I found this issue: https://github.com/golang/go/issues/41205.
I found the answer, this conversation could be closed.
On Thursday, May 20, 2021 at 3:39:28 PM UTC+8 Kn wrote:
> So sorry I didn't get how to format the code in the edit window.
>
> On Thursday, May 20, 2021 at 3:37:35 PM UTC+8 Kn wrote:
>
>> Hi, guys, I need to acess shared memory, so I write some code like this:
>>
>> ```go
>> func shmget(key int, size int, mode int) (int, error) {
>> shmId, _, ret := syscall.Syscall(syscall.SYS_SHMGET, uintptr(key),
>> uintptr(size), uintptr(mode))
>> if ret != 0 {
>> return 0, fmt.Errorf("shmget ret: %d", ret)
>> }
>> return int(shmId), nil
>> }
>>
>> // shmat 映射共享内存地址到当前进程空间
>> func shmat(shmId int, addr unsafe.Pointer, flags int) (unsafe.Pointer,
>> error) {
>> shmAddr, _, ret := syscall.Syscall(syscall.SYS_SHMAT, uintptr(shmId),
>> uintptr(addr), uintptr(flags))
>> if ret != 0 {
>> return nil, fmt.Errorf("shmat ret: %d", ret)
>> }
>> *return unsafe.Pointer(shmAddr), nil // => possible misuse of
>> unsafe.Pointer*
>> }
>>
>> func GetShm(iKey, iSize, iFlag int) (unsafe.Pointer, error) {
>> iShmID, err := shmget(iKey, iSize, iFlag)
>> if err != nil {
>> return nil, err
>> }
>> sShmPtr, err := shmat(iShmID, nil, iFlag)
>> if err != nil {
>> return nil, err
>> }
>> return sShmPtr, nil
>> }
>> ```
>>
>> When I run go vet to check this code, it reports "possible misuse of
>> unsafe.Pointer" for the bold line "*return unsafe.Pointer(shmaddr), nil*"
>> . And I have read the Pointer rules. I see this case isn't listed in the
>> rules.
>>
>> I want to know :
>> - is it safe to use pointer like this? I think syscall `shmat` returns
>> the attached memory address that doesn't controlled by GC. I think it's
>> safe.
>> - if it's safe, how could I work around this check? just neglect it or do
>> we have some directives to prevent go vet checking?
>>
>> Thanks.
>>
>
--
You received this message because you are subscribed to the Google Groups
"golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to golang-nuts+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/golang-nuts/93b23566-c588-411f-9ad6-8c83fc7362fan%40googlegroups.com.
