crypto/bn256: fix go vet false positive

Also add the package to the license tool ignore list.

build/update-license.go

@@ -47,11 +47,14 @@ var (
 		// boring stuff
 		"vendor/", "tests/files/", "build/",
 		// don't relicense vendored sources
-		"crypto/sha3/", "crypto/ecies/", "log/",
-		"crypto/secp256k1/curve.go",
-		"consensus/ethash/xor.go",
-		"internal/jsre/deps",
 		"cmd/internal/browser",
+		"consensus/ethash/xor.go",
+		"crypto/bn256/",
+		"crypto/ecies/",
+		"crypto/secp256k1/curve.go",
+		"crypto/sha3/",
+		"internal/jsre/deps",
+		"log/",
 		// don't license generated files
 		"contracts/chequebook/contract/",
 		"contracts/ens/contract/",

crypto/bn256/curve.go

@@ -186,14 +186,14 @@ func (c *curvePoint) Double(a *curvePoint, pool *bnPool) {
 	A.Mod(A, P)
 	B := pool.Get().Mul(a.y, a.y)
 	B.Mod(B, P)
-	C := pool.Get().Mul(B, B)
-	C.Mod(C, P)
+	C_ := pool.Get().Mul(B, B)
+	C_.Mod(C_, P)
 
 	t := pool.Get().Add(a.x, B)
 	t2 := pool.Get().Mul(t, t)
 	t2.Mod(t2, P)
 	t.Sub(t2, A)
-	t2.Sub(t, C)
+	t2.Sub(t, C_)
 	d := pool.Get().Add(t2, t2)
 	t.Add(A, A)
 	e := pool.Get().Add(t, A)
@@ -203,7 +203,7 @@ func (c *curvePoint) Double(a *curvePoint, pool *bnPool) {
 	t.Add(d, d)
 	c.x.Sub(f, t)
 
-	t.Add(C, C)
+	t.Add(C_, C_)
 	t2.Add(t, t)
 	t.Add(t2, t2)
 	c.y.Sub(d, c.x)
@@ -217,7 +217,7 @@ func (c *curvePoint) Double(a *curvePoint, pool *bnPool) {
 
 	pool.Put(A)
 	pool.Put(B)
-	pool.Put(C)
+	pool.Put(C_)
 	pool.Put(t)
 	pool.Put(t2)
 	pool.Put(d)

crypto/bn256/gfp6.go

@@ -266,13 +266,13 @@ func (e *gfP6) Invert(a *gfP6, pool *bnPool) *gfP6 {
 	t1.Mul(a.y, a.z, pool)
 	B.Sub(B, t1)
 
-	C := newGFp2(pool)
-	C.Square(a.y, pool)
+	C_ := newGFp2(pool)
+	C_.Square(a.y, pool)
 	t1.Mul(a.x, a.z, pool)
-	C.Sub(C, t1)
+	C_.Sub(C_, t1)
 
 	F := newGFp2(pool)
-	F.Mul(C, a.y, pool)
+	F.Mul(C_, a.y, pool)
 	F.MulXi(F, pool)
 	t1.Mul(A, a.z, pool)
 	F.Add(F, t1)
@@ -282,14 +282,14 @@ func (e *gfP6) Invert(a *gfP6, pool *bnPool) *gfP6 {
 
 	F.Invert(F, pool)
 
-	e.x.Mul(C, F, pool)
+	e.x.Mul(C_, F, pool)
 	e.y.Mul(B, F, pool)
 	e.z.Mul(A, F, pool)
 
 	t1.Put(pool)
 	A.Put(pool)
 	B.Put(pool)
-	C.Put(pool)
+	C_.Put(pool)
 	F.Put(pool)
 
 	return e

crypto/bn256/optate.go

@@ -88,12 +88,12 @@ func lineFunctionDouble(r *twistPoint, q *curvePoint, pool *bnPool) (a, b, c *gf
 
 	A := newGFp2(pool).Square(r.x, pool)
 	B := newGFp2(pool).Square(r.y, pool)
-	C := newGFp2(pool).Square(B, pool)
+	C_ := newGFp2(pool).Square(B, pool)
 
 	D := newGFp2(pool).Add(r.x, B)
 	D.Square(D, pool)
 	D.Sub(D, A)
-	D.Sub(D, C)
+	D.Sub(D, C_)
 	D.Add(D, D)
 
 	E := newGFp2(pool).Add(A, A)
@@ -112,7 +112,7 @@ func lineFunctionDouble(r *twistPoint, q *curvePoint, pool *bnPool) (a, b, c *gf
 
 	rOut.y.Sub(D, rOut.x)
 	rOut.y.Mul(rOut.y, E, pool)
-	t := newGFp2(pool).Add(C, C)
+	t := newGFp2(pool).Add(C_, C_)
 	t.Add(t, t)
 	t.Add(t, t)
 	rOut.y.Sub(rOut.y, t)
@@ -142,7 +142,7 @@ func lineFunctionDouble(r *twistPoint, q *curvePoint, pool *bnPool) (a, b, c *gf
 
 	A.Put(pool)
 	B.Put(pool)
-	C.Put(pool)
+	C_.Put(pool)
 	D.Put(pool)
 	E.Put(pool)
 	G.Put(pool)

crypto/bn256/twist.go

@@ -165,12 +165,12 @@ func (c *twistPoint) Double(a *twistPoint, pool *bnPool) {
 	// See http://hyperelliptic.org/EFD/g1p/auto-code/shortw/jacobian-0/doubling/dbl-2009-l.op3
 	A := newGFp2(pool).Square(a.x, pool)
 	B := newGFp2(pool).Square(a.y, pool)
-	C := newGFp2(pool).Square(B, pool)
+	C_ := newGFp2(pool).Square(B, pool)
 
 	t := newGFp2(pool).Add(a.x, B)
 	t2 := newGFp2(pool).Square(t, pool)
 	t.Sub(t2, A)
-	t2.Sub(t, C)
+	t2.Sub(t, C_)
 	d := newGFp2(pool).Add(t2, t2)
 	t.Add(A, A)
 	e := newGFp2(pool).Add(t, A)
@@ -179,7 +179,7 @@ func (c *twistPoint) Double(a *twistPoint, pool *bnPool) {
 	t.Add(d, d)
 	c.x.Sub(f, t)
 
-	t.Add(C, C)
+	t.Add(C_, C_)
 	t2.Add(t, t)
 	t.Add(t2, t2)
 	c.y.Sub(d, c.x)
@@ -191,7 +191,7 @@ func (c *twistPoint) Double(a *twistPoint, pool *bnPool) {
 
 	A.Put(pool)
 	B.Put(pool)
-	C.Put(pool)
+	C_.Put(pool)
 	t.Put(pool)
 	t2.Put(pool)
 	d.Put(pool)