#include <iostream>
#include "my.h"
using namespace std;
using namespace myspace;
extern void output();
int main()
{
        output();
        return 0;
}

#include <iostream>
#include "my.h"
using namespace std;
using namespace myspace;
void output()
{
        cout << "verbose = " << verbose << endl;
}


#ifndef _MY_H
#define _MY_H
namespace myspace {
        bool verbose = true;
};
#endif


[xx@localhost cppwork]$ g++ a.cpp b.cpp
/tmp/ccRPtZqX.o:(.data+0x0): multiple definition of `myspace::verbose'
/tmp/ccgNbGeR.o:(.data+0x0): first defined here
collect2: ld returned 1 exit status
我想在a.cpp 和b.cpp中都使用verbose这个变量，但是出现冲突定义问题，请问如何解决，非常感谢！！

myspace::verbose

//test.cpp
#include <iostream>
#include "my.h"
using namespace std;
using namespace myspace;
extern void output();
int main()
{
        output();
        return 0;
}

//********************************
//my.h
#ifndef _MY_H
#define _MY_H
#include <iostream>
namespace myspace {
        bool verbose = true;
};
using namespace myspace;
using namespace std;
void output()
{
        cout << "verbose = " << verbose << endl;
}
#endif

#include <iostream>
#include "my.h"
using namespace std;
namespace myspace {                    //添加定义
        bool verbose = true;
};

using namespace myspace;
void output()
{
        cout << "verbose = " << verbose << endl;
}
************************************************************8
#ifndef _MY_H   //这里最好把_MY的_去掉，这样保险些
#define _MY_H
namespace myspace {                 //改成 namespace myspace{}；  头文件中因该用声明 不该定义  除了类，常量，和内联函数外
        bool verbose = true;
};
extern void output()；   //添加函数声明
#endif


[ 本帖最后由 yyblackyy 于 2010-4-2 18:27 编辑 ]

在main函数之前的那个#include "my.h"去掉