Two stack variable address difference

Question

I have two int variables on stack as below code:

When i am substracting address of these two int variables , it should not be 4 or 8 instead of 1 ?
https://code.sololearn.com/cWlocLTzz03J/?ref=app

Answer 1

Ketan Lalcheta Here's a few things to consider:
Your second code:
int x;
float y;
float z;
cout << &x - &z ;
will not compile. So it won't print anything (as you say 2).
▪︎A subtraction is allowed on pointers of the same type, this will result the difference in units of that data type size. As you get 1 on the attached code.
▪︎to get the difference of memory addresses you can cast pointers to a same size data type
cout << (long)&x - (long)&y
if long int and pointer be the same size (8 bytes on a 64bit machine). or multiply result by sizeof(type)
▪︎ subtraction of two same type pointers are allowed, addition or any other operation aren't.
▪︎it's not good nor common practice to do what you did, even proper use needs much attention to avoid bugs.
▪︎add, sub by a const is fine, note that (int *)+n jumps n*sizeof(int) bytes in memory not n bytes.
▪︎a section disassembly of your code attached, note lines 20, 25 and 26.

https://code.sololearn.com/cckplrEP9HOf/?ref=app

Answer 2

when you subtract pointers, their difference represents the number of data items between the pointers. in case of int ( assuming sizeof int is four bytes on your system ), the difference between pointers that are four-bytes apart is
( 4 / sizeof( int ) ), which works out to 1.

https://www.sololearn.com/compiler-playground/cu25VVyqRZI7

Answer 3

You are getting such answer because pointer arithmetic works in multiple of size of the data type the pointer is pointing to instead of raw bytes between two memory locations.

Answer 4

Thanks MO ELomari , Mirielle and Arsenic

Got idea and basically pointer arithmatic is used to point elements inside array ..like arr is base address of int arr[10] and arr+1 would point to next element. Is pointer arithmatic used elsewhere ?

I believe below is not a good choice but it does print output as 2.
int x = 4;
FLOAT y = 5;
Float z = 6;

cout << &x - &z << endl;