'Class :: Class（function）'への未定義の参照

Question

他の類似の質問を検索し、ユーザーが提案したすべてを試しましたが、コンパイル時にこのエラーが発生します。私はC++の新機能で、stdリストクラスに新たに追加されました。私を助けてください。

私はこのコマンドを使用してリンクしようとしましたが、何も助けにはなりません。

g++ -std=c++11 tabledemo.cpp table.cpp entry.cpp -o tabledemo 

エラー：

/tmp/ccmZaWRt.o: In function `main': 
tabledemo.cpp:(.text+0x1eb): undefined reference to `Entry::access_count()' 
tabledemo.cpp:(.text+0x26f): undefined reference to `Entry::Entry(unsigned int, std::string)' 
tabledemo.cpp:(.text+0x2be): undefined reference to `operator>>(std::istream&, Entry&)' 
tabledemo.cpp:(.text+0x2cd): undefined reference to `Entry::get_key() const'  
tabledemo.cpp:(.text+0x46b): undefined reference to `Entry::access_count()'  
tabledemo.cpp:(.text+0x4cf): undefined reference to `Entry::access_count()' 
/tmp/ccmZaWRt.o: In function `user_get(Table&)': 
tabledemo.cpp:(.text+0x6d8):undefined reference to `Entry::access_count()' 
tabledemo.cpp:(.text+0x74a):undefined reference to `Entry::access_count()' 
/tmp/ccmZaWRt.o: In function user_remove(Table&)': 
tabledemo.cpp:(.text+0x7d8): undefined reference to `Entry::access_count()' 
/tmp/ccmZaWRt.o:tabledemo.cpp:(.text+0x849): more undefined references to `Entry::access_count()' follow 
/tmp/ccjPftPu.o: In function 
`Table::Table(unsigned int, std::istream&)': table.cpp:(.text+0x187):  undefined reference to `Entry::Entry(unsigned int, std::string)' 
table.cpp: (.text+0x1b2): undefined reference to `operator>>(std::istream&, Entry&)'  
/tmp/ccjPftPu.o: In function `Table::put(unsigned int, std::string)': 
table.cpp:(.text+0x298): undefined reference to `Entry::Entry(unsigned int, std::string)'  
table.cpp:(.text+0x337): undefined reference to `Entry::get_key() const' 
table.cpp:(.text+0x372): undefined reference to `Entry::set_data(std::string)' 
/tmp/ccjPftPu.o: In function `Table::put(Entry)': 
table.cpp:(.text+0x40d): undefined reference to `Entry::get_key() const' 
table.cpp:(.text+0x4a3): undefined reference to `Entry::get_key() const' 
table.cpp:(.text+0x4b9): undefined reference to `Entry::get_key() const' 
/tmp/ccjPftPu.o: In function `Table::get(unsigned int) const': 
table.cpp:(.text+0x5ee): undefined reference to `Entry::get_key() const' 
table.cpp:(.text+0x60b): undefined reference to `Entry::get_data() const' 
/tmp/ccjPftPu.o: In function `Table::remove(unsigned int)': 
table.cpp:(.text+0x6f2): undefined reference to `Entry::get_key() const' 
/tmp/ccjPftPu.o: In function `operator<<(std::ostream&, Table const&)': 
table.cpp:(.text+0x90b): undefined reference to `operator<<(std::ostream&, Entry&)' 
/tmp/ccjPftPu.o: In function `std::list<Entry,std::allocator<Entry>::remove(Entry const&)': 
table.cpp:(.text._ZNSt4listI5EntrySaIS0_EE6removeERKS0_[_ZNSt4listI5EntrySaIS0_EE6removeERKS0_]+0x78): undefined reference to `Entry::operator unsigned int() const' 
table.cpp:(.text._ZNSt4listI5EntrySaIS0_EE6removeERKS0_[_ZNSt4listI5EntrySaIS0_EE6removeERKS0_]+0x86): undefined reference to `Entry::operator unsigned int() const' 
/tmp/ccjPftPu.o: In function `std::list<Entry, std::allocator<Entry> 
::merge(std::list<Entry, std::allocator<Entry> >&&)': 
table.cpp:(.text._ZNSt4listI5EntrySaIS0_EE5mergeEOS2_[_ZNSt4listI5EntrySaIS0_EE5mergeEOS2_]+0xc0): undefined reference to `Entry::operator unsigned int() const' 
table.cpp:(.text._ZNSt4listI5EntrySaIS0_EE5mergeEOS2_[_ZNSt4listI5EntrySaIS0_EE5mergeEOS2_]+0xd6): undefined reference to `Entry::operator unsigned int() const' collect2: 
error: ld returned 1 exit status 

