How does std::map construct complex objects?

[AlwaysLearning]

How does std::map construct complex objects if no constructor is written for it?

class Complex{
	float a,b,c;
};

void main(){
	map<int,Complex>  Test;

	Complex &Item = Test[0];
}

Item's members are all zeroed out.

[Zhuge]

If you don't explicitly declare a constructor, the compiler generates a default one and map uses that one.

[AlwaysLearning]

True, but the default constructor doesn't zero out the members. Just as declaring an int without initializing it will provide a random value.

Unless there is a default constructor that does this, is there?

[firedraco]

It will. If you do something like:

int a;, then a is not initialized.

However, inside a template class, ints are intialized to 0 if you construct them, so you can do stuff like this:

template <class T>
T some_func() {
    T _type = T();
    //...
}