[release-branch.go1.15] math/big: fix TestShiftOverlap for test -count arguments > 1

Don't overwrite incoming test data.

The change uses copy instead of assigning statement to avoid this.

For #45335

Change-Id: Ib907101822d811de5c45145cb9d7961907e212c3
Reviewed-on: https://go-review.googlesource.com/c/go/+/250137
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
(cherry picked from commit 41bc0a1713b9436e96c2d64211ad94e42cafd591)
Reviewed-on: https://go-review.googlesource.com/c/go/+/319831
Run-TryBot: Carlos Amedee <carlos@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Carlos Amedee <carlos@golang.org>
Reviewed-by: Jonathan Albrecht <jonathan.albrecht@ibm.com>
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>

diff --git a/src/math/big/arith_test.go b/src/math/big/arith_test.go
index 05136f1895f2b3c652fed4c35630b65c72ad9d45..e2b982c89c256be3c57c9acb6350dae938868de0 100644 (file)
--- a/src/math/big/arith_test.go
+++ b/src/math/big/arith_test.go
@@ -241,20 +241,20 @@ var argshrVU = []argVU{
 }
 
 func testShiftFunc(t *testing.T, f func(z, x []Word, s uint) Word, a argVU) {
-       // save a.d for error message, or it will be overwritten.
+       // work on copy of a.d to preserve the original data.
        b := make([]Word, len(a.d))
        copy(b, a.d)
-       z := a.d[a.zp : a.zp+a.l]
-       x := a.d[a.xp : a.xp+a.l]
+       z := b[a.zp : a.zp+a.l]
+       x := b[a.xp : a.xp+a.l]
        c := f(z, x, a.s)
        for i, zi := range z {
                if zi != a.r[i] {
-                       t.Errorf("d := %v, %s(d[%d:%d], d[%d:%d], %d)\n\tgot z[%d] = %#x; want %#x", b, a.m, a.zp, a.zp+a.l, a.xp, a.xp+a.l, a.s, i, zi, a.r[i])
+                       t.Errorf("d := %v, %s(d[%d:%d], d[%d:%d], %d)\n\tgot z[%d] = %#x; want %#x", a.d, a.m, a.zp, a.zp+a.l, a.xp, a.xp+a.l, a.s, i, zi, a.r[i])
                        break
                }
        }
        if c != a.c {
-               t.Errorf("d := %v, %s(d[%d:%d], d[%d:%d], %d)\n\tgot c = %#x; want %#x", b, a.m, a.zp, a.zp+a.l, a.xp, a.xp+a.l, a.s, c, a.c)
+               t.Errorf("d := %v, %s(d[%d:%d], d[%d:%d], %d)\n\tgot c = %#x; want %#x", a.d, a.m, a.zp, a.zp+a.l, a.xp, a.xp+a.l, a.s, c, a.c)
        }
 }