Improve on transmute for bindgen structs

[ericseppanen]

Is there a way to improve upon this?

    // Initialize an all-zeros ControlFileData struct
    pub fn new() -> ControlFileData {
        let controlfile: ControlFileData;

        let b = [0u8; SIZEOF_CONTROLDATA];
        controlfile = unsafe {
            std::mem::transmute::<[u8; SIZEOF_CONTROLDATA], ControlFileData>(b)
        };

        return controlfile;
    }
}

Ideally we could have some automatically derived functions that convert to/from [u8].

[ericseppanen]

Rust-bindgen has an open issue on this.

Notes to refresh my memory in the future:

• transmute into structs that are repr(C) are well-defined, so long as the members are also well-defined.
• transmute into u8..u64 and i8..`i64' are well-defined (but malicious values can have weird side-effects).
• transmute into floating-point values is well-defined, but might need to watch out for Signaling NaN values.
• transmute into bool is undefined behavior if the source byte is not 0 or 1.
• transmute into a fixed-size array is well-defined.
• Everything else is probably undefined and dangerous.

[ericseppanen]

The CheckPoint and ControlFileData structs contain bool members, and could be used to trigger undefined behavior if we use transmute.

:(

[lubennikovaav]

Any ideas on how to do it correctly?
We can always serialize it manually, using get_u32_le() functions, as I did in the first version. The only problem I see with this approach is the need to write and support extra code.

[ericseppanen]

I forgot that I had filed this. I think this conversation has moved to issue #6.