Discussion: Hack the Planet!
Execute the code to understand the output and gain insights into the workings of the system stack during function calls.
We'll cover the following...
Run the code
Now, it’s time to execute the code and observe the output.
#include <iostream>int getUserId() { return 1337; }void restrictedTask1(){int id = getUserId();if (id == 1337) { std::cout << "did task 1\n"; }}void restrictedTask2(){int id;if (id == 1337) { std::cout << "did task 2\n"; }}int main(){restrictedTask1();restrictedTask2();}
Understanding the output
The id variable in the restrictedTask2()function has not been initialized and has an indeterminate value. To use its value is an undefined behavior. Anything can happen when a program runs into undefined behavior; the C++ standard makes no guarantees. Even the part of the program that happened before we took the value of id is undefined!
However, if we run this program, it will probably print both did task 1 and did task 2, at least if we compile without optimizations. So the value 1337 magically teleported from restrictedTask1() to restrictedTask2()! How could this happen?
Function call stack
Most systems use a stack for local variables. The restrictedTask1() ...