sync/atomic: remove noCopy from Value

Values must not be copied after the first use.

Using noCopy makes vet complain about copies
even before the first use, which is incorrect
and very frustrating.

Drop it.

Fixes #21504.

Change-Id: Icd3a5ac3fe11e84525b998e848ed18a5d996f45a
Reviewed-on: https://go-review.googlesource.com/80836
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

diff --git a/src/cmd/vet/testdata/copylock.go b/src/cmd/vet/testdata/copylock.go
index d733488e6218b55778458d7ff37125c3e5a16787..e9902a27f10dd204a77138beb28aabdbefc946f3 100644 (file)
--- a/src/cmd/vet/testdata/copylock.go
+++ b/src/cmd/vet/testdata/copylock.go
@@ -178,9 +178,11 @@ func AtomicTypesCheck() {
        var vX atomic.Value
        var vXX = atomic.Value{}
        vX1 := new(atomic.Value)
-       vY := vX     // ERROR "assignment copies lock value to vY: sync/atomic.Value contains sync/atomic.noCopy"
-       vY = vX      // ERROR "assignment copies lock value to vY: sync/atomic.Value contains sync/atomic.noCopy"
-       var vYY = vX // ERROR "variable declaration copies lock value to vYY: sync/atomic.Value contains sync/atomic.noCopy"
+       // These are OK because the value has not been used yet.
+       // (And vet can't tell whether it has been used, so they're always OK.)
+       vY := vX
+       vY = vX
+       var vYY = vX
        vP := &vX
        vZ := &atomic.Value{}
 }

diff --git a/src/sync/atomic/value.go b/src/sync/atomic/value.go
index ac5a9a5e7228f72e0b807aaab51548be86857d17..eab7e70c9b0f3ed5155cbf3c6a9e73cb4154c2c8 100644 (file)
--- a/src/sync/atomic/value.go
+++ b/src/sync/atomic/value.go
@@ -14,8 +14,6 @@ import (
 //
 // A Value must not be copied after first use.
 type Value struct {
-       noCopy noCopy
-
        v interface{}
 }
 
@@ -86,13 +84,3 @@ func (v *Value) Store(x interface{}) {
 // Disable/enable preemption, implemented in runtime.
 func runtime_procPin()
 func runtime_procUnpin()
-
-// noCopy may be embedded into structs which must not be copied
-// after the first use.
-//
-// See https://golang.org/issues/8005#issuecomment-190753527
-// for details.
-type noCopy struct{}
-
-// Lock is a no-op used by -copylocks checker from `go vet`.
-func (*noCopy) Lock() {}