Notes on Type Layouts and ABIs in Rust
Over the years I've found myself with a weird amount of knowledge about how types and ABIs in Rust work, and I wanted to write it all down in one place so that... it's written down in one place. Much of this information can or should be found in the Rust Language Reference and the Rustonomicon.
There are a lot of exotic platforms out there, and C is kinda jacked up from trying to support them all. Some of these distortions are annoying but technically fair, like not defining integers to be two's complement or not defining a byte (char) to be 8 bits, because those captured genuine differences between platforms at the time. Others are more just an artifact from C trying something that ended up being a mistake, like the weird integer size fuzziness and promotion stuff.
A lot of the things C was trying to cope with have largely died off or been relegated to incredibly niche platforms. As such Rust took the opportunity to define more of the properties of the platforms it supports without breaking compatibility with C on those platforms.
