go - cgo：架构 x86_64 的未定义符号

Question

我想从 C 函数空间调用 go func，但程序抛出构建错误。

例子.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()
}

测试.c

#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/构建（go build或go run example.go或go build example.go）程序时，它会引发错误：

# 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)

我正在按照cgo 幻灯片编写程序。请让我知道这里的任何错误。

Edit1：我使用的是 OS-X 10.9 操作系统。

Edit2：之间有一个额外的空格，和之间// export应该没有空格。但是现在我在构建时收到以下错误：//export

# 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)

score 4 · Accepted Answer

生成重复符号是因为我已将其test.c直接包含到 go 文件中。所以符号被包含了两次。

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;
   }

将文件包含.h到go文件 (example.go) 中：

  package main
  /*
  #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名称生成的可执行文件，需要一些调查才能找到原因）。
```
  $./cgo
```

go - cgo：架构 x86_64 的未定义符号

1 回答 1

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