Memory Management in C

Memory management in C is essential for efficient and effective use of memory during program execution. C provides both static and dynamic memory allocation, and you must manage memory manually, especially for dynamic allocation.

1. Memory Segments in C:

Memory is divided into several regions:

• Text (Code) Segment: Stores the program's compiled code (instructions).
• Data Segment:
  • Initialized Data: Stores global and static variables initialized at compile-time.
  • Uninitialized Data (BSS): Stores global and static variables initialized to zero.
• Heap: For dynamic memory allocation at runtime (malloc, calloc, realloc, free).
• Stack: Stores local variables, function parameters, and return addresses. Grows and shrinks as functions are called and return.

2. Static vs Dynamic Memory:

• Static Memory Allocation: Memory for variables is allocated at compile-time and remains fixed throughout program execution (e.g., global variables).
• Dynamic Memory Allocation: Memory is allocated during runtime and can be resized or freed manually (heap memory).

3. Dynamic Memory Functions:

• malloc(): Allocates a specified number of bytes and returns a pointer to the first byte.

  void *malloc(size_t size);
  
  

  Example:

  int *arr = (int *) malloc(5 * sizeof(int));
  
  

  • Allocates memory for an array of 5 integers.
  • Memory is uninitialized.

• calloc(): Allocates memory for an array and initializes all bytes to zero.

  void *calloc(size_t nitems, size_t size);
  
  

  Example:

  int *arr = (int *) calloc(5, sizeof(int));
  
  

  • Allocates and initializes memory for an array of 5 integers.

• realloc(): Resizes an existing block of memory.

  void *realloc(void *ptr, size_t size);
  
  

  Example:

  arr = (int *) realloc(arr, 10 * sizeof(int));
  
  

  • Resizes the array to hold 10 integers.

• free(): Frees dynamically allocated memory to avoid memory leaks.

  void free(void *ptr);
  
  

  Example:

  free(arr);
  
  

4. Common Issues:

• Memory Leaks: Forgetting to free memory, which can exhaust memory.
• Dangling Pointers: Accessing memory after it has been freed.
• Double Free: Attempting to free the same block of memory more than once.