lab-rv32i-freertos-queue/doc/card-plan.md

K10 — Queue and StaticQueue<T, N>

Position

• Series: FreeRTOS C++
• Lesson: L09, card K10
• Duration: 30 minutes
• Platform: Hazard3 / RV32I, FreeRTOS V11.3.0
• Message: 12-byte trivial Sample, capacity 2

Outcome

The student explains byte-copy semantics, designs a trivial message, proves a copy survives source mutation, compares dynamic and caller-owned static queue storage, and handles full/empty states with explicit bounded timeouts.

Lesson plan

Time	Mode	Evidence
0–5	type contract	Sample passes; owning VectorV1 fails
5–10	create	dynamic cost 128 B; static delta 0 B
10–15	copy	send, mutate source, receive unchanged copy
15–20	storage	inspect first 12 static storage bytes
20–25	full/timeout	capacity 2; third send fails after 2 ticks
25–30	FIFO/drain	values 0x2222 then 0x3333; empty receive fails

Acceptance

• sizeof(Sample)==12 reaches both create APIs;
• dynamic cost is positive and recovered by RAII destruction;
• static create has zero heap delta and its buffers are in .bss;
• received value remains 0x1111 after source becomes 0xDEAD;
• storage snapshot equals the first sent Sample byte-for-byte;
• full count is 2, third send returns false after at least 2 ticks;
• FIFO and non-blocking empty receive are correct;
• non-trivial owning message fails for the pinned static-assert reason;
• target exits with PASS.

Main traps

1. Queue storage is a byte copy, not a C++ object owner.
2. sizeof(pointer) plus an object address is a different and invalid contract.
3. A trivially-copyable pointer still needs an external lifetime policy.
4. portMAX_DELAY must not be hidden as a convenient default.
5. Static queue control and byte storage must both outlive the queue.