Idea / Pre-RFC: Null-free pointer and Zeroable reference

Hello,

Just my 2 cents on this, I implemented the bootloader for the MCU with program RAM at address 0x0. I will probably update my implementation to use read_volatile now. might be that this did not work when I first wrote this or I simply missed the option. Both options used in this code snippet work just fine:

#[entry]
fn main() -> ! {
    (...)

    #[allow(clippy::zero_ptr)]
    let first_four_bytes_volatile_read = unsafe { core::ptr::read_volatile(0x0000_0000 as *const u32) }.to_ne_bytes();

    let mut buf: [u8; 4] = [0; 4];
    read_four_bytes_at_addr_zero(&mut buf);

    assert_eq!(first_four_bytes_volatile_read, buf);
}

fn read_four_bytes_at_addr_zero(buf: &mut [u8; 4]) {
    #[allow(clippy::zero_ptr)]
    unsafe {
        core::arch::asm!(
            "ldr r0, [{0}]",    // Load 4 bytes from src into r0 register
            "str r0, [{1}]",    // Store r0 register into first_four_bytes
            in(reg) 0x0 as *const u8,         // Input: src pointer (0x0)
            in(reg) buf as *mut [u8; 4],  // Input: destination pointer
        );
    }
}

On the RFC: I am happy with the way this is now without requiring special language level support, especially now that I know I can use a volatile read for that special case in my bootloader (no assembly required). I have not read all the discussion, but the gist seems to be that this feature is not worth the drawbacks it would mean, especially because there are solutions for them.