ENTRY.H

#ifndef ENTRY_H 
#define ENTRY_H 

#include <string> 
#include <iosfwd> 

class Entry { 

public: 
// constructor 
Entry(unsigned int key = 0, std::string data = ""); 

// access and mutator functions 
unsigned int get_key() const; 
std::string get_data() const; 
static unsigned int access_count(); 
void set_key(unsigned int k); 
void set_data(std::string d); 

// operator conversion function simplifies comparisons 
operator unsigned int() const; 

// input and output friends 
friend std::istream& operator>> 
    (std::istream& inp, Entry &e); 
friend std::ostream& operator<< 
    (std::ostream& out, Entry &e); 

private: 
unsigned int key; 
std::string data; 
static unsigned int accesses; 
}; 

#endif 

ENTRY.CPP

#include "entry.h" 
#include <iostream> 
using namespace std; 

unsigned int Entry::accesses = 0; 

Entry::Entry(unsigned int key, std::string data) 
: key(key), data(data) { } 

unsigned int Entry::get_key() const 
{ ++accesses; return key; } 

std::string Entry::get_data() const 
{ return data; } 

unsigned int Entry::access_count() 
{ return accesses; } 

void Entry::set_key(unsigned int k) 
{ key = k; } 

void Entry::set_data(std::string d) 
{ data = d; } 

Entry::operator unsigned int() const 
{ return get_key(); } 

istream& operator>> (istream& inp, Entry &e) { 
    inp >> e.key; 
// get data in two parts to handle white space 
string first_word, rest_of_line; 
inp >> first_word; 
getline(inp, rest_of_line); 
e.data = first_word + rest_of_line; 
return inp; 
} 

ostream& operator<< (ostream& out, Entry &e) { 
    out << e.get_key() << ": " << e.get_data(); 
    return out; 
} 

TABLE.H

#ifndef TABLE_H 
#define TABLE_H 

#include "entry.h" 
#include <string> 
#include <iosfwd> 
#include <list> 


class Table { 

public: 

//constructors                       
Table(unsigned int max_entries = 100); 
Table(unsigned int entries, std::istream &input); 

void put(unsigned int key, std::string data); 
void put(Entry e); 

std::string get(unsigned int key) const; 
bool remove(unsigned int key); 
int hashkey(int key) const; 

friend std::ostream& operator<< (std::ostream &out, const Table &t); 

private: 

unsigned int tablesize; 
unsigned int entrycount; 
std::list<Entry>* chainedarray; 

}; 

#endif 

TABLE.CPP

#include "table.h" 
#include "entry.h" 
#include <string> 
#include <list> 
#include <iostream> 
#include <fstream> 

using namespace std; 

Table::Table(unsigned int max_entries) { 
    tablesize = max_entries*2; 
    entrycount = 0; 
    chainedarray = new list<Entry>[tablesize]; 

} 

Table::Table(unsigned int entries, std::istream &input){ 

    tablesize = entries * 2; 
    chainedarray = new list<Entry>[tablesize]; 
    entrycount = entries; 

for(int i = 0; i < entries; i++){ 
    Entry t; 
    input >> t; 
    put(t); 
} 
} 

void Table::put(unsigned int key, std::string data){ 
    Entry newentry(key, data); 
list<Entry>::iterator it; 
    //int ifnoupdate = 1;                      
    for(it = chainedarray[hashkey(key)].begin(); it !=  chainedarray[hashkey(key)].end(); it++){ 
    if(it->get_key() == key){ 
     // ifnoupdate = 0;                     
     it->set_data(data); 
    } 
} 
    // if (ifnoupdate == 1) {chainedarray[hashkey(key)].push_back(newE);entrycount++;}      
} 

void Table::put(Entry e){ 
    int key = hashkey(e.get_key()); 
    for (std::list<Entry>::iterator it = chainedarray[hashkey(key)].begin(); it != chainedarray[hashkey(key)].end(); ++it){ 
    if (e.get_key() == it->get_key()){ 
     chainedarray[hashkey(key)].remove(*it); 
    } 
    chainedarray[hashkey(key)].push_back(e); 
    } 
} 

std::string Table::get(unsigned int key) const{ 
    int place = hashkey(key); 
    for(Entry temp: chainedarray[place]){ 
    if (key==temp.get_key()){ 
     return temp.get_data(); 
    } 
    else return std::string(); 
    } 

