embedded-systems-overlay

name	embedded-systems-overlay
description	Domain overlay for embedded and firmware development. Extends language standards with memory-constrained, real-time, and hardware-interface rules.

Embedded Systems Overlay

Activates when sdlc-config.md sets domain.primary: embedded-systems or domain.secondary includes it.

Additional ERROR Rules

• No dynamic memory allocation (malloc/new) after initialization phase
• All ISR (Interrupt Service Routines) must complete within documented time budget
• No blocking calls in ISR context — use flags and deferred processing
• Peripheral registers accessed only through defined HAL (Hardware Abstraction Layer)
• All DMA buffers must be cache-aligned and use memory barriers
• Watchdog timer must be configured and fed — no infinite loops without WDT reset

Additional WARNING Rules

• Use volatile for all hardware-mapped registers and shared ISR variables
• Document worst-case execution time (WCET) for time-critical paths
• Stack usage must be analyzed and documented per task/thread
• Use fixed-point arithmetic over floating-point when FPU is unavailable
• Minimize global state — use module-scoped statics with accessor functions
• Power state transitions must be documented in state machine diagrams

Additional RECOMMENDATION Rules

• Use static memory pools over dynamic allocation
• Consider MISRA C (or C++) subset for safety-related code
• Use __attribute__((packed)) or #pragma pack only when protocol requires it
• Implement ring buffers for producer/consumer patterns
• Use compile-time assertions for struct size and alignment validation

Build & Debug

• Enable -Wstack-usage=N to catch deep stack usage
• Use objdump / size to verify memory footprint fits target
• Use logic analyzer / oscilloscope for timing verification
• Flash memory layout documented and verified against linker script