You haven't actually said which system call you're invoking, but from the name CERT_CONTEXT and the layout of the struct I'm guessing it's probably CertCreateCertificateContext <https://godoc.org/golang.org/x/sys/windows#CertCreateCertificateContext> or CertEnumCertificatesInStore <https://godoc.org/golang.org/x/sys/windows#CertEnumCertificatesInStore>?
I don't really know anything about Windows system calls, but it does seem like those allocate memory somewhere outside of the Go heap. On Fri, Dec 15, 2017 at 1:54 AM, snmed <sandro.p.da...@gmail.com> wrote: > Hi Bryan > > But the returned uintptr from syscall is as far as i know a pointer to a > struct which has been created by the C API, so go runtime won't touch it or > do I miss something? > > > Am Freitag, 15. Dezember 2017 00:48:51 UTC+1 schrieb Bryan Mills: >> >> 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 a topic in the > Google Groups "golang-nuts" group. > To unsubscribe from this topic, visit https://groups.google.com/d/ > topic/golang-nuts/0JYB0-ZcFpk/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > golang-nuts+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- 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.
