Thread: Error only on Visual Studio

Hello fellows.
I have tested the above code to g++ and it's ok. It does compile.

Code:

class Player {
 private:
	 string name;
 public:
	 Player(const string &n)
	 {
		 name = n;
	 }

	 virtual ~Player() { }


	virtual const string & getType() const = 0;

	virtual Move play(const State &s) = 0;

	friend ostream & operator << (ostream &out, const Player &player);

};

ostream & operator << (ostream &out, const Player &player)
{
	out << player.getType() << " player " << player.name;

	return out;
}

I have tested on Visual Studio 2015 (C++14) and at the line out << player.getType() << " player " << player.name; i get the error error C2259: 'Player': cannot instantiate abstract class

I can't fix that error because i can't understand it. What's wrong ?

Yes, i do have code to test this function.
Yes, i do have main.
No i don't instantiate object of Player. Instead, i do instantiate subclasses of Player (such as GreedyPlayer) which are not abstract (all pure virtual functions have been overriden).

Just to add that in g++ it also runs fine. No errors, and the expected output comes "naturally".

Check attachements.

2 headers (one with the problematic code)
1 cpp with main.

This minimal edition compiles and run on g++ (linux).

I've tried on two different machines with VS 2015 Express edition (C++14).

Originally Posted by laserlight

I used to think that this was just being pedantic, until coming across a case where it really did matter: names that begin with an underscore followed by an uppercase character, or which contain consecutive underscores, are reserved to the implementation for any use. Hence, your header guard names _SP_PLAYER_ and _SP_MOVE_ are actually reserved and hence should not be used. Easy alternatives include SP_PLAYER_H_ and SP_MOVE_H_

Same thing here... I used to name things with an underscore until I've got a conflict... Same thing to the suffix _t for typedefs. Now, the tags of structures, unions and enums I use _s, _u and _e, respectively... And for typedefs I use _T (uppercase t). Specially glibc documentation tells us _t is reserved...

Thanks for the advices lasrlight.
This code is not for bussiness. I was just helping someone and, while i was so sure that it does compile, i was surprised.

The above is the minimal which is not been compiled either.

Code:

#include <iostream>
using namespace std;

class Player {
private:
	string name;
public:
	Player(const string &n)
	{
		name = n;
	}

	virtual ~Player() { }


	virtual const string & getType() const = 0;


	friend ostream & operator << (ostream &out, const Player &player);


};

ostream & operator << (ostream &out, const Player &player)
{
	out << player.getType() << " player " << player.name;

	return out;
}

/*+++++++++++++++++++++++++++++++++++++++++++++++++++*/
class GreedyPlayer : public Player
{
private:
	string type {"Greedy"};

public:
	GreedyPlayer(const string &n) : Player(n){}

	~GreedyPlayer() {}

	const string & getType() const	{ return type;}
};


int main() {

	Player *p = new GreedyPlayer("Tom");

	cout << *p;

	delete p;

 return 0;
}

I suppose that the problem hides somewhere behind friend and/or operator.

I have just found the solution.

The ostream couldn't find the way to print string. I've just included <string> and it does compile finally.

I've removed const from player and then the error changed to "no ostream const string operator exists" or something similar. So i've tried to include string and ta da.

But i have to admit that the compilation errors have lead me to another direction.

I used to think that this was just being pedantic, until coming across a case where it really did matter: names that begin with an underscore followed by an uppercase character, or which contain consecutive underscores, are reserved to the implementation for any use. Hence, your header guard names _SP_PLAYER_ and _SP_MOVE_ are actually reserved and hence should not be used. Easy alternatives include SP_PLAYER_H_ and SP_MOVE_H_

It may be my confusion for years. I believed the exact opposite. That is, i have to use underscore in front of, so as to avoid collision with reserved definitions. Thanks for the correct reminding.

"repetition is the mother of learning"