Question

How could you confirm that "the stack" that local variables are stores on grows downwards? (C++)

Answer 1

Stack can grow downward/upward depending on environment for which code is compiled.
Generally stack grows down from high memory, and the heap grows upwards from low memory, so they will never collide each other but there are some cases in which stack goes upwards.

To check whether the stack grow upwards or downwards we can write a program and understanding a certain condition which will help us to find whether our stack goes upwards or our stack goes downward.

If there's a variable which is created in a function compared to a variable which is coming from the main has lesser address it means stack grows downwards.

In short if main function address us greater than local function it means that stack grows downwards.

The stack grow downward so that program can be compiled in a low memory address, and the stack with the remaining memory. Stack initialization could be performed before program load, simplifying programs.

CODE:

#include <iostream>
#include <string>
using namespace std;
void check(int *mainVar)
{
int temp;
if (mainVar < &temp) // & is used for address
cout<<"Stack grows upwards"<<endl;
else
cout<<"Stack grows downwards"<<endl;
}
  
int main()
{
// fun's local variable
int mainVar;
  
check(&mainVar); // mainVar address is passed to the function
return 0;
}

OUTPUT:

CODE:

WHEN EVER A VARIABLE IS CREATED IN A FUNCTION IT WILL ALWAYS HAVE A LESSER THAN MAIN FUNCTION ADDRESS CONFIRMING THAT IT STACK FOR LOCAL VARIABLES IN C++ GOES DOWNWARDS

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