How to handle errno from Go program via cgo.

errno.go

package main

import "unsafe"

/*
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

extern int errno;

static void setErrno(int err) {
        errno = err;
}
*/
import "C"

func main() {
        msg := C.CString("error detected")

        for _, en := range []C.int{C.EACCES, C.EDOM, C.ERANGE} {
                C.setErrno(en)
                C.perror(msg)
        }

        C.free(unsafe.Pointer(msg))
}

From this discussion

Sample output:

error detected: Permission denied
error detected: Numerical argument out of domain
error detected: Numerical result out of range