Compose the libFuzzer entry point

Challenge

Implement int call_under_test_with_buffer(const unsigned char *data, int size, int (*parser)(const char *)).

The function:

1. If size <= 0 or data == NULL or parser == NULL, return 0 (skip).
2. Allocate size + 1 bytes, copy data, NUL-terminate.
3. Call parser on the copy.
4. Free the copy.
5. Return 0.

This is the kernel of every libFuzzer harness for a string-parser.

Why this matters

The libFuzzer entry-point signature is muscle memory. Write it once; reuse forever.

Input format

data + size + parser callback.

Output format

0 always.

Constraints

No leaks. Always NUL-terminate.

Starter code

#include <stddef.h>
int call_under_test_with_buffer(const unsigned char *data, int size, int (*parser)(const char *)) { /* TODO */ (void)data; (void)size; (void)parser; return 0; }

Common mistakes

Forgetting +1 for NUL. Leaking on the early-return path.

Edge cases to handle

size == 0. NULL data. NULL parser.

Complexity

O(size).

Background lessons

• Fuzz harness design — defensively
• Memory safety — the whole bug class