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(使用gcc编译)链接到一个c ++程序,并得到'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factorial方法的简单库文件:
mylib.h
#ifndef __MYLIB_H_
#define __MYLIB_H_
int factorial(int n);
#endif
mylib.c
#includemylib.h
int factorial(int n)
{$ ((n> = 1)?(n *阶乘(n-1)):1);
}
我使用gcc创建了这个mylib.c的对象:
gcc -o mylib.o -c mylib.c
静态库也是使用AR实用程序从目标文件创建的:
ar -cvq libfact.a mylib.o
我用C程序(test.c)和C ++程序(test.cpp)
C和C ++程序都具有相同的主体:
#includemylib.h
int main()
{
int fact = factorial(5);
返回0;
$ / code>
假设静态库libfact.a在/ home / test目录中可用,I编译我的C程序没有任何问题:
pre $ gcc test.c -L / home / test -lfact
然而,在测试C ++程序时,它抛出一个链接错误:
g ++ test.cpp -L / home / test -lfact
test.cpp :(。text + 0x2f):undefined对`factorial(int)'的引用
collect2:ld返回1退出状态
我甚至尝试在test.cpp中添加extern命令:
extern int factorial(int n)//在main()函数之前添加
仍然是同样的错误。
- 有人可以告诉我我在这里犯了什么错误吗?静态库?
- 是否必须在我的
test.cpp
中添加任何内容才能使其工作?
问题是,您还没有告诉您的C ++程序使用C语言编写阶乘。您需要更改你的test.h头文件。像这样
#ifndef __MYLIB_H_
#define __MYLIB_H_
#ifdef __cplusplus
externC{
#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。详情请参阅以了解详情。
包含双下划线的BTW名称保留给编译器(所以名称以下划线和大写字母开头),所以 #ifndef __MYLIB_H _
严格地说是非法的。我会更改为 #ifndef MYLIB_H #define MYLIB_H
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);
}
I created object for this mylib.c using gcc:
gcc -o mylib.o -c mylib.c
Again the static library was created from the object file using AR utility:
ar -cvq libfact.a mylib.o
I tested this library with a C program (test.c) and C++ program (test.cpp)
Both C and C++ program have the same body:
#include "mylib.h"
int main()
{
int fact = factorial(5);
return 0;
}
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
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
I even tried adding extern command in test.cpp:
extern int factorial(int n) //added just before the main () function
Still the same error.
- 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?
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
Now your header file should work for both C and C++ programs. See here for details.
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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