constructor and destructor not called

[vuurrobin]

hello everybody

I have a piece of code where I create an object with the default constructor, but the constructor (and destructor) isn't called. I use
ConstructorTest a();
to create the object, which should just call the default constructor. If I remove the (), it does work.

how come the constructor isn't called when using ()?

here is the entire code:

#include <iostream>
using namespace std;


class ConstructorTest
{
    private:
        const char *name;

    public:
        //default constructor
        ConstructorTest() : name("no name")
        {
            cout << "calling ConstructorTest default constructor from: " << name << endl;
        }

        //custom constructor
        ConstructorTest(const char *name) : name(name)
        {
            cout << "calling ConstructorTest custom constructor from: " << name << endl;
        }

        //copy constructor
        ConstructorTest(const ConstructorTest& a) : name(a.name)
        {
            cout << "calling ConstructorTest copy constructor from: " << name << endl;
        }


        //destructor
        ~ConstructorTest()
        {
            cout << "calling ConstructorTest destructor from: " << name << endl;
        }
};


void func()
{
    cout << "entered func" << endl;
    ConstructorTest a();
    cout << "leaving func" << endl;
}


int main()
{
    cout << "Hello world!" << endl;

    func();

    cout << "Goodbye world!" << endl;
    return 0;
}

and here is the output:

Hello world!
entered func
leaving func
Goodbye world!

Process returned 0 (0x0) execution time : 0.087 s
Press any key to continue.

[Disch]

line 41 does not create an object of ConstructorTest, it declares a function which returns a ConstructorTest and takes no parameters.

A solution to this is to leave off the parenthesis.

void func()
{
    cout << "entered func" << endl;
    ConstructorTest a;   //  <--- no parenthesis
    cout << "leaving func" << endl;
}

EDIT: but now that I actually read what you typed, you already knew that! XD

Sorry. But yeah -- the compiler thinks you're making a function, not an object.

[vuurrobin]

now why would the compiler think I would declare a function inside another function. silly compilers.

anyway, is there any situation where using () wouldn't result in a function declaration?

[sdbala]

when a constructor doesn't have a parameter then u just call it using a variable name
BUT if they do then i think u need to call it your way using the brackets with the parameter values

[Disch]

now why would the compiler think I would declare a function inside another function. silly compilers.

I agree it's absurd. But it's not the compiler's fault -- it's the language.

anyway, is there any situation where using () wouldn't result in a function declaration?

Yes.

// assume foo is a class name

foo* bar = new foo();
somefunction( foo() );

foo barb = foo();
barb = foo();

//and I'm sure there are others 

Basically it will only get confused as a function if you make foo appear as if it's the return type.

Here's a related read:

http://www.parashift.com/c++-faq-lite/ctors.html#faq-10.19