no matching function for call to explicit copy-constructor

[Dario]

Trying to compile the following code-fragment with g++ 2.96:

class Entity {
private:
void * data;
public:
explicit Entity(int);
explicit Entity(Entity &);
virtual ~Entity();
void makeSomething();
};
Entity f(int n) {
Entity result(n);
result.makeSomething();
return result;
}

I obtain the error:
no matching function for call to `Entity::Entity (Entity &)'
on the the row:
return result;

It's a my fault?

The only way to get away from the error is to change the copy
constructor into:

/* explicit */ Entity(Entity &);

But I want to use explicit...

Is there any other option to solve my problem?

- Dario

[Attila Feher]

Dario wrote:

Trying to compile the following code-fragment with g++ 2.96:

class Entity {
private:
void * data;
public:
explicit Entity(int);
explicit Entity(Entity &); explicit Entity(Entity const &); virtual ~Entity();
void makeSomething();
};
Entity f(int n) {
Entity result(n);
result.makeSomething();
return result;
}

I obtain the error:
no matching function for call to `Entity::Entity (Entity &)'
on the the row:
return result;

It's a my fault?
Yes. You made the copy constructor explicit.
The only way to get away from the error is to change the copy
constructor into:

/* explicit */ Entity(Entity &);

But I want to use explicit...

Is there any other option to solve my problem?

Not really. Making the copy constructor explicit does not seem to be a good
idea.

Of course - in any other case - you could write Entity(result), but not in a
return statement. That would count as copy initialization of the return
value and an accessible (implicit) copy constructor has to be present.

I think you have no choice but to remove the explicit.

--
Attila aka WW

[tom_usenet]

On Mon, 22 Sep 2003 12:28:57 +0200, Dario <da***@despammed.com> wrote:

Trying to compile the following code-fragment with g++ 2.96:

class Entity {
private:
void * data;
public:
explicit Entity(int);
explicit Entity(Entity &);
Are you sure you don't want:
Entity(Entity const&);
? If not, why not?
virtual ~Entity();
void makeSomething();
};
Entity f(int n) {
Entity result(n);
result.makeSomething();
return result;
}

I obtain the error:
no matching function for call to `Entity::Entity (Entity &)'
on the the row:
return result;

It's a my fault?
Yes, since you made the copy constructor "explicit".

The only way to get away from the error is to change the copy
constructor into:

/* explicit */ Entity(Entity &);

But I want to use explicit...

Why? Making a copy constructor explicit is done precisely to prevent
that type from being returned by value or used as a pass-by-value
parameter to a function, while still allowing local copies to be made.
What you you using explicit for?

Tom