Question

我想从C函数空间调用go func，但程序会抛出构建错误。

example.go

package main

/*
#include "test.c"
*/
import "C"
import "fmt"

func Example() {
    fmt.Println("this is go")
    fmt.Println(C.GoString(C.myprint(C.CString("go!!"))))
}

// export receiveC              (remove the extra space between // and export)
func receiveC(msg *C.char) {
    fmt.Println(C.GoString(msg))
}

func main() {
    Example()
}

test.c的

#include <stdio.h>

extern void receiveC(char *msg);

char* myprint(char *msg) {
    receiveC(msg);  // calling the exported go function
    return msg;     
    }

当我执行命令来运行/ build（go build或go run example.go或go build example.go）程序时，它会抛出错误：

# github.com/subh007/goodl/cgo
Undefined symbols for architecture x86_64:
  "_receiveC", referenced from:
      _myprint in example.cgo2.o
      __cgo_6037ec60b2ba_Cfunc_myprint in example.cgo2.o
      _myprint in test.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

我正在跟随cgo slides编写程序。如果有任何错误，请告诉我。

Edit1：我使用的是OS-X 10.9操作系统。

EDIT2：我在// export之间有一个额外的空格，//和export之间不应有空格。但是现在我在构建时遇到以下错误：

# github.com/subh007/goodl/cgo
duplicate symbol _myprint in:
    $WORK/github.com/subh007/goodl/cgo/_obj/_cgo_export.o
    $WORK/github.com/subh007/goodl/cgo/_obj/example.cgo2.o
duplicate symbol _receiver_go in:
    $WORK/github.com/subh007/goodl/cgo/_obj/_cgo_export.o
    $WORK/github.com/subh007/goodl/cgo/_obj/example.cgo2.o
duplicate symbol _myprint in:
    $WORK/github.com/subh007/goodl/cgo/_obj/_cgo_export.o
    $WORK/github.com/subh007/goodl/cgo/_obj/test.o
duplicate symbol _receiver_go in:
    $WORK/github.com/subh007/goodl/cgo/_obj/_cgo_export.o
    $WORK/github.com/subh007/goodl/cgo/_obj/test.o
ld: 4 duplicate symbols for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Answer 1

生成重复的符号，因为我已将test.c直接包含在go文件中。因此符号包括两次。

我认为，编写此代码的正确方法是（如果我错了请评论）：

定义头文件（test.h）：

#ifndef TEST_H_
#define TEST_H_

char* myprint(char *msg);

#endif

定义实现文件（test.c）：

 #include <stdio.h>
 #include "test.h"

 extern void receiveC(char *msg);

 char* myprint(char *msg) {
     receiveC(msg);
     return msg;
  }

将.h文件包含在go文件中（example.go）：包主要

 /*
 #include "test.h"
 */
 import "C"
 import "fmt"

 func Example() {
      fmt.Println("this is go")
      fmt.Println(C.GoString(C.myprint(C.CString("go!!"))))
  }

  // make sure that there should be no space between the `//` and `export`
  //export receiveC
  func receiveC(msg *C.char) {
        fmt.Println(C.GoString(msg))
  }

  func main() {
       Example()
  }

构建程序：
```
 go build
```
运行生成的可执行文件（使用cgo名称生成可执行文件，需要一些调查才能找到原因）。
```
 $./cgo
```

cgo：体系结构x86_64的未定义符号

1 个答案: