Undefined reference but it is defined.

[Croolsby]

I made this snippet to test whether or not the pointer would be destroyed when the A::add method goes out of scope. But when I tried to compile I got these errors:

obj\Debug\main.o||In function `main':|
|7|undefined reference to `A::A()'|
|10|undefined reference to `A::add(B*)'|
|11|undefined reference to `A::soundOff()'|
||=== Build finished: 3 errors, 0 warnings ===|

Here is my code:

main.cpp

#include <iostream>
#include "A.h"
#include "B.h"

int main()
{
	A obj;
	B b(1);
	B* bpnt = &b;
	obj.add(bpnt);
	obj.soundOff();

	std::cin.get();
}

A.h

#ifndef A_H
#define A_H
#include "B.h"
#include <vector>
#include <iostream>

class A
{
public:
	A();
	void add(B*);
	void soundOff();
private:
	std::vector<B*> bVect;
};
#endif 

A.cpp

#include "A.h"

A::A()
{
	std::cout << "A created.";
}

void A::add(B* b)
{
	bVect.push_back(b);
}

void A::soundOff()
{
	for (unsigned int i = 0; i < bVect.size(); i++)
	{
		bVect[i]->talk();
	}
}

B.h

#ifndef B_H
#define B_H
#include <iostream>

class B
{
public:
	B(int);
	void talk();
private:
	int id;
};
#endif 

B.cpp

#include "B.h"

B::B(int i)
{
	id = i;
}

void B::talk()
{
	std::cout << "ID: " << id;
}

It looks to me that I have A.h included in main.cpp and the constructor and methods are defined in A.h. So what is causing this?

[Peter87]

Did you compile and link all the .cpp files?

[Croolsby]

I'm new to this. I don't know what you mean by your question. I'm using code::blocks with the GNU GCC Compiler. I'm not sure if that answers your question.

I thought code::blocks does all the compiling and linking for me when I tell it to build.
Also, all the header and cpp files are selected as build targets.

[Peter87]

I thought so too. Are all the files in the same project?

[Croolsby]

Yes they are, but just to make sure, I'm going to delete this project and make a new one.

EDIT:

Strange, I made a new empty project and copy and pasted the code into new files. It worked this time.

I suspect this might have been caused somehow due to the fact that the original project was actually an old project that I gutted (deleted all the header and cpp files) and I added this code in without make a brand new project.

Thanks for the idea to make a new project.

Unrelated to the original problem, do you know if this code snippet would keep a pointer in the vector even after the add method goes out of scope?

I ran it and it seems that it does keep the pointer. I'm wondering why. The pointer I passed into the add method die when it goes out of scope, so I am guessing that when that pointer got passed into the push_back method, a clone of the pointer was made? When does the pointer inside the vector die?

[Peter87]

Yes the vector will store a copy of the pointer. The pointer will "die" when you delete it or the vector is destructed.