How to use C library in Golang(v1.3.2)

Question

This is my Go source :

package facerec

/*
#include "libs/facerec_lib.h"
*/
import "C"

// import "unsafe"

type FaceRecServiceImpl struct {
}

func (this *FaceRecServiceImpl) Compare(features1 []byte, features2 []byte) (r float64, err error) {
    // TODO
    result := C.sumUp(2, 3)
    return float64(result), nil
}

facerec_lib.h

int sumUp(int a, int b);

facerec_lib.c

/* File facerec.c */
#include "facerec_lib.h"

int sumUp(int a, int b)
{
  return a + b;
}

go build:

Roy-MacBook-Air:facerec $ go build
# xxx/facerec
Undefined symbols for architecture x86_64:
  "_sumUp", referenced from:
      __cgo_35aa8b5c98e0_Cfunc_sumUp in face_rec.cgo2.o
     (maybe you meant: __cgo_35aa8b5c98e0_Cfunc_sumUp)
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Roy-MacBook-Air:facerec$

How can I deal with this issue ? Thanks a lot !

EDIT

I changed facerec_lib.h to facerec_lib.c, problem solved, I thinks I must miss some FLAGS in go file, any hints ?

Answer 1

如果您通过cgo使用C函数，则必须确保该函数的实现链接到您的Go包中。从您对问题的评论来看，情况似乎并非如此。

您可以采取的两种方式包括：

1. 将.c文件放在包的实现该功能的目录中。当您运行go build时，它将被编译并链接到您的包中以及Go代码。

2. 如果函数在库中实现，则可以在Go文件中的import "C"语句之前的注释中使用the LDFLAGS directive。例如：

   // #cgo LDFLAGS: -lmylib
   import "C"