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sync/atomic: remove noCopy from Value

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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>
This commit is contained in:
Russ Cox 2017-11-29 16:20:50 -05:00 committed by Brad Fitzpatrick
parent 08176b28a3
commit 0c0c3c186b
2 changed files with 5 additions and 15 deletions
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8
src/cmd/vet/testdata/copylock.go vendored
View file

@ -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{}
}

12
src/sync/atomic/value.go
View file

@ -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() {}