Why can MyClass foo() access private default constructor?

July 18, 2022

The following code:

#include <iostream>

using namespace std;

class Myclass
{
private:
    Myclass ();

public:
    int num;
};

int main()
{
    Myclass foo();

    return 0;
}

Compiles without any warnings or errors in Eclipse.

However

#include <iostream>

using namespace std;

class Myclass
{
private:
    Myclass ();

public:
    int num;
};

int main()
{
    Myclass foo;

    return 0;
}

Gives me this error: error: 'Myclass::Myclass()' is private within this context

Why does foo give me this error while foo() doesn’t?
Is foo() being mistaken as a function or does date_type name() have a special meaning?

>Solution :

Why can MyClass foo() access private default constructor?

It cannot (fancy hacks that allow you to call a private constructor aside).

Is foo() being mistaken as a function

Myclass foo(); is a function declaration. The mistake is to expect it to be something else. To call the constructor write:

Myclass foo;  // or
Myclass foo{};

As this mistake is rather common, compilers typically warn about it. Don’t ignore warnings, and crank up the warning level when there was no message for your code.