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/f340b840-44b8-47eb-a5bd-7c52167913ddn%40googlegroups.com.
