Why does C++ allow a function and a class have a same name?

#include 

using namespace std;

struct A
{
    A()
    {
        cout << "A::A()" << endl;
    }
};

int A()
{
    cout << "void A()" << endl;
    return 0;
}

int main()
{
    auto v = A();
}

The output is:

void A()

Why does C++ allow a function and a class have a same name?

Solved

I believe this comes down to backwards compatibility with C.

In C, when you declare a struct like you did, you then have to refer to it as struct A, not just A. For example:

void A() {}

struct A {};

void f()
{
    A();

    struct A x; // works fine
    A y; // does not compile
}

In this context, it makes sense to allow A to mean two different things, because it's always clear which one you mean, depending on whether you used struct or not.

In C++, structs (and classes) can be referenced directly, without the need to use the struct keyword. This introduces the ambiguity you're concerned about, but the alternative is that valid C code like the one above would not be valid C++ code, which is even worse.

Why? Because that's the way the language is! The A::A() function belongs in a different "domain" than A().

It's similar to namespaces, where the same name can exist in multiple domains.

It's also somewhat similar to having a thousand different functions (or scopes) all having their own loop counter called i.