math/big: ensure correct test input
There is a (theoretical, but possible) chance that the
random number values a, b used for TestDiv are 0 or 1,
in which case the test would fail.
This CL makes sure that a >= 1 and b >= 2 at all times.
Fixes #35523.
Change-Id: I6451feb94241249516a821cd0066e95a0c65b0ed
Reviewed-on: https://go-review.googlesource.com/c/go/+/206818
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/src/math/big/nat_test.go b/src/math/big/nat_test.go
index da34e95..cbbaf02 100644
--- a/src/math/big/nat_test.go
+++ b/src/math/big/nat_test.go
@@ -192,10 +192,22 @@
}
}
+// rndNat returns a random nat value >= 0 of (usually) n words in length.
+// In extremely unlikely cases it may be smaller than n words if the top-
+// most words are 0.
func rndNat(n int) nat {
return nat(rndV(n)).norm()
}
+// rndNat1 is like rndNat but the result is guaranteed to be > 0.
+func rndNat1(n int) nat {
+ x := nat(rndV(n)).norm()
+ if len(x) == 0 {
+ x.setWord(1)
+ }
+ return x
+}
+
func BenchmarkMul(b *testing.B) {
mulx := rndNat(1e4)
muly := rndNat(1e4)
@@ -747,18 +759,22 @@
}
for _, i := range sizes {
for _, j := range sizes {
- a := rndNat(i)
- b := rndNat(j)
+ a := rndNat1(i)
+ b := rndNat1(j)
+ // the test requires b >= 2
+ if len(b) == 1 && b[0] == 1 {
+ b[0] = 2
+ }
x := nat(nil).mul(a, b)
addVW(x, x, 1)
var q, r nat
q, r = q.div(r, x, b)
if q.cmp(a) != 0 {
- t.Fatal("wrong quotient", i, j)
+ t.Fatalf("wrong quotient: got %s; want %s for %s/%s", q.utoa(10), a.utoa(10), x.utoa(10), b.utoa(10))
}
if len(r) != 1 || r[0] != 1 {
- t.Fatal("wrong remainder")
+ t.Fatalf("wrong remainder: got %s; want 1 for %s/%s", r.utoa(10), x.utoa(10), b.utoa(10))
}
}
}
