cgo如何在c中表示go类型？

Question

when export go func to c, the interface type port to GoInterface, and int to GoInt. How to port my c funcs to go with these types?

a.h

void *SomeFunc(GoInterface arg);

a.c

void *SomeFunc(GoInterface arg) {
}

a.go

package main

// #include "a.h"
import "C"

type A struct {
}

func main() {
    var a = new(A)
}

when I go build:

cc errors for preamble:
In file included from ./a.go:3:0:
a.h:1:16: error: unknown type name 'GoInterface'
 void *SomeFunc(GoInterface arg)

Is there a header file for go like jni.h for java, So I can include there types.

Answer 1

No, Go doesn't have any way to export types as "C readable". Further, you cannot reference a Go struct from within C, and it is not safe to try and finagle a C struct to "look like" a Go struct since you have no control over memory layout.

The "right" way to do this is to create a type in a C file and add it as a field in the Go struct:

// from C
typedef struct x {
    // fields
} x;


// From Go, include your .h file that defines this type.
type X struct {
   c C.x
}

Then operate on your type that way, and pass C.x into all your C functions instead of x.

There are a couple other ways, (for instance, converting between them any time you want to use it as one or the other), but this one is the best in a vague general sense.

Edit: a FEW Go types can be represented in C, for instance, int64 will be defined in code that's compiled via cgo, but for the most part what I said holds.