Non-unsafe functions for PODs?

[nabijaczleweli]

Since PODs (and only PODs) are actually safe to type-pun we could probably totally do that!

Now if only there was a std::is_pod<T> in Rust…

[nabijaczleweli]

Turns out not even PODs are safe! Great!

[Enet4]

Better permalink.

I suggest that we attempt to grab as many situations of safe transmutation as possible in a case-by-case basis. In particular:

• integer type (u8, i8, u16, i16, u32, i32, u64, i64, u128, i128), bool, char, or float types (f32, f64) to another integer type is safe because all possible bit states are valid integer values;
• the same to f32 or f64 is also safe if we assume that transmuting to signalling NaNs are a no-problem. This isn't 100% agreed on, though, because certain changes in LLVM implementation details could influence this safety (see rust/#39271). On the safe side, we could probably have a function that guards, transmutes and then masks the signalling bits.
• To bool, we could first transmute to u8, check whether each byte is either 0 or 1, and raise an error otherwise.

It's likely that we'll need separate functions for each case.

[nabijaczleweli]

Released in v0.5.0.