C ++哪个构造函数将被调用

Question

If suppose in a class I have two constructors

Room()
{
length = 0;
width = 0;
}

&

Room(int value = 8)
{
length = width = 8;
}

Now if from main I call using:

Room obj1;
obj.display();

which constructor will be called or will it throw error? I think that it will throw error as compiler will not be able to call the correct constructor because of two same type of constructors present.Is it correct ?

Answer 1

call of overloaded 'Room()' is ambiguous

so it won't be compile

and you can use codepad as an online compiler

Answer 2

A default constructor is a constructor that either has no parameters, or if it has parameters, all the parameters have default values.

In this case code will not compile... You can read more about default constructor from here

Answer 3

Assuming that this will be the complete program

#include <iostream>
struct Room
{
    int length;
    int width;
    Room()
    {
        length = 0;
        width = 0;
    }
    Room(int value = 8)
    {
        (void)value;
        length = 8;
        width = 8;
    }
};
int main()
{
    Room obj1; // ambiguous call
    std::cout << obj1.length << "\n";
    return (0);
}

This code will not compile because of an ambiguous call to the constructor of Room for the declaration of obj1 .