On Mon, Aug 6, 2018 at 11:34 PM, nicolas_boiteux via golang-nuts
<golang-nuts@googlegroups.com> wrote:
>
> yes i used the code from this page:
>
> func Float64bits(f float64) uint64 {
> return *(*uint64)(unsafe.Pointer(&f))
> }
>
> adapted to my use case
>
> *(*int)(unsafe.Pointer(limit)
As the docs say, that is only permissible when T2 is no larger than T1
and the two share an equivalent memory layout. In your case T2 is the
Go type `int` and T1 is the C type `int`. On 64-bit systems the C
type `int` is 32 bits and the Go type `int` is 64 bits. So T2 is
larger than T1 and your conversion is not permitted by the unsafe
rules.
Ian
> Le lundi 6 août 2018 19:53:07 UTC+2, Ian Lance Taylor a écrit :
>>
>> On Sun, Aug 5, 2018 at 10:29 PM, nicolas_boiteux via golang-nuts
>> <golan...@googlegroups.com> wrote:
>> >
>> > thanks you, the A3 community finaly help me to solve the last problem
>> >
>> > for index := C.int(0); index < argc; index++ {
>> > out = append(out, C.GoString(*argv))
>> > argv = (**C.char)(unsafe.Pointer(uintptr(unsafe.Pointer(argv)) +
>> > offset))
>> > }
>> >
>> > I dont really understand why but it seems there was a problem with my
>> > casting method with unsafe
>> >
>> > *(*int)(unsafe.Pointer(limit)
>>
>> See https://golang.org/pkg/unsafe for the exact ways that you are
>> permitted to use unsafe.Pointer.
>>
>> Ian
>>
>> > Le dimanche 5 août 2018 15:02:47 UTC+2, Jan Mercl a écrit :
>> >>
>> >> On Sun, Aug 5, 2018 at 2:50 PM nicolas_boiteux via golang-nuts
>> >> <golan...@googlegroups.com> wrote:
>> >>
>> >> > not sure to understand cause the iteration in your example is done on
>> >> > os
>> >> > interface from golang not from c char array :(
>> >>
>> >> Not sure what you mean by 'os interface'. Here's the part that iterates
>> >> **C.char, except pointers are transformed to uintptrs. Other that that
>> >> it's
>> >> what you're, I think, after
>> >>
>> >> // Xmain is defined at main.c:3:5
>> >> func Xmain(tls crt.TLS, _argc int32, _argv uintptr /* **int8 */) (r
>> >> int32)
>> >> {
>> >> var _p uintptr // **int8
>> >>
>> >> _p = _argv
>> >> _1:
>> >> if (*(*uintptr)(unsafe.Pointer(_p))) == 0 {
>> >> goto _3
>> >> }
>> >>
>> >> crt.Xprintf(tls, ts+0 /* "%s\n" */, *(*uintptr)(unsafe.Pointer(_p)))
>> >> _p += 8
>> >> goto _1
>> >>
>> >> _3:
>> >> return r
>> >> }
>> >>
>> >> Manually converting (untested again):
>> >>
>> >> func foo(argv **C.char) []string {
>> >> var a []string
>> >> for p := argv; *p != nil; *(*uintptr)(unsafe.Pointer(p)) +=
>> >> unsafe.Sizeof(*p) {
>> >> a = append(a, GoString(*p))
>> >> }
>> >> rerurn a
>> >> }
>> >>
>> >>
>> >> --
>> >>
>> >> -j
>> >
>> > --
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