带有C和C ++混合代码的Makefile [英] Makefile with mixed c and C++ code
问题描述
我正在尝试在编译.c和.cpp文件以在Ubuntu上创建应用程序方面做一些非常简单的事情.我创建了一个Makefile,但是它失败,并出现以下错误.
I'm trying to do something pretty simple in compiling .c and .cpp files to create an application on Ubuntu. I created a Makefile but it fails with the following error.
~/code/test$ make
gcc -Wall -c test1.c -o test1.o
g++ -c -Wall -D__STDC_LIMIT_MACROS main.cpp -o main.o
g++ -c -Wall -D__STDC_LIMIT_MACROS class_a.cpp -o class_a.o
echo g++ test1.o main.o class_a.o -o myapp
g++ test1.o main.o class_a.o -o myapp
g++ test1.o main.o class_a.o -o myapp
main.o: In function `main':
main.cpp:(.text+0x21): undefined reference to `add(int, int)'
collect2: error: ld returned 1 exit status
make: *** [myapp] Error 1
main.cpp如下
main.cpp is as follows
#include "stdio.h"
#include "test1.h"
#include "class_a.h"
int main(int argc , char **argv)
{
int c = 0;
c = add(10, 15);
A a;
a.addToA(c);
printf("result = %d\n",c);
}
test1.h
#ifndef _FILE_H
#define _FILE_H
int add(int a, int b);
#endif
test1.c
#include "test1.h"
int add(int a, int b)
{
return a + b;
}
class_a.h
class_a.h
#ifndef _class_A_H
#define _class_A_H
class A
{
public:
A();
int addToA(int c);
private:
int a;
};
#endif // _class_A_H
class_a.cpp
class_a.cpp
#include "class_a.h"
A::A()
{
a = 0;
}
int
A::addToA(int c)
{
a += c;
return a;
}
Makefile
CXX = g++
CC = gcc
CFLAGS = -Wall -c
CXXFLAGS = -c -Wall -D__STDC_LIMIT_MACROS
CSOURCES=test1.c
CPPSOURCES= main.cpp \
class_a.cpp
COBJECTS=$(CSOURCES:.c=.o)
CPPOBJECTS = $(CPPSOURCES:.cpp=.o)
EXECUTABLE=myapp
all: $(EXECUTABLE)
$(EXECUTABLE): $(COBJECTS) $(CPPOBJECTS)
echo $(CXX) $(COBJECTS) $(CPPOBJECTS) -o $@
$(CXX) $(COBJECTS) $(CPPOBJECTS)-o $@
.c.o:
$(CC) $(CFLAGS) $< -o $@
.cpp.o:
$(CXX) $(CXXFLAGS) $< -o $@
clean:
rm -rf $(COBJECTS)
rm -rf $(CPPOBJECTS)
rm -rf $(EXECUTABLE)
推荐答案
要能够从C ++调用C函数(或从C调用C ++函数),必须防止C ++名称混乱,以便链接程序正常工作.
To be able to call C functions from C++ (or C++ functions from C) you have to prevent the C++ name mangling, so that the linker will work properly.
也就是说,C函数int add(int, int)
实际上在目标文件add
中生成一个符号.但是C ++函数int add(int, int)
将生成一个名为_Z3addii
的符号.那些将不会链接.
That is, C function int add(int, int)
actually generates a symbol in the object file called add
. But a C++ function int add(int, int)
will generate a symbol named _Z3addii
. And those will not link.
解决方案:使用C ++编译时,混合语言函数应声明为extern "C"
.不幸的是,extern "C"
声明在C中不存在,仅在C ++中存在.
Solution: the mixed language functions, when compiled in with C++ should be declared extern "C"
. Unfortunately the extern "C"
declaration does not exist in C, only in C++.
所以标准成语是:
#ifndef _FILE_H
#define _FILE_H
#ifdef __cplusplus
extern "C" {
#endif
int add(int a, int b);
#ifdef __cplusplus
} //extern "C"
#endif
#endif
那样,C代码与以前一样,但是C ++代码将使用未修饰的名称查找add
函数,并且所有这些都将链接在一起.
That way, the C code is just as before, but the C++ code will look for the add
function using the undecoraded name, and all will link together.
这篇关于带有C和C ++混合代码的Makefile的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!