zireael-header-layering

name	zireael-header-layering
description	Prevent include cycles and platform-boundary leaks by enforcing header layering.
metadata	{"short-description":"Headers + include discipline"}

When to use

Use this skill when:

• adding new headers or refactoring includes
• encountering circular dependencies
• tightening the platform boundary

Source of truth

• docs/REPO_LAYOUT.md — dependency direction and #ifdef policy
• docs/LIBC_POLICY.md — stdlib usage constraints

Include layering rules (must follow)

src/util/      → OS-header-free, no internal deps
      ↑
src/unicode/   → may include util; OS-header-free
      ↑
src/core/      → may include util, unicode, platform interface; OS-header-free
      ↑
src/platform/  → implements zr_platform.h; may include OS headers

Specific rules

• src/util/** MUST be OS-header-free
• src/unicode/** may include src/util/** only; MUST be OS-header-free
• src/core/** may include util, unicode, and zr_platform.h; MUST be OS-header-free
• src/platform/** implements zr_platform.h; may include OS headers

Best practices

• Prefer forward declarations in headers to avoid deep include trees
• Keep ABI-visible headers POD-only (fixed-width ints)
• Ensure no OS headers are transitively included by core/unicode/util
• Platform #ifdef exists only in platform backends and selection TU

Checklist

• No OS headers in core/unicode/util
• No circular includes
• Forward declarations where possible
• ABI headers use fixed-width types only