> C and C++ treat uninitialized reads as UB, full stop.
Not true; if it's an object that has its address taken, of a type that does not have a trap representation, then reading it results in an unspecified value and is not UB. Which aligns with what one might naively expect to happen.
This is true of Rust as well since it has a very similar memory model. You just have to explicitly tell the compiler you know what you’re doing in Rust through the unsafe keyword.
So reading an uninitialised u8 is not UB? I found the Rust documentation pretty unclear, u8 does not have a "restricted set of valid values" which suggests it should be ok, but the documentation also says "the only cases in which reading uninitialized memory is permitted are inside unions and in “padding” (the gaps between the fields of a type)".
Not true; if it's an object that has its address taken, of a type that does not have a trap representation, then reading it results in an unspecified value and is not UB. Which aligns with what one might naively expect to happen.