Cannot create static HistoryBuffer

[andresv]

With Vec it is possible to do this:

use heapless::Vec; // fixed capacity `std::Vec`
use heapless::consts::U8; // type level integer used to specify capacity
static mut XS: Vec<u8, U8> = Vec(heapless::i::Vec::new());
let xs = unsafe { &mut XS };

However HistoryBuffer is missing in heapless::i.

[birkenfeld]

That's (currently) unavoidable since the T: Default bound can't be used there.

[andresv]

So currently I can create it only to stack?

[korken89]

I will have a look at fixing this, it's was a miss in my review of the HistoryBuffer PR

[korken89]

For now, you can put it in an option as a workaround.

[andresv]

Like this?

#[app(device = hal::stm32, peripherals = true)]
const APP: () = {
    struct Resources {
        ntc: &'static HistoryBuffer<u16, U100>,
    }

    #[init]
    fn init(mut ctx: init::Context) -> init::LateResources {
        // hack to make a static alloc
        static mut NTC: Option<HistoryBuffer::<u16, U100>> = None;
        unsafe {NTC = Some(HistoryBuffer::new())};

        init::LateResources {
            ntc: unsafe {NTC.as_mut().unwrap()},
        }
    }

[korken89]

Ah no, I think this should work with RTFM:

#[app(device = hal::stm32, peripherals = true)]
const APP: () = {
    struct Resources {
        ntc: HistoryBuffer<u16, U100>,
    }

    #[init]
    fn init(mut ctx: init::Context) -> init::LateResources {
        init::LateResources {
            ntc: HistoryBuffer::new(),
        }
    }

[andresv]

Indeed, this is much better.