Possible miscompilation error?

[vojty]

Hello, I've found a strange error and I'm not sure what the problem might be. I've been trying to use ESP32 + SCD41 with no luck. I tracked down the problem to this piece of code:

// source https://github.com/Sensirion/sensirion-i2c-rs/blob/master/src/crc8.rs#L11-L25
pub fn calculate(data: &[u8]) -> u8 {
    const CRC8_POLYNOMIAL: u8 = 0x31;
    let mut crc: u8 = 0xff;
    for byte in data {
        crc ^= byte;
        for _ in 0..8 {
            if (crc & 0x80) > 0 {
                crc = (crc << 1) ^ CRC8_POLYNOMIAL;
            } else {
                crc <<= 1;
            }
        }
    }
    crc
}

For the given example data [9, 94] the correct result should be 35 but I'm getting 55. It works correctly on the blank Rust project using cargo new but it fails when I deploy the code to my ESP32.

I've created an example here https://wokwi.com/projects/345876589283639891 with 2 identical calculate functions, the only difference is that one of them has println! macros inside. However, the result differs.

Does anyone know what's going on? What am I missing?

[MabezDev]

Duplicate of https://github.com/esp-rs/rust/issues/134