06. Stack Memory

Stack

In C++ stack memory is a place where local variables are stored upon declaration. The stack is also used for storage of parameters passed to function. The stack is a LIFO( Last In First Out) data structure that is organized and controlled by the CPU. Every time that an action inside of a function triggers the declaration of a new variable, it is pushed onto the stack by that parent function. After that when function exits, and resolves its work, all of the data from variables, which are pushed into the stack are freed and that part of memory becomes available for other data. The advantage of using the stack region of memory for variable storage is that memory is managed by the CPU, freeing you from any concerns. Another advantage of this approach is that the CPU is in charge and in control during this process. With that in mind, you get an optimized and efficient process.

int stackFunction(int x){
    // integer y is stored into stack
    int y = 5;
    x+=y;
    // in the moment when this function exits, or returns a value, 
    // stack removes space occupied by y and shrinks the stack itself
    return x;
}

Generally speaking stack is a limited resource and it shouldn't be used for anything large in memory size. Problems like out of memory stack is stack buffer overflow. It's a serious problem to solve and it can be encountered in small, primitive systems, such as microcontrollers found in embedded systems.