Memory leak concept in C++ - Step-by-Step Execution

Concept Flow - Memory leak concept

Allocate memory with new

↓

Use the allocated memory

↓

Forget to delete memory

↓

Memory still reserved

↓

Program continues, memory not freed

↓

Memory leak occurs

This flow shows how memory is allocated but not freed, causing a memory leak.

Execution Sample

C++

int* ptr = new int(10);
// use ptr
// forgot to delete ptr
// memory leak occurs

This code allocates memory for an int but never frees it, causing a memory leak.

Execution Table

Step	Action	Memory Allocated	Pointer Value	Memory Freed	Leak Status
1	Allocate memory with new int(10)	1 int block	Address 0x1000	No	No
2	Use the allocated memory	1 int block	Address 0x1000	No	No
3	Forget to delete pointer	1 int block	Address 0x1000	No	Yes
4	Program continues	1 int block	Address 0x1000	No	Yes

💡 Memory was never freed, so leak remains until program ends.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
ptr	nullptr	0x1000	0x1000	0x1000	0x1000

Key Moments - 2 Insights

Why does the memory leak happen even though we have a pointer?

Because the pointer 'ptr' still points to the allocated memory but we never call 'delete ptr' to free it, as shown in execution_table step 3.

Does the memory get freed automatically when the pointer goes out of scope?

No, in C++ you must manually free memory with 'delete'. The pointer going out of scope does not free the memory, causing a leak (see execution_table step 4).

Visual Quiz - 3 Questions

Look at the execution table, what is the pointer value after step 2?

A nullptr

B Address 0x2000

C Address 0x1000

D Deleted

💡 Hint

Check the 'Pointer Value' column at step 2 in the execution_table.

At which step does the memory leak start to exist?

A Step 2

B Step 3

C Step 1

D Step 4

💡 Hint

Look at the 'Leak Status' column in the execution_table.

If we add 'delete ptr;' after step 2, how would the 'Memory Freed' column change at step 3?

A Changes to Yes

B No change, still No

C Pointer value becomes nullptr

D Leak status becomes Yes

💡 Hint

Deleting pointer frees memory, so 'Memory Freed' becomes Yes at step 3.

Concept Snapshot

Memory leak in C++ happens when you allocate memory with 'new' but forget to free it with 'delete'.
Pointer still holds address but memory stays reserved.
Program loses track of memory, causing leak.
Always pair 'new' with 'delete' to avoid leaks.
Memory leaks waste resources and can crash programs.

Full Transcript

This visual execution shows how memory leaks happen in C++. First, memory is allocated using 'new', and a pointer stores its address. The program uses this memory. However, if the programmer forgets to call 'delete' on the pointer, the memory remains allocated even after the pointer is no longer used. This causes a memory leak because the program cannot reuse or free that memory. The pointer variable itself does not free memory automatically when it goes out of scope. To prevent leaks, every 'new' must be matched with a 'delete'.