Thanks, I see. How about this one? I use a temp variable to store sh.Data,
sh/ds/data are all no longer mentioned at the point when unsafe.Slice is
called. Do I need to use runtime.KeepAlive?
package main
import (
"fmt"
"reflect"
"runtime"
"unsafe"
)
var b []byte
func f(data interface{}) {
switch ds := data.(type) {
case []int32:
sh := (*reflect.SliceHeader)(unsafe.Pointer(&ds))
l := len(ds)
d := sh.Data
runtime.GC()
b = unsafe.Slice((*byte)(unsafe.Pointer(d)), l*4)
}
// runtime.KeepAlive(data)
}
func main() {
f([]int32{1, 2})
runtime.GC()
fmt.Println(b)
}
在2021年9月23日星期四 UTC+8 上午6:11:48<Ian Lance Taylor> 写道：
> On Wed, Sep 22, 2021 at 1:22 AM Cholerae Hu <chole...@gmail.com> wrote:
> >
> > https://play.golang.org/p/WJTH-lUukeb
> >
> > Do I need to uncomment line 23? IMHO, variable data and ds will not be
> used after line 16, so they can be collected in runtime.GC. But running it
> with gccheckmark=1 and clobberfree=1 doesn't show any problems.
> >
> > Are there any documents about the details or behavior of liveness
> analysis?
>
> I don't see any reason why that program should need runtime.KeepAlive.
>
> The local variable sh will point to data (aka ds), so the object will
> stay alive. This is not different than p := &data. After that point,
> if data is no longer mentioned, then the variable data is no longer
> live, but the value that p points to will remain alive.
>
> Ian
>
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