vc++6.0 类中定义 static 变量报错

来源：互联网发布：守望先锋看数据编辑：程序博客网时间：2024/06/04 18:49

在实验《提高C++性能的编程技术》中第一个源代码是遇到了报错。。。。。

自己补全了点代码：

#pragma once#include <iostream>#include <string>using namespace std;class Trace{public:Trace(const string &name);~Trace();void debug(const string &msg);static bool traceIsActive;static int t;private:string theFunctionName;};

#include "Trace.h"Trace::Trace(const string &name):theFunctionName(name){if(traceIsActive){cout<<"Enter function"<<name<<endl;}}inline void Trace::debug(const string &msg){if(traceIsActive){cout<<msg<<endl;}}Trace::~Trace(){if(traceIsActive){cout<<"Exit function"<<theFunctionName<<endl;}}

#include <windows.h>#include <iostream>#include "Trace.h"using namespace std;int addOne( int x){

return x+1;}int main(){Trace::traceIsActive = false;int j=1000000,y;SYSTEMTIME t1,t2;GetSystemTime(&t1);for(int i=0 ; i< j ; i++){y = addOne(i);}GetSystemTime(& t2);cout<<t2.wSecond*1000+t2.wMilliseconds-t1.wSecond*1000-t1.wMilliseconds<<endl;return 0;}

上边的代码会报如下错误：mian.obj : error LNK2001: unresolved external symbol "public: static bool Trace::traceIsActive" (?traceIsActive@Trace@@2_NA)Trace.obj : error LNK2001: unresolved external symbol "public: static bool Trace::traceIsActive" (?traceIsActive@Trace@@2_NA)Debug/1_1.exe : fatal error LNK1120: 1 unresolved externals执行 link.exe 时出错.我在百度了好久找的答案是在Trace.cpp文件中加入 bool Trace::traceIsActive ;修改后源文件为：

#include "Trace。好“
bool Trace::traceIsActive ;//新增加的行
Trace::Trace(const string &name):theFunctionName(name){ if(traceIsActive) {  cout<<"Enter function"<<name<<endl; }}

........

虽然可以编译通过了，不过我还想知道具体的原因，先谢过了

关于static变量的详细请看我的新帖http://blog.csdn.net/xt0916020331/article/details/7530195 说的不当之处请指出