.exp) - int64(len(xadj)-len(y.mant)-len(z.mant))*_W + e := int64(x.exp) - int64(y.exp) - int64(d-len(z.mant))*_W // normalize mantissa z.setExp(e - int64(fnorm(z.mant)))