[TUHS] Any UNIX With No C In Userland?

[Konstantin Belousov via TUHS]

Sorry for dup, resent from the subscribed address.

On Tue, Mar 04, 2025 at 07:15:42PM -0800, Larry McVoy wrote:
> On Wed, Mar 05, 2025 at 10:54:01AM +1100, Rob Pike wrote:
> > The notion that the struct layout must correspond to the hardware device's
> > layout is about as non-portable as thinking can get.
> 
> I agree but as a side note, I ported Lachman's (nee Convergent I believe)
> TCP/IP stack to ETA-10's Sys V OS and to SCO's v7 or whatever they had.
> Somewhere I have a note book where I laid out in structs every packet
> format with notes about what that packet did, I was learning.
> 
> Not once did I think about packing, the structs somehow just worked on
> the machines I was working on.  Maybe the TCP/IP guys knew about spacing
> in the structs.
> 
> I get it, I was naive, but sometimes the structs work.

All questions about type sizes and alignment, as well as the layout of
structures, are defined by platform ABI.  Any useful compiler for C
would follow ABI, and any non-C compiler hoping to interoperate with
the system libraries, would provide some way to communicate using the ABI.

Then, after some time, but long time ago, all Unix-like systems converged
to just two practically observable ABIs: ILP32 and LP64.  Both of them
require 8bit bytes, byte addressability, natural alignment for the basic
integer types, and equiality of uint8_t/unsigned char, uint16_t/short,
uint32_t/long.

>From there, it is easy to see that e.g. layout of most ip protocol packets
can be trivially written as C structs.  The only trouble there is the
need to align whole incoming packets on suitable boundary, but e.g. for
IP/TCP/UDP the 4-bytes is enough, and most hardware enforces it.