Memory Safety c Skill.instructions

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---
description: 'Memory safety analysis for C code — allocation pairing, pointer lifecycle, buffer bounds, and undefined behavior checks'
applyTo: '**/*.c, **/*.h'
---
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When reviewing or analyzing C code, apply the following checks in order.

For every claim, finding, or recommendation, you MUST distinguish:
- **KNOWN**: directly observed in code, logs, or documentation
- **INFERRED**: logically derived from KNOWN facts
- **ASSUMED**: stated for clarity but not yet confirmed

Do not present INFERRED or ASSUMED conclusions as KNOWN facts. When uncertain,
say so explicitly rather than guessing.

## Phase 1 — Allocation and Deallocation Pairing

- Identify every allocation site (malloc, calloc, realloc, custom allocators).
- Trace each allocation to its deallocation site.
- Flag any path where deallocation is missing, occurs multiple times, or
  occurs in a different lifetime scope than the allocation.

## Phase 2 — Pointer Lifecycle

- Identify every pointer that is passed across a function boundary, stored in
  a struct, or returned from a function.
- Verify the pointed-to object outlives all pointer uses.
- Flag any pointer that may be used after its referent is freed or goes
  out of scope.

## Phase 3 — Buffer Boundaries

- Identify every read or write through a pointer with an associated length.
- Verify the length is validated before use.
- Flag any access that may exceed the allocated size.

## Phase 4 — Undefined Behavior

- Flag signed integer overflow, invalid pointer arithmetic, uninitialized
  reads, and type-punning that violates strict aliasing.
- Label each finding with KNOWN, INFERRED, or ASSUMED per the epistemic
  labeling rules above.

## Project Context

**Focus**: Stack lifetime hazards at driver/kernel boundaries.
Every finding must cite an exact code excerpt with file path and line
numbers. Do not report findings you cannot cite directly.