5W1H Specification

• Who: Maintainers
• What: Verify and enhance compiler deprecation warnings
• Where: All header files with deprecated APIs
• When: v2.x series (Phase 2)
• Why: Help users identify deprecated API usage at compile time
• How: Review and update [[deprecated]] attributes with clear migration messages

Parent Issue

Part of #213 - Deprecated API Removal Plan for v3.0.0

Scope

• Verify all deprecated APIs have [[deprecated]] attribute
• Ensure deprecation messages include migration hints
• Consider enabling -Wdeprecated in CI for dependent projects

Acceptance Criteria

• All deprecated APIs have [[deprecated("migration hint")]] attribute
• Compiler warnings clearly indicate replacement APIs