Generic in-place memory swap

Challenge

In dynamically typed languages, swapping variables is trivial. In C, generic swapping across arbitrary data types requires swapping raw memory byte-by-byte through unsigned char* pointers.

Your Task

Implement:

void generic_swap(void *a, void *b, size_t size);

Swap size bytes between memory addresses a and b.

Rules

1. If a == NULL, b == NULL, a == b, or size == 0, do nothing.
2. Cast pointers to unsigned char* and swap all size bytes in place.

Example

int x = 10, y = 20;
generic_swap(&x, &y, sizeof(int)); // x is now 20, y is now 10

double d1 = 3.14, d2 = 2.71;
generic_swap(&d1, &d2, sizeof(double)); // d1 is now 2.71, d2 is now 3.14

Input format

a, b: generic memory pointers; size: byte length to swap.

Output format

Modifies memory at a and b in place.

Constraints

C11 freestanding. Swap byte-by-byte.

Starter code

#include <stddef.h>

/* Swap size bytes between memory locations a and b. */
void generic_swap(void *a, void *b, size_t size) {
    (void)a; (void)b; (void)size;
}

Common mistakes

Allocating dynamic memory for temporary buffer; sign-extending signed char during swap.

Edge cases to handle

a == b does nothing; size == 0 does nothing; NULL pointers do nothing.

Background lessons

• Pointer basics