class.h
#include <iostream>
#include <stdint.h>
using namespace std;
template <typename T>
class CIntegerType {
public:
void Show ( void );
private:
T m_Data;
};
class.cpp
#include "class.h"
template <typename T>
void CIntegerType<T> :: Show ( void ) {
cout << m_Data << endl;
}
main.cpp
#include "class.h"
int main ( void ) {
CIntegerType<uint32_t> UINT32;
UINT32 . Show ();
return 0;
}
This commands return:
g++ -Wall -pedantic -c main.cpp
g++ -Wall -pedantic -c class.cpp
g++ -Wall -pedantic -o class.o main.o
main.o: In function `main':
main.cpp:(.text+0x11): undefined reference to 'CIntegerType< unsigned int>::Show()'
collect2: ld returned 1 exit status
Try putting your template implementation in the header file.
See: Why can templates only be implemented in the header file?
Try g++ -Wall -pedantic -o main.o class.o instead. You are facing the same problem as in this question: g++ linking order dependency when linking c code to c++ code
The linker searches for functions in the order they appear. Since you have a template function, its use in main must be fed to the linker prior to the actual code to instantiate it in class.
Related
The code examples explain the problem fairly straightforward:
Hash.h
#include <iostream>
#include <cstdint>
using namespace std;
class Hash {
public:
Hash(int64_t sz);
int64_t size;
};
Hash.cpp
#include "Hash.h"
using namespace std;
Hash::Hash(int64_t sz) : size(sz)
{
cout << "Hash int" << endl;
}
main.cpp
#include "Hash.h"
using namespace std;
int main(int argc, char *argv[])
{
Hash HashTable(12);
return 0;
}
And here is the version file, foo.map:
VER_0.1
{
global:
extern "C++" {
"Hash::Hash(int64_t)";
};
local:
*;
};
For the compilation:
$g++ -g -c -Wall -Werror -fpic Hash.cpp -std=c++0x
$g++ -shared -o Hash.so Hash.o -std=c++0x -Wl,--version-script=foo.map
$g++ -g -o prog Hash.so main.cpp -std=c++0x
The error message:
/tmp/ccd60Ulm.o: In function `main':
/remote/ltg_engine1_us03/liangwa/test/004/main.cpp:7: undefined reference to `Hash::Hash(long)'
collect2: error: ld returned 1 exit status
Then if I change all int64_t to int or long, it compiles fine. So anything special with int64_t? I am using g++ 7.3.0
i have this simple code in the following files:
Stat.h
#ifndef STAT_H
#define STAT_H
class Stat {
public:
void compute_value();
};
#endif
Stat.cpp
class Stat {
public:
void compute_value() {
}
};
main.cpp
#include "Stat.h"
int main(void)
{
Stat stat;
stat.compute_value();
}
When i try to compile i got the following error:
clang++ -std=c++14 -Wall -Wextra -pedantic -Weverything -O3 Stat.cpp main.cpp -o main
/tmp/main-0466d7.o: In function `main':
main.cpp:(.text+0xf6a): undefined reference to `Stat::compute_value()'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
You are redefining the class in your Stat.cpp source file because definition is also a declaration. Instead of having the entire class redefinition you only need to define the member function(s) in your Stat.cpp source file and include the Stat.h header:
#include "Stat.h"
void Stat::compute_value() {}
I've got a problem when declaring a class in a separate object file and then using it in the main function of another file:
main.cpp:
#include <helloclass.hpp>
using namespace std;
int main() {
Hello hi;
hi.hello();
return 0;
}
helloclass.cpp:
#include <iostream>
using namespace std;
class Hello {
public:
void hello() {
cout << "Hello world\n";
}
Hello() {}
};
helloclass.hpp:
class Hello {
public:
void hello();
Hello();
};
Then I ran the following commands:
g++ -I. -c main.cpp
g++ -c helloclass.cpp
g++ -o main main.o helloclass.o
However, the last command gives the following output:
main.o: In function `main':
main.cpp:(.text+0x1f): undefined reference to `Hello::Hello()'
main.cpp:(.text+0x2b): undefined reference to `Hello::hello()'
collect2: error: ld returned 1 exit status
To me, it seems like I'm missing something pretty obvious. Does anyone know how to fix this?
You should not redefine the class in the separate source file. Instead include the header-file and implement the Hello::hello function (and the Hello::Hello constructor).
Consider a program consists of files AA.hpp, A1.hpp, A1.cpp, and main.cpp compiled with g++ -std=c++11 main.cpp A1.cpp.
