In this case, the vet tool is correct if you're making the syscall with Go-allocated memory. The Go runtime is allowed to move values around: the address of a Go variable is only pinned for the duration of the syscall itself.
If you've got C-allocated memory (or statically-allocated memory), https://golang.org/issue/13656#issuecomment-303216308 has a solution that avoids copying and is more robust to large sizes. On Thursday, December 14, 2017 at 5:27:57 AM UTC-5, snmed wrote: > > Okay I found a way, this seems to work: > > ca := (*[1000000]byte) (unsafe.Pointer(certctx.pbCertEncoded))[:certctx. > cbCertEncoded] > > or > > mm := make([]byte, certctx.cbCertEncoded) > for i := uint32(0) ; i < certctx.cbCertEncoded; i++ { > mm[i] = *((*byte)(unsafe.Pointer(certctx.pbCertEncoded + uintptr(i > ) * unsafe.Sizeof(new(byte))))) > } > > > > Anyway, the vet tool is complaining: > > main.go:106: possible misuse of unsafe.Pointer > main.go:109: possible misuse of unsafe.Pointer > > This is the code fragment: > > 104 certctx := new(CERT_CONTEXT) > 105 > 106 certctx = (*CERT_CONTEXT) (unsafe.Pointer(pccert_context)) > 107 > 108 > 109 ca := (*[1000000]byte) (unsafe.Pointer(certctx.pbCertEncoded))[: > certctx.cbCertEncoded] > > Is there another way to use syscall return values uintptr without vet > warnings? And which solution should I prefer? I think the later one should > be more safe, isn't it? > > Cheers > > > Am Donnerstag, 14. Dezember 2017 09:29:38 UTC+1 schrieb snmed: >> >> Hi Miki >> >> I'm using syscall package and no C import, but maybe it is possible to >> use this function as well? >> >> Am Donnerstag, 14. Dezember 2017 09:18:26 UTC+1 schrieb Miki Tebeka: >>> >>> Do you mean >>> >>> func C.GoBytes(unsafe.Pointer, C.int) []byte >>> >>> ? >>> >>> On Thursday, December 14, 2017 at 9:05:32 AM UTC+2, snmed wrote: >>>> >>>> Hi all >>>> >>>> I'm trying to map a C structure to an equivalent go struct, but I >>>> bumped into a problem with a pointer to byte that is actually an array of >>>> bytes. >>>> >>>> Here is the C struct: >>>> >>>> typedef struct _CERT_CONTEXT { >>>> DWORD dwCertEncodingType; >>>> BYTE *pbCertEncoded; >>>> DWORD cbCertEncoded; >>>> PCERT_INFO pCertInfo; >>>> HCERTSTORE hCertStore; >>>> } CERT_CONTEXT, *PCERT_CONTEXT; >>>> >>>> >>>> and this is my go struct: >>>> >>>> type CERT_CONTEXT struct { >>>> dwCertEncodingType uint32 >>>> pbCertEncoded uintptr >>>> cbCertEncoded uint32 >>>> pCertInfo uintptr >>>> hCertStore uintptr >>>> } >>>> >>>> for my case I need only the first 3 fields and I do not have any >>>> problem to get 1 and 3, but I can't remember how to translate the second >>>> field to a slice of bytes. >>>> This is how I map the struct from an uintptr and print it to the >>>> console: >>>> >>>> certctx = (*CERT_CONTEXT) (unsafe.Pointer(pccert_context)) >>>> fmt.Printf("%v\n", certctx) >>>> >>>> >&{1 807520 674 833008 789360} >>>> >>>> Any advise is warmly welcome. >>>> >>>> Cheers, >>>> Sandro >>>> >>> -- 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. For more options, visit https://groups.google.com/d/optout.
