Confusion about inline function

Question

I have a question regarding inline function.

#include <iostream>
using namespace std;

class A 
{
public:
    inline void fun()
    {
        int i=5;
        cout<<i<<endl;
    }
};

int main() 
{
    A a1;
    int i = 2;
    a1.fun();
    cout<<i<<endl;
    return 0;
}

In above program, when function fun() was called, the compiler should have made copy of this function and insert into main function body because it is inline.

So, I have a question, Why doesn't compiler give an error of variable int i; being re-declared?

Answer 1

You seem confused about scopes. They're not "within the same" scope

You can declare multiple variables with the same name at different scopes. A very simple example would be the following:

int main()
{
    int a;       // 'a' refers to the int until it is shadowed or its block ends
    { 
        float a; // 'a' refers to the float until the end of this block
    }            // 'a' now refers to the int again
}

Inline expansion is not pure text replacement (as opposed to macros).

Whether a function is inlined or not has no effect on semantics Otherwise the program would behave differently depending on whether the function was inlined or not, and return statements would not behave properly at all.