1. Dynamic Memory Copy Challenge
CSCE 121
J. Michael Moore

2. Assignment
Output:
(7, 3) 11
int a = 7; int b = 3; cout << "(" << a << ", " << b <<")"<<endl; int c; c = b; c = 11; cout << c << endl;

3. Assignment Expectation is that information is copied.
Expectation is that changes to the copy do not affect the source.

4. Assignment Output: (7, 3) (7, 11) 11
int* d = new int(7); int* e = new int(3); cout << "(" << *d << ", " << *e <<")"<<endl; int* f; f = e; *f = 11; cout << *f << endl;

5. Copy happens with pointers!
Pointer address is copied
Unfortunately, both now point to the same memory address.

6. Shallow vs. Deep Copy Shallow Copy Deep Copy b ← a
b is assigned with a
Shallow Copy
Deep Copy a 7 a 7 b b 7

7. Shallow Copy output identifier stack heap
class TwoNums { int* num1; int* num2; public: TwoNums(int x, int y): num1(new int(x)), num2(new int(y)) {} // stuff }; int main() { TwoNums a(4, 7); TwoNums b = a; }
num1 b 7
num2
num1 a
num2 4
identifier
stack
heap

8. Deep Copy output identifier stack heap 7
class TwoNums { int* num1; int* num2; public: TwoNums(int x, int y): num1(new int(x)), num2(new int(y)) {} // stuff }; int main() { TwoNums a(4, 7); TwoNums b = a; } 4
num1 b 7
num2
num1 a
num2 4
identifier
stack
heap

9. Assigning Class Objects
By default each data member is copied.
Pointer addresses are copied, i.e. shallow copy.
After copy, each identifier
has the same value(s)
uses the same memory address
Expectation is a deep copy.
uses a different memory address
We can ensure deep copy happens. We’ll see how soon!