I was sure the doc means the case when a program exits *too quickly,*
before cleanup has a chance to run, or am I wrong?
Otherwise, why need to specify "not guaranteed to run before program
exit."? It obviously can't run after program exits :)
In the code example above, I can wait indefinitely for cleanup to run, it
will not trigger:
for range 20 { // <-- can increase this arbitrary
runtime.GC()
if releaseFlag.Load() {
fmt.Println("released, cond:", goexit)
return
}
time.Sleep(10 * time.Millisecond)
}
On Thursday, April 3, 2025 at 8:50:24 PM UTC+3 robert engels wrote:
> It states this in the API docs:
>
> "The cleanup(arg) call is not always guaranteed to run; in particular it
> is not guaranteed to run before program exit."
>
> On Apr 3, 2025, at 10:23 AM, Yaroslav Brustinov <y.bru...@gmail.com>
> wrote:
>
> Hello, experts.
>
> Given following code as example:
>
> package main
>
> import (
> "fmt"
> "io"
> "runtime"
> "sync/atomic"
> "time"
> )
>
> type S struct {
> foo int
> }
>
> var released1 atomic.Bool
> var released2 atomic.Bool
>
> func releaseCb(releaseFlag *atomic.Bool) {
> fmt.Println("release CB")
> releaseFlag.Store(true)
> }
>
> func deferredCheckRelease(goexit bool, releaseFlag *atomic.Bool) {
> for range 20 {
> runtime.GC()
> if releaseFlag.Load() {
> fmt.Println("released, cond:", goexit)
> return
> }
> time.Sleep(10 * time.Millisecond)
> }
> fmt.Println("not released, cond:", goexit)
> }
>
> func f(goexit bool, releaseFlag *atomic.Bool) {
> defer deferredCheckRelease(goexit, releaseFlag)
> s := &S{1}
> runtime.AddCleanup(s, releaseCb, releaseFlag)
> if goexit {
> // releaseFlag will not be set
> runtime.Goexit()
> }
> // releaseFlag will be set
> fmt.Fprint(io.Discard, s)
> }
>
> func main() {
> go f(true, &released1)
> go f(false, &released2)
> time.Sleep(time.Second)
> }
>
> As comment inside mentions, release flag is not set if runtime.Goexit()
> executed.
>
> Maybe it's because runtime.AddCleanup is not "guaranteed" to run?
> In such case would be great to clarify (in docs?) in which cases it might
> not run.
> People might rely on the callback...
>
>
>
>
> --
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> .
>
>
>
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