作者Ygulu (生活以下)
看板C_and_CPP
標題[問題] 條件式編譯出問題嗎?
時間Fri Apr 3 02:05:11 2009
錯誤訊息
C:\Documents and Settings\Administrator\桌面\myC++>g++ -o test test.cpp
func.cpp
C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp/cc8qeaaa.o(.data+0x0):func.cpp: multiple
definition of `NS1::gain'
C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp/ccO0caaa.o(.data+0x0):test.cpp: first
defined here
C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp/cc8qeaaa.o(.data+0x8):func.cpp: multiple
definition of `NS2::gain'
C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp/ccO0caaa.o(.data+0x8):test.cpp: first
defined here
collect2: ld returned 1 exit status
first.h
#ifndef FIRST_H
#define FIRST_H
namespace NS1
{
double gain=5.9;
struct member
{
char *name;
int score;
};
double func(double);
}
#endif
second.h
#ifndef SECOND_H
#define SECOND_H
namespace NS2
{
double gain=2.6;
struct member
{
char *name;
int id;
};
double func(double);
}
#endif
func.cpp
#include "first.h"
#include "second.h"
double NS1::func(double x)
{
return x*NS1::gain;
}
double NS2::func(double y)
{
return y*NS2::gain;
}
test.cpp
#include <iostream>
using namespace std;
#include "first.h"
#include "second.h"
#include "first.h"
#include "second.h"
#include "first.h"
#include "second.h"
int main()
{
cout << "NS1::gain=" << NS1::gain << endl;
cout << "NS2::gain=" << NS2::gain << endl;
NS1::member john;
NS2::member david;
john.name="John";
john.score=53;
david.name="david";
david.id=8;
cout << (NS1::func(5.2)) << endl;
cout << (NS2::func(3.1)) << endl;
cout << john.name << " " << john.score << endl;
cout << david.name << " " << david.id << endl;
system("pause");
}
兩個.h檔我都有加#ifndef
為什麼還會出現multiple definition?
高手幫我解答一下吧 感謝
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◆ From: 114.42.216.102
1F：推 legnaleurc:extern 04/03 02:08
2F：→ Ygulu:不好意思 可以說詳細一點嗎 謝謝^^ 04/03 02:18
3F：→ adrianshum:在 h 只放 gain 的宣告, 把定義放回 cpp 04/03 10:14
4F：→ Ygulu:你是說在first.h裡面只寫double gain 不要寫=5.9嗎? 04/03 14:38
5F：推 legnaleurc:extern double gain; 04/03 15:02
6F：→ sbrhsieh:要學習 definition 與 declaration 的意義。 04/03 15:38