On Sunday, May 10, 2020 at 12:33:08 AM UTC+2, Ian Lance Taylor wrote:
>
> On Sat, May 9, 2020 at 12:56 PM Gert <[email protected] <javascript:>>
> wrote:
> >
> > This is the closest I get, I am out of ideas. Don't know why it runs but
> doesn't update the string.
>
> I don't know what you are really trying to do, but I want to be clear
> that this code is not supported. The supported way to call from Go to
> C is to use cgo. See https://golang.org/cmd/cgo and
> https://blog.golang.org/cgo.
>
> One big problem I see in your code is that you are assuming that Go
> and C use the same ABI. That is, that the arguments passed to the Go
> function will be seen as the arguments passed to the C function. That
> is not the case. When using the gc compiler, Go and C pass arguments
> in different locations.
>
> Ian
>
>
The attempt was based on this aprouch
https://go-review.googlesource.com/c/go/+/227037/17/src/crypto/x509/internal/macOS/corefoundation.go
<https://go-review.googlesource.com/c/go/+/227037/17/src/crypto/x509/internal/macOS/corefoundation.go#112>
but
trying to apply it to the most simple example I can think. Filippo Valsorda
believes its possible to link sqlite into go without using cgo. I made the
assumption a trampoline assembler jump is the only way to do that?
> > go run .
> > test [116 101 115 116 0 0 0 0 0 0] 4 0 0
> >
> > #include <stdio.h>
> > #include <string.h>
> >
> > int hello(char *s) {
> > char c[80];
> > strcpy (c, s);
> > sprintf(s, "hello %s", c);
> > printf("------\n");
> > return 0;
> > }
> >
> > #include "textflag.h"
> >
> > TEXT ·hello_trampoline(SB),NOSPLIT,$0-0
> > JMP hello_c(SB)
> >
> > package main
> >
> > import (
> > "fmt"
> > "unsafe"
> >
> > "golang.org/x/sys/unix"
> > )
> >
> > //go:linkname hello_t hello_c
> > //go:cgo_import_dynamic hello_c hello "./c/hello.dylib"
> >
> > //go:nosplit
> > func hello_t(s unsafe.Pointer) (uintptr, uintptr, unix.Errno) {
> > return unix.Syscall(funcPC(hello_trampoline), uintptr(s), 0, 0)
> > }
> >
> > func hello_trampoline()
> >
> > //go:nosplit
> > func funcPC(f func()) uintptr {
> > return **(**uintptr)(unsafe.Pointer(&f))
> > }
> >
> > func main() {
> > b := make([]byte, 10, 10)
> > copy(b, []byte("test"))
> > r1, r2, err := hello_t(unsafe.Pointer(&b[0]))
> > fmt.Printf("%s %v %d %d %d\n", b, b, r1, r2, err)
> > }
> >
> > --
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>
>
>
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