[英]compiling c and c++ files using g++
I am trying to compile a C and C++ file and link them together. 我正在尝试编译C和C ++文件并将它们链接在一起。 I am following the answers from this link - Compiling C and C++ files together using GCC 我正在关注此链接的答案- 使用GCC一起编译C和C ++文件
However I have a different problem, which is not explained in that post. 但是,我有一个不同的问题,该职位未对此进行解释。 I have defined my main() in the C++ file and using a function whose details are there in the C file. 我已经在C ++文件中定义了main(),并使用了一个函数,其详细信息在C文件中。 The declaration of the function is there in a .h file, which is included both in the C and C++ file. 函数的声明在.h文件中,该文件同时包含在C和C ++文件中。
My C++ file - 我的C ++文件-
#include<iostream>
#include<testc.h>
using namespace std;
extern "C" void cfunc(int, int);
int main()
{
cout<<"Hello from cpp"<<endl;
cfunc(3,6);
}
My C file - 我的C档案-
#include<stdio.h>
#include<testc.h>
int cfunc2(int a, int b)
{
return a+b;
}
void cfunc(int a, int b)
{
printf("Hello from c %d\n",cfunc2(a,b));
}
My .h file - 我的.h文件-
int cfunc2(int, int);
void cfunc(int, int);
As per other posts if I use a C function in my C++ code, I need to give the following definition in my C++ file - 与其他帖子一样,如果我在C ++代码中使用C函数,则需要在C ++文件中提供以下定义-
extern "C" void cfunc(int, int);
However when I run like this I get the following error - 但是,当我这样运行时,出现以下错误-
testcpp.cpp:6:17: error: conflicting declaration of ‘void cfunc(int, int)’ with ‘C’ linkage
extern "C" void cfunc(int, int);
In file included from testcpp.cpp:2:0:
inc/testc.h:9:6: note: previous declaration with ‘C++’ linkage
void cfunc(int, int);
testcpp.cpp is where I make the call from main, testc.c contains the function definition and testc.h is the header file. 我从main进行调用的地方是testcpp.cpp,testc.c包含函数定义,而testc.h是头文件。
I run the following set of commands - 我运行以下命令集-
gcc -c -std=c99 -o testc.o testc.c -Iinc
g++ -c -std=c++0x -o testcpp.o testcpp.cpp -Iinc
g++ -o myapp testc.o testcpp.o
The inc folder contains the .h file inc文件夹包含.h文件
Anything I am doing wrong? 我做错了什么?
You do not need to provide another declaration of the function in the C++ file after you declared it in the .h
file (and included this file from the C++, as it appears). 在.h
文件中声明了该函数之后,无需在C ++文件中提供该函数的另一声明(并且此文件从C ++中包含了,出现了)。 This is what the C++ compiler clearly complains about, as they are different. 这是C ++编译器明显抱怨的地方,因为它们是不同的。
Instead, either wrap you declaration inside the .h
file like the following: 而是将声明包装在.h
文件中,如下所示:
#ifdef __cplusplus
extern "C" {
#endif
< your declarations go here >
#ifdef __cplusplus
}
#endif
OR wrap the #include
line in the same way in the .cpp
file: 或以相同方式将#include
行包装到.cpp
文件中:
extern "C" {
#include "testc.h"
}
The idea is that the C and C++ parts will need to see the same function declared in a different way. 这个想法是C和C ++部分将需要看到以不同方式声明的同一函数。 That's why #ifdef
is needed inside the .h
file, as it is included from both C and C++. 这就是为什么.h
文件中需要#ifdef
的原因,因为C和C ++都包含了该文件。
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