[TUHS] Re: Any UNIX With No C In Userland?

On Mon, Mar 3, 2025 at 3:26 PM Steve Nickolas <usotsuki(a)buric.co> wrote: There are a few different ways to do that; some compilers have `#pragma pack(1)` to pack structs on byte boundaries. All are language extensions. Standard C, starting with (IIRC) C11, has the `_Alignas` keyword that lets you specify extended alignment for data; this can be useful in a struct or something. However, I just checked the latest C spec and it's quite explicit that you can't use it to relax alignment requirements to something less strict. That is, you can't portably say `alignas(1)` for an `int`. What Paul described from BLISS makes it sound like you could describe things like an IPv4 packet (which has fields that start at odd bit boundaries) exactly. That's neat. However, usually when programming at _that_ low of a level in C or Rust or something like that, you have an ABI you can rely on for guarantees about the size and alignment of fundamental types. If I'm porting to another machine, I have to be sure those assumptions hold on the target, or update as needed. I guess that's a bummer. Unix got away with being able to specify things the way it did for so long because they controlled the horizontal and the vertical: the compiler was symbiotic with the system. You knew that your C struct looked like the layout of the hardware registers for some device because you maintained the compiler in the same source tree. Those days are long gone, of course, hence much of the current consternation around portable C. - Dan C.