将 C 编译的静态库链接到 C++ 程序 [英] Linking C compiled static library to C++ Program

问题描述

我试图将一个静态库(用 gcc 编译)链接到一个 c++ 程序，但我得到了未定义的引用".我在 ubuntu 12.04 服务器机器上使用了 gcc 和 g++ 版本 4.6.3.例如，下面是阶乘法的简单库文件:

I tried to link a static library (compiled with gcc) to a c++ program and I got 'undefined reference'. I used gcc and g++ version 4.6.3 on a ubuntu 12.04 server machine. For example, here is the simple library file for factorial method:

mylib.h

#ifndef __MYLIB_H_
#define __MYLIB_H_

int factorial(int n);

#endif

mylib.c

#include "mylib.h"

int factorial(int n)
{
    return ((n>=1)?(n*factorial(n-1)):1);
}

我使用 gcc 为这个 mylib.c 创建了对象:

I created object for this mylib.c using gcc:

gcc -o mylib.o -c mylib.c

再次使用 AR 实用程序从目标文件创建静态库:

Again the static library was created from the object file using AR utility:

ar -cvq libfact.a mylib.o

我用 C 程序 (test.c) 和 C++ 程序 (test.cpp) 测试了这个库

I tested this library with a C program (test.c) and C++ program (test.cpp)

C 和 C++ 程序具有相同的主体:

Both C and C++ program have the same body:

#include "mylib.h"
int main()
{
    int fact = factorial(5);
    return 0;
}

假设静态库 libfact.a 在/home/test 目录中可用，我编译我的 C 程序没有任何问题:

Assuming static library libfact.a is available in /home/test directory, I compiled my C program without any issues:

gcc test.c -L/home/test -lfact

但是在测试 C++ 程序时，它抛出了一个链接错误:

However while testing C++ program, it threw a link error:

g++ test.cpp -L/home/test -lfact

test.cpp:(.text+0x2f): undefined reference to `factorial(int)'
collect2: ld returned 1 exit status

我什至尝试在 test.cpp 中添加 extern 命令:

I even tried adding extern command in test.cpp:

extern int factorial(int n) //added just before the main () function

还是同样的错误.

• 谁能告诉我这里哪里错了?
• 我在创建静态库时有什么遗漏吗?
• 我是否必须在我的 test.cpp 中添加任何内容才能使其正常工作?

• Can someone tell me what I am wrong here?
• Is there anything I missed while creating the static library?
• Do I have to add anything in my test.cpp to make it work?

推荐答案

问题是你没有告诉你的C++程序阶乘是用C写的.你需要改变你的test.h头文件.像这样

The problem is that you haven't told your C++ program that factorial is written in C. You need to change your test.h header file. Like this

#ifndef __MYLIB_H_
#define __MYLIB_H_

#ifdef __cplusplus
extern "C" {
#endif

int factorial(int n);

#ifdef __cplusplus
}
#endif

#endif

现在您的头文件应该适用于 C 和 C++ 程序.有关详细信息，请参阅此处.

Now your header file should work for both C and C++ programs. See here for details.

包含双下划线的 BTW 名称是为编译器保留的(以下划线和大写字母开头的名称也是如此)，因此严格来说 #ifndef __MYLIB_H_ 是非法的.我会改为 #ifndef MYLIB_H #define MYLIB_H

BTW names containing a double underscore are reserved for the compliler (so are names starting with an underscore and a capital letter) so #ifndef __MYLIB_H_ is illegal strictly speaking. I would change to #ifndef MYLIB_H #define MYLIB_H

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