} 

bool Table::remove(unsigned int key){ 
int place = hashkey(key); 
for (Entry t : chainedarray[place]){ 
    if(t.get_key() == key){ 
     chainedarray[place].remove(t); 
     entrycount--; 
     return true; 
    } 
    } 
    return false; 
} 

std::ostream& operator<< (std::ostream &out, const Table &t){ 
    list<Entry> plist; 
    for (int i = 0; i < t.entrycount; i++){ 
    for (Entry p : t.chainedarray[i]){ 
     plist.push_back(p); 
    } 
    } 
    plist.sort(); 
    for (Entry p : plist){ 
    out << p << endl; 
    } 
    return out; 
} 

int Table::hashkey(int key) const { 
    return key % tablesize; 
} 

TABLEDEMO.CPP

#include <iostream> 
#include <fstream> 
#include "table.h" 
#include "entry.h" 
using namespace std; 

unsigned int user_get(Table &t); 
unsigned int user_remove(Table &t); 

int main() { 

cout << "Demonstrate very small table\n"; 
Table t(5); 
t.put(7, "seven"); 
t.put(9, "nine"); 
t.put(17, "Seventeen"); 
t.put(4, "four"); 
t.put(36, "Thirty-six"); 
cout << t; 
cout << "key accesses: " << Entry::access_count() << endl; 

cout << "\nNow demonstrate default size table\n"; 
Table t2; 
Entry e; 
unsigned int count = 0; 
cout << "Enter up to 100 entries for a new table.\n" 
    << "(enter 0 key and random data to quit)\n"; 
do { 
    cin >> e; 
    if (e.get_key() == 0) break; 
    t2.put(e); 
    ++count; 
} while(count < 100); 
cout << t2; 
cout << "Try removing some entries (enter 0 to quit)\n"; 
while (user_remove(t2) != 0) 
    ; 
cout << t2; 

cout << "\nFinally demonstrate larger table\n"; 
ifstream input; 
input.open("fips.txt"); 
if (!input.good()) { 
    cout << "No fips.txt in current directory. Quitting\n"; 
    return 1; 
} 
Table t3(3142, input); 
cout << "Try getting some entries by FIPS code keys\n" 
    << "(enter 0 key to quit)\n"; 
while (user_get(t3) != 0) 
    ; 
cout << "Print large table to sortedfips.txt?\n"; 
char ans; 
cin >> ans; 
if (ans == 'Y' || ans == 'y') { 
    unsigned int start = Entry::access_count(); 
    ofstream out; 
    out.open("sortedfips.txt"); 
    out << t3; 
    out.close(); 
    cout << "done writing to sortedfips.txt ... required " 
     << Entry::access_count() - start << " accesses\n"; 
} 
return 0; 
} 

unsigned int user_get(Table &t) { 
    unsigned int key; 
    cout << "Enter key to get:\n"; 
    cin >> key; 
    if (key != 0) { 
     unsigned int start = Entry::access_count(); 
     cout << "data at key " << key << ": " << t.get(key) << endl; 
     cout << "(accesses: " << 
      Entry::access_count() - start << ")\n"; 
    } 
    return key; 
} 

unsigned int user_remove(Table &t) { 
    unsigned int key; 
    cout << "Enter key to remove:\n"; 
    cin >> key; 
    if (key != 0) { 
     unsigned int start = Entry::access_count(); 
     if (t.remove(key)) 
      cout << "removed key: " << key << endl; 
     else 
      cout << "did not find key: " << key << endl; 
     cout << "(accesses: " 
      << Entry::access_count() - start << ")\n"; 
    } 
    return key; 
} 

Answer 1

static unsigned int access_count();は正確には何ですか？

static unsigned int access_countがメソッドの場合は、宣言されているため、このメソッドが実装されていないため、実装する必要があります。

ので、このエラーが発生します。undefined references to Entry::access_count()

static unsigned int access_countは、クラスのメンバ変数であるならば、あなたはほとんどのコンストラクタの最初のためにそれに値を与えます。

Answer 2

g++ -std=c++11 tabledemo.cpp table.h entry.h -o table demo 

あなたはヘッダをコンパイルすべきではない、とあなたは3つの無関係なファイルを投稿しますが、 `entry.cpp`を残してなぜあなたはentry.cppとtable.cpp

g++ -std=c++11 tabledemo.cpp table.cpp entry.cpp -o table_demo