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how to atomic.load/store a pointer #34840

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zylthinking opened this issue Oct 11, 2019 · 1 comment
Closed

how to atomic.load/store a pointer #34840

zylthinking opened this issue Oct 11, 2019 · 1 comment
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@zylthinking
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What version of Go are you using (go version)?

go version go1.13 linux/amd64

Does this issue reproduce with the latest release?

YES

What operating system and processor architecture are you using (go env)?

go env Output
GO111MODULE="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/zylthinking/.cache/go-build"
GOENV="/home/zylthinking/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GONOPROXY="*.qianxin-inc.cn"
GONOSUMDB="*.qianxin-inc.cn"
GOOS="linux"
GOPATH="/home/zylthinking/go"
GOPRIVATE="*.qianxin-inc.cn"
GOPROXY="https://goproxy.io"
GOROOT="/opt/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/opt/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build825018572=/tmp/go-build -gno-record-gcc-switches"

What did you do?

package main

import (
    "fmt"
    "sync/atomic"
    "unsafe"
)

func main() {
    n := 0;
    n1 := 0;
    intp := &n;
    fmt.Println(&n, &n1);
    a := (unsafe.Pointer(&intp));
    fmt.Println(a, intp)
    atomic.StorePointer(&a, unsafe.Pointer(&n1));
    fmt.Println(a, intp)
}

What did you expect to see?

0xc00009e010 0xc00009e018
0xc0000a2018 0xc00009e010
0xc0000a2018 0xc00009e018

What did you see instead?

0xc0000a0000 0xc0000a0008
0xc000096018 0xc0000a0000
0xc0000a0008 0xc0000a0000

words

I do know how to generate the desired result, just

    a := (*unsafe.Pointer) (unsafe.Pointer(&intp));
    atomic.StorePointer(a, unsafe.Pointer(&n1));

however, &intp is Integer pointer, but it is not a *unsafe.Pointer
it is not like (*reflect.SliceHeader) and (*reflect.StringHeader) confirmed by std library to be compatible.
@agnivade
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Hello @zylthinking, unlike other projects, we do not use the issue tracker for questions such as these. It is only used for bugs and feature proposals. I will close this issue, but please feel free to ask it in any of these forums below:

Thanks

@golang golang locked and limited conversation to collaborators Oct 10, 2020
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@zylthinking @agnivade @gopherbot