Memory Leaks & Common Pitfalls

A memory leak happens when allocated memory is never freed — the program loses every reference to it, so it can never be reclaimed until the process itself exits.

void leaky(void) {
    int *p = malloc(100 * sizeof(int));
    // ... no free(p) before p goes out of scope — leaked!
}

A short-lived program leaking a little memory may never visibly matter; a long-running server doing this repeatedly will eventually exhaust available memory. The rule of thumb: every successful malloc/calloc/realloc needs exactly one matching free, on every code path, including early returns and error handling.

Common mistakes

• Returning early from a function after an error, skipping a free() call further down that was meant to run in every case.