未定义的参考链接器错误 [英] Undefined reference linker error
问题描述
我制作了2个类，以制作单个链接列表MyHastList.h和MyHastList.cpp，其完美执行的代码如下！
---------- MyHashList.h ---------------------------------
I made 2 class to make a single linked list MyHastList.h and MyHastList.cpp and its working perfectly following is the code!!!!
----------MyHashList.h---------------------------------
#ifndef MYHASHLIST_H
#define MYHASHLIST_H
class MyHashListEntry{
public:
int key;
char* value;
MyHashListEntry* next;
MyHashListEntry(int keys,char* values);
};
class MyHashList{
public:
MyHashList();
~MyHashList();
void Append(int key,char* value);
void Prepend(int key,char* value);
char* FindValue(int key);
void Remove(int key);
bool IsEmpty();
void PrintHashList();
private:
MyHashListEntry* first;
MyHashListEntry* last;
};
#endif
--------------------- MyhashList.cpp -------------------------- -------
---------------------MyhashList.cpp---------------------------------
#include<iostream>
#include<conio.h>
#include "MyHashList.h"
using namespace std;
MyHashListEntry::MyHashListEntry(int keys,char* values){
key=keys; value=values; next=NULL;
}
MyHashList::MyHashList(){
first=last=NULL;
}
bool MyHashList::IsEmpty(){
if(first==NULL) return true; return false;
}
void MyHashList::Append(int key,char* value){
MyHashListEntry* element = new MyHashListEntry(key,value);
if(IsEmpty()) first=last=element;
else{
last->next=element;
last=element;
}
}
void MyHashList::Prepend(int key,char* value){
MyHashListEntry* element = new MyHashListEntry(key,value);
if(IsEmpty()) first=last=element;
else{
element->next=first;
first=element;
}
}
char* MyHashList::FindValue(int key){
if(IsEmpty()) return NULL;
MyHashListEntry* element=first;
if(first==last){
if(element->key==key) return element->value;
else return NULL;
}
else{
if(element->key==key) return element->value;
do{
element=element->next;
if(element->key==key) return element->value;
}while(element->next!=NULL);
}
return NULL;
}
void MyHashList::Remove(int key){
if(IsEmpty()) return;
MyHashListEntry* element=first;
if(first==last){
if(element->key==key) first=last=NULL;
}
else{
if(element){
if(element->key==key){
first=element->next;
delete element;
return;
}
}
for(element;element->next!=NULL;element=element->next){
MyHashListEntry* sub=element->next;
if(sub->key==key){
if(sub==last){
last=element;
last->next=NULL;
delete sub;
return;
}else{
element->next=sub->next;
delete sub;
return;
}
}
}
}
}
void MyHashList::PrintHashList(){
if(IsEmpty()) cout<<"NULL\n";
MyHashListEntry* element=first;
if(first==last){
cout<<"Key = "<<element->key<<" value = "<<element->value<<" \n";
}else{
cout<<"Key = "<<element->key<<" value = "<<element->value<<" \n";
do{
element=element->next;
cout<<"Key = "<<element->key<<" value = "<<element->value<<" \n";
}while(element->next!=NULL);
}
}
-------------------------------------------------- --------------------------
但是，当我尝试用它掩盖HashMAP时.代码显示链接器错误:
<>>>对``MyHashList :: MyHashList''的未定义引用
>>>>对``MyHashList :: Append''的未定义引用
等等..但是没有编译错误
以下是我的哈希映射类的代码:::
------------ MyHashTable.h -----------------------------
----------------------------------------------------------------------------
But When I tried to mask HashMAP with it. Code showed Linker error :
>>>>undefined reference to ''MyHashList::MyHashList''<<<<<<<<<<<<
>>>>undefined reference to ''MyHashList::Append''<<<<<<<<<<<<
so on.. but there was no compilation error
Following is the code for my Hash map class:::
------------MyHashTable.h-----------------------------
#ifndef MYHASHTABLE_H
#define MYHASHTABLE_H
#include "MyHashList.h"
class HashEntry{
public:
MyHashList* myList;
HashEntry();
};
class HashTable{
public:
HashTable(int size);
void Put(int key,char* value);
char* Get(int key);
private:
HashEntry** table;
int SIZE;
};
#endif
--------------- MyHashTable.cpp ---------------------
---------------MyHashTable.cpp---------------------
#include<iostream>
#include "MyHashTable.h"
using namespace std;
HashEntry::HashEntry(){
myList= new MyHashList();
}
HashTable::HashTable(int size){
SIZE=size;
table = new HashEntry*[SIZE];
for (int i = 0; i < SIZE; i++) table[i]=new HashEntry();
}
void HashTable::Put(int key,char* value){
table[key%SIZE]->myList->Append(key,value);
}
char* HashTable::Get(int key){
return ( table[key%SIZE]->myList->FindValue(key) );
}
请帮助::::::::::::::::::::::: ?????????????
Please help::::::::::::::::::::::: ?????????????
推荐答案
要记住的事情....
通常...
1)编译器始终更关注声明
还有
2)链接器始终关注定义.
类/函数的声明对于编译器来说是足够的....这就是为什么您的程序编译时没有任何错误.
因此，当您收到任何链接器错误时，原因可能是以下之一
1)您忘记将具有相应功能定义的CPP文件添加到项目中.
2)如果函数/类在另一个DLL中，则您可能忘记了从DLL中导出函数/类.
3)您可能正在链接到DLL的较早的lib文件.
Things to remember ....
Generally...
1 )Compiler is always more concerned about declarations
And
2 )Linker is always concerned about Definitions.
class/function Declaration is enough for compiler .... This is why your program is compiled without any error.
Hence when you get any linker error , the reason could be one of the following
1 ) You forgot to add CPP file with corresponding function definition to your project.
2 ) If the function/class is in another DLL, you might have forgot to export the function/class from DLL.
3 ) You might be linking to an older lib file of the DLL.
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