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Seal the DAC trait to prevent UB #94

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Seal the DAC trait to prevent UB #94

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22 changes: 13 additions & 9 deletions src/dac.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -87,25 +87,29 @@ pub trait DacPin {
fn enable(&mut self);
}

pub trait Pins<DAC> {
type Output;
mod sealed {
// This trait is unsafe and sealed because we use MaybeUninit to
// return an instance of the type, and should only be used on ZSTs.
pub unsafe trait Pins<DAC> {
type Output;
}
}

impl Pins<DAC> for PA4<Analog> {
unsafe impl sealed::Pins<DAC> for PA4<Analog> {
type Output = C1;
}

impl Pins<DAC> for PA5<Analog> {
unsafe impl sealed::Pins<DAC> for PA5<Analog> {
type Output = C2;
}

impl Pins<DAC> for (PA4<Analog>, PA5<Analog>) {
unsafe impl sealed::Pins<DAC> for (PA4<Analog>, PA5<Analog>) {
type Output = (C1, C2);
}

pub fn dac<PINS>(_dac: DAC, _pins: PINS, rcc: &mut Rcc) -> PINS::Output
where
PINS: Pins<DAC>,
PINS: sealed::Pins<DAC>,
{
// Enable DAC clocks
rcc.regs.apb1enr.modify(|_, w| w.dacen().set_bit());
Expand All @@ -114,7 +118,7 @@ where
rcc.regs.apb1rstr.modify(|_, w| w.dacrst().set_bit());
rcc.regs.apb1rstr.modify(|_, w| w.dacrst().clear_bit());

unsafe { mem::uninitialized() }
unsafe { mem::MaybeUninit::uninit().assume_init() }
}

macro_rules! dac {
Expand Down Expand Up @@ -143,13 +147,13 @@ macro_rules! dac {
pub trait DacExt {
fn constrain<PINS>(self, pins: PINS, rcc: &mut Rcc) -> PINS::Output
where
PINS: Pins<DAC>;
PINS: sealed::Pins<DAC>;
}

impl DacExt for DAC {
fn constrain<PINS>(self, pins: PINS, rcc: &mut Rcc) -> PINS::Output
where
PINS: Pins<DAC>,
PINS: sealed::Pins<DAC>,
{
dac(self, pins, rcc)
}
Expand Down