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[release-branch.go1] sync: mention that WaitGroup.Add panics

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««« backport 05f9fa32500a
sync: mention that WaitGroup.Add panics
Fixes #3839.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6428053

»»»
This commit is contained in:
Rob Pike 2012-09-22 05:54:08 +10:00
parent d88fcebcd8
commit 5c47098ec8
2 changed files with 3 additions and 2 deletions
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3
src/pkg/sync/waitgroup.go
View File

@ -32,10 +32,11 @@ type WaitGroup struct {
// Add adds delta, which may be negative, to the WaitGroup counter.
// If the counter becomes zero, all goroutines blocked on Wait() are released.
// If the counter goes negative, Add panics.
func (wg *WaitGroup) Add(delta int) {
v := atomic.AddInt32(&wg.counter, int32(delta))
if v < 0 {
panic("sync: negative WaitGroup count")
panic("sync: negative WaitGroup counter")
}
if v > 0 || atomic.LoadInt32(&wg.waiters) == 0 {
return

2
src/pkg/sync/waitgroup_test.go
View File

@ -50,7 +50,7 @@ func TestWaitGroup(t *testing.T) {
func TestWaitGroupMisuse(t *testing.T) {
defer func() {
err := recover()
if err != "sync: negative WaitGroup count" {
if err != "sync: negative WaitGroup counter" {
t.Fatalf("Unexpected panic: %#v", err)
}
}()