MinGW g++ 编译带静态变量的类时的问题,求高手解释一下！

打算建一个类，每生成一个对象就自动获取一个唯一的ID。

main.cpp

#include "stdio.h"

#include "CNode.h"

int main(int argc, char** argv)

{

CNode cNode1;

CNode cNode2;

CNode cNode3;

printf("cNode1.ID = %d\n ", cNode1.ulID);

printf("cNode2.ID = %d\n ", cNode2.ulID);

printf("cNode3.ID = %d\n ", cNode3.ulID);

}

CNode.h

#ifndef CNODE__

#define CNODE__

class CNode {

public:

CNode();

virtual ~CNode();

static unsigned int ulIDCreator;

unsigned int ulID;

};

unsigned int CNode::ulIDCreator = 0;

#endif

CNode.cpp

#include "CNode.h"

CNode::CNode(){

ulID = ++ulIDCreator;

}

CNode::~CNode(){

}

*** Internal Builder is used for build ****

g++ -O0 -g3 -Wall -c -fmessage-length=0 -osrc\CNode.o ..\src\CNode.cpp

g++ -oArctic.exe src\Main.o src\CNode.o

src\CNode.o: In function `ZN5CNodeC1Ev':

E:/EclipseWorkspace/Arctic/Debug/../src/CNode.cpp:9: multiple definition of `CNode::CNode()'

src\Main.o:E:/EclipseWorkspace/Arctic/Debug/../src/Main.cpp:13: first defined here

src\CNode.o: In function `ZN5CNodeD1Ev':

E:/EclipseWorkspace/Arctic/Debug/../src/CNode.cpp:13: multiple definition of `CNode::~CNode()'

src\Main.o:E:/EclipseWorkspace/Arctic/Debug/../src/Main.cpp:13: first defined here

src\CNode.o: In function `ZN5CNodeD0Ev':

E:/EclipseWorkspace/Arctic/Debug/../src/CNode.cpp:13: multiple definition of `CNode::~CNode()'

src\Main.o:E:/EclipseWorkspace/Arctic/Debug/../src/Main.cpp:13: first defined here

src\CNode.o: In function `ZN5CNodeC2Ev':

E:/EclipseWorkspace/Arctic/Debug/../src/CNode.cpp:9: multiple definition of `CNode::ulIDCreator'

src\Main.o:E:/EclipseWorkspace/Arctic/Debug/../src/Main.cpp:13: first defined here

collect2: ld returned 1 exit status

Build error occurred, build is stopped

Time consumed: 687 ms.

很奇怪的问题！怀疑是在不同文件中编译再连接在一块有问题。

于是去掉了CNode.cpp,只剩CNode.h。结果问题消失，

#ifndef CNODE__

#define CNODE__

class CNode {

public:

CNode(){ulID = ++ulIDCreator;};

virtual ~CNode(){};

static unsigned int ulIDCreator;

unsigned int ulID;

};

unsigned int CNode::ulIDCreator = 0;

#endif

console:

cNode1.ID = 1

cNode2.ID = 2

cNode3.ID = 3

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