I know how to use auto keyword in for loop to iterate this array either by value or reference.
struct A { void fun() {}; }; int main() { A a[2]; // Value for (auto x : a) { x.fun(); } // Ref for (auto& x : a) { x.fun(); } // Pointer //for (...) { x->fun(); } } So I am looking third version of this convention. How do I use pointer here?
A a[2]; for(auto& x_:a){ auto* x = &x_; // code } 
You don't. If you want a pointer, either write a classical for-loop, or loop by reference and take the address.
I'm not recommending it, but if you insist on using pointer -> syntax, just make an array of A* and treat it like a value (i.e. do regular auto in the range-for loop)
#include <iostream> struct A { void fun() { std::cout << "fun \n"; }; }; int main() { A* a[2]; // Pointer for (auto x : a) { x->fun(); } } 
-> syntax. Updated the answer, tnx.