Memory Management: The Heap and The Stack

In professional C development, memory leaks are non-negotiable. Understanding malloc, calloc, realloc, and free is just the start.

Stack vs Heap: Performance Implications

• Stack: Fast, scoped, automatic management. Limited size (typically 1-8 MB).
• Heap: Slower, manual management, flexible size. Can lead to fragmentation.

The malloc Internals

When you call malloc, the C library (brk/sbrk or mmap on Linux) asks the OS for a block of memory. It keeps track of "free lists" to manage these blocks.

c code
#include <stdlib.h>

void industry_pattern() {
    size_t n = 1000;
    // calloc initializes to zero - safer for sensitive data
    int *data = (int *)calloc(n, sizeof(int));
    
    if (data == NULL) {
        perror("Failed to allocate memory");
        return;
    }

    // Work with data...

    free(data);
    data = NULL; // Defensive programming
}

Detecting Leaks with Valgrind

No senior C developer ships code without running a memory profiler.

bash code
valgrind --leak-check=full ./my_program

Common Pitfalls

1. Memory Leak: Forgetting to free.
2. Double Free: Calling free on the same address twice (crash/vulnerability).
3. Heap Overflow: Writing past the allocated buffer.
4. Buffer Overrun: The source of thousands of CVEs. Use strncpy instead of strcpy.