Resource Management

Use RAII for all resource acquisition and release (raii)

Resources — IRQ enable/disable state, port numbers, file handles, DMA buffers, lock guards — must use the Drop trait for automatic cleanup. Manual enable()/disable() call pairs are rejected.

// Good — RAII guard ensures IRQs are re-enabled
fn disable_local() -> DisabledLocalIrqGuard { ... }

impl Drop for DisabledLocalIrqGuard {
    fn drop(&mut self) {
        enable_local_irqs();
    }
}

// Bad — caller can forget to re-enable
fn disable_local_irqs() { ... }
fn enable_local_irqs() { ... }

Prefer lexical lifetimes so the Rust compiler inserts drop automatically, rather than calling drop() manually. When the default drop order is incorrect, use explicit drop() calls.

See also: PR #164.