What is that

Question

https://code.sololearn.com/caf5RSPaN0hD/?ref=app
what is its name and how to use it efficiently

Answer 1

#include <iostream>
using namespace std;

int main() {
[[maybe_unused]]
int h;
return 0;
}

https://timsong-cpp.github.io/cppwp/n4659/dcl.attr.unused#1

for more:
https://en.cppreference.com/w/cpp/language/attributes

are you talking about this?

Answer 2

RKK yes it is something like that I saw it in a code

Answer 3

Thanks for all

Answer 4

https://www.google.com/amp/s/www.geeksforgeeks.org/attributes-in-c/amp/

https://en.cppreference.com/w/cpp/language/attributes