Question

We discussed in the class that there are 3 major issues with pointers and dynamic memory allocations .

• Memory fault: Invalid memory access  
• Memory leak
• Memory corruption

Identify the line numbers in the code snippet below for each issue listed above with one line explaining your reason.

A sample answer:

- Memory fault: line number 6: because a for-loop can't iterate more than 1,000,000

- Memory leak: line number 9; because ....

- Memory corruption: line number 7; because ....

[code snippet]

1. int *intPtr = new int;
2. int *intPtr2 = intPtr;
3. int *intPtr3 = x00FF1234;  //Assume this is a valid address
3. *intPtr  = 2123;
4. *intPtr2 = *intPtr = 11;
4. delete(intPtr)
5. (*intPtr2)++;

6. for (int i = 0; i <= 1000000; i++) {
7.     int * intPtr = new int[1000];
8.     for (int j = 0; i <= 1000; j++) 
9.          intPtr[j] = *intPtr3++;
10. }

Answer 1

Memory leak is caused by programmers when they create a memory in heap and does not delete it.

The line 8 with for loop has an error as the checking condition is with respect to 'i' and not 'j'.

In line 9 memory is allocated for intPtr[j] but is not deleted afterwards which leads to memory leak. So add these 3 lines of code after the 9th line to overcome memory leak :

for (int j = 0; j<= 1000; j++)

         delete Ptr[j];

delete Ptr;

The alteration of computer system memory without explicit assignment is known as memory corruption.

In line 7 an array is used in a loop, with wrong or incorrect terminating condition, so there is a chance of manipulating the memory beyond array bounds accidentally. When we use memory beyond memory that was allocated, it leads to memory corruption.