Handout 33

Fun With Structs

The question of interest is, "when we have an array as part of a struct, and that struct is passed by value to a function, is a copy of the array stored on the run-time stack?" In the following example the addresses of the struct and another variable are displayed. Clearly the copy of the array is stored on the run-time stack.

#include <iostream.h>

struct myStruct {
	int x;
	float y[100];
};

void tester(int, struct myStruct);

int main() {

	struct myStruct theStruct;
	cout << "in main address =              " << &theStruct << endl;
	cout << "in main struct int address =   " << &theStruct.x << endl;
	cout << "in main struct array address = " << &theStruct.y << endl;
	
	tester(1, theStruct);
	
	return 0;
}

void tester(int i, struct myStruct a) {
	cout << "in tester struct address =       " << &a << endl;
	cout << "in tester int i address =        " << &i << endl;
	cout << "in tester struct int address =   " << &a.x << endl;
	cout << "in tester struct array address = " << &a.y << endl;
}

/* program output

in main address =                0x0012FDEC
in main struct int address =     0x0012FDEC
in main struct array address =   0x0012FDF0
in tester struct address =       0x0012FC0C
in tester int i address =        0x0012FC08
in tester struct int address =   0x0012FC0C
in tester struct array address = 0x0012FC10

*/