// file AA.hpp
template < int > struct AA;
// file A1.hpp
#include "AA.hpp"
template <> struct AA<1> { /*implementation goes here...*/ };
extern template struct AA<1>;
// file A1.cpp
#include "A1.hpp"
template struct AA<1>;
// file main.cpp
#include "A1.hpp"
int main()
{
AA<1> a1;
// use a1 ...
return 0;
}
Compare this with a scenario when there is no A1.cpp and there is no explicit instantiation declaration in A1.hpp. Will I get any compilation time benefits in the first scenario? And why?
Another question. What if I make a shared library of A1.cpp by g++ -std=c++11 -shared -o libA1.so A1.cpp and then make executable with g++ -std=c++11 -lA1 main.cpp? Will the calls of A1's functions in man.cpp refer to the code in libA1.so or they will be generated (inlined or not) in the executable?
i been having a problem that i tried for many days to fix but i cant find a solution for it.
I keep getting this Error:
undefined reference to 'Simulator::Simulator(int, int)'
undefined reference to 'Simulator::run();'
undefined reference to 'Simulator::~Simulator()'
undefined reference to 'Simulator::~Simulator()'
I searched for an answer but nothing seems to be working for me.
Here are my classes:
main.cpp:
#include <iostream>
#include <cstdlib>
#include "Simulator.h"
int main(int argc, char** argv) {
//Some code
Simulator sim(rows, cols);
sim.run();
}
Simulator.h:
#include <iostream>
#include "PersonQueue.h"
#include "DogQueue.h"
class Simulator {
void drawBoard();
DogQueue _dq;
PersonQueue _pq;
public:
int dog_num, person_num;//Number of entitys
int _rows, _cols;//Should be static but wont work.
void fill_queue();//check
void init_clrs();
Simulator(int rows, int cols);//check
void run();//check
~Simulator();
};
Simulator.cpp:
#ifndef SIM_C
#define SIM_C
#include <iostream>
#include <curses.h>
#include "Simulator.h"
int Simulator:: _rows;
int Simulator:: _cols;
Simulator::Simulator(int row, int col) {
_rows = row;
_cols = col;
dog_num = 2; //number of dog entitys
person_num = 2;//number of person entitys
}
void Simulator::init_clrs() {
//some code...
}
void Simulator::drawBoard() {
//some code...
}
void Simulator::fill_queue() {
//some code...
}
void Simulator::run() {
initscr();
start_color();
Simulator::init_clrs();
Simulator::fill_queue();
Simulator::drawBoard();
while (std::cin.get() != (char)27) {
Person* person_obj = _pq.dequeue();
Dog* dog_obj = _dq.dequeue();
person_obj->Person::advance();
dog_obj->Dog::advance();
if (dog_obj->steps == MAX_STEP && person_obj->steps) {
_dq.enqueue(dog_obj);
_pq.enqueue(person_obj);
}
refresh();
}
}
Simulator::~Simulator() {//To_be_changed
delete this;
}
#endif
From what i read i believe the problem may be with the makefile but it seems ok and works until i get the undefined error.
makefile just in case:
tester: main.o simulator.o personqueue.o dogqueue.o character.o person.o dog.o
g++ -Wall main.cpp -lncurses -o tester
main.o: main.cpp
g++ -c -Wall main.cpp -o main.o
simulator.o: Simulator.cpp Simulator.h
g++ -c -Wall Simulator.cpp Simulator.h -o simulator.o
character.o: Character.cpp Character.h
g++ -c -Wall Character.cpp Character.h -o character.o
person.o: Person.cpp Person.h
g++ -c -Wall Person.cpp Person.h -o person.o
dog.o: Dog.cpp Dog.h
g++ -c -Wall Dog.cpp Dog.h -o dog.o
personqueue.o: PersonQueue.cpp PersonQueue.h
g++ -c -Wall PersonQueue.cpp PersonQueue.h -o personqueue.o
dogqueue.o: DogQueue.cpp DogQueue.h
g++ -c -Wall DogQueue.cpp DogQueue.h -o dogqueue.o
clean:
rm -rf *.o tester
Thank you for any input on this issue.
EDIT:
I dont believe the problem is with DogQueue or Person queue as all they include is Dog.h Person.h
but anyways just to be sure:
#include "DogQueue.h"
#include <cstdlib>
//Some code...
#include "PersonQueue.h"
#include <cstdlib>
//some code...
i think you have issues in your make file,
tester: main.o simulator.o personqueue.o dogqueue.o character.o person.o dog.o
g++ -Wall main.cpp -lncurses -o tester
try something like this, though I have not tested the code,
tester: main.o simulator.o personqueue.o dogqueue.o character.o person.o dog.o
g++ -o tester main.o simulator.o personqueue.o dogqueue.o character.o person.o dog.o -lncurses