# C Code Review

Review {{input}} for correctness, safety, and best practices.

## Memory Safety
- Every `malloc`/`calloc`/`realloc` return value must be checked for NULL
- Every allocation must have a corresponding `free`; trace ownership through all code paths
- No buffer overflows: check array bounds before indexing; use `snprintf` not `sprintf`
- No use-after-free or double-free; set pointers to NULL after freeing
- No stack-allocated VLAs for untrusted sizes — use heap allocation with bounds checks

## Undefined Behaviour
- No signed integer overflow (use unsigned or check before arithmetic)
- No null pointer dereference — validate pointers before use
- No out-of-bounds reads/writes — validate indices against array size
- No uninitialized reads — initialise all variables at declaration
- Avoid relying on implementation-defined behaviour (e.g. right-shifting negative integers)

## String and I/O
- Use `strnlen`, `strncpy`, `strncat` — never the unbounded variants
- Validate `scanf`/`sscanf` field widths; check return values
- Sanitise all format strings passed to `printf`-family functions — never pass user data as format

## Error Handling
- Check the return value of every system call and library function
- Return meaningful error codes or set `errno`; do not silently ignore failures
- Clean up resources (files, sockets, memory) on every error path

## Code Quality
- Functions should do one thing; < 50 lines each
- Use `const` for pointer parameters that are not modified
- No global mutable state unless absolutely necessary; document it explicitly
- Compile with `-Wall -Wextra -Werror` and fix all warnings

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List findings as **Critical** (memory unsafety/UB/security) -> **Major** (bugs/resource leaks/unchecked errors) -> **Minor** (style/clarity). Cite each location and suggest the concrete fix.