example.md

t.md

• This requires a C cross-compiler for ARM. In most cases, it's only available in Linux.
• Follow steps here to install the GO compiler/toolset first.
• cross compile a GO program mixed with C. specify the CC as the C cross compiler of your target platform

CGO_ENABLED=1 CC=arm-linux-gnueabihf-gcc  GOARCH=arm GOARM=7 GOOS=linux go build -o hellowithc hellowithc.go # for Cortex A7/A8/A9

CGO_ENABLED=1 CC=arm-mv5sft-linux-gnueabi-gcc  GOARCH=arm GOARM=5 GOOS=linux go build -o hellowithc hellowithc.go # for Marvell Poncat

Simple case: Just a bit C code placed in a comment block of GO

• hellowithc.go

package main

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

void myprint(char* s) {
    printf("%s", s);
}
*/
import "C"
import "fmt"

func main() {
  cs := C.CString("Hello from stdio\n")
  C.myprint(cs)
  fmt.Println("done")
}

• please note there must be no blank lines between import "C" and the above C code in comment block

Complicated case: static link with a external lib(.a)

• All C sources must be compileed with -fPIC option
• Add the options for linker in ex. #cgo LDFLAGS: -L. -lphy

example project

• phyrw.h

#ifndef __PHYRW_H__
#define __PHYRW_H__

void phyopen( char *s, int phyId);
int phyread( int reg);
void phywrite( int reg, int val);
void phyclose();
    
#endif

• the main go program

/*
#cgo LDFLAGS:  -L. -lphy
#include "./phyrw.h"
*/

/*
#cgo LDFLAGS:  -L. -lphy
#include "./phyrw.h"
*/
import "C"

func PhyOpen(ifname string, phyad int) {
    C.phyopen(C.CString(ifname), C.int(phyad))
}

func PhyRead(reg int) int {
    return int(C.phyread(C.int(reg)))
}

func PhyWrite(reg int, val int) {
    C.phywrite(C.int(reg), C.int(val))
}

func PhyClose() {
    C.phyclose()
}

• the Makefile

phyrw.o: phyrw.c
  $(CC) -fpic -c -o $@ $<

libphy.a: phyrw.o
  arm-linux-gnueabihf-ar cr $@ $<

tinycore: tinycore.go libphy.a
  CGO_ENABLED=1 CC=$(CC) GOARCH=arm GOARM=7 GOOS=linux go build -o $@  $<
  $(STRIP) $@