Ideas for projects in ableC

[remexre]

It might be a good thing to have a realish piece of software written in ableC, as a way to show off ableC, a way to find the "rough spots" in using it, and as a way to find new extensions to write.

I'd propose an ircd for this -- IRC's got simple enough semantics (chat with channels and DMs, no persistent accounts or history or anything) that it should be possible for a student to write one in a month or two in plain C, plus it has lots of places where ableC would be useful:

• Something goroutine-like (could be mcontext_t tasks + channels) would be very useful for concurrency; a simple model would be:
  • one task per channel
  • two tasks per user, one for sending and one for recving
  • two (go-like) channels per user per channel, acting as a single bidirectional one
  • user send task reads the channel messages and sends them over the socket
  • user recv task reads+parses from the socket and sends to the appropriate channel
• The IRC protocol is weird, so a generated parser would be useful!
• The IRC protocol has a small stateful structure, so maybe an extension for state machines would be useful?
• String manipulation and some data structures are involved, so:
  • more readable code!
  • faster code, if we monomorphize+inline (see also, well-written c++/rust are faster than well-written c)
  • being able to say "fewer memory unsafety bugs b/c ableC-{string,vector,map} make making mistakes harder"
• ircds are typically taking untrusted input from the net, so they're a "real example" as far as security-related analyses are concerned.
• I want a new ircd, ngircd's kinda crappy

[ericvanwyk]

This would be good. Any pointers to IRC protocol docs or intro to using IRC? Something that would give someone a place to get started thinking about this.

[remexre]

For an intro to using IRC, https://libera.chat/guides/basics

I'd probably recommend the Libera webchats or Hexchat to someone wanting to try it out; we have #silver on Libera bridged to the Slack channel, so that'd be a reasonable place to try posting a "hello from irc" or whatever. (My current "main" setup is based on Weechat+soju, but Weechat is "power-user-ware...")

For a brutally simple client to study, ii comes in at just under 1k lines of C. I've got a parser for the lexical syntax (in Haskell, using parser combinators) here, though that might not be the most useful. Pretty much every popular programming language has an IRC client library available too. (I'd still recommend reading RFC2810 and RFC2811, they're 29 pages together and describe the semantics pretty well.)

The "It's very simple — you read the protocol and write the code" approach would probably start at RFCs 2810, 2811, and 2812 (the first two are semantics, last is protocol), RFC7194 (just specifies how TLS should work, the answer is "at port 6697" but this requires 3 pages to say), and then consider going on to the IRCv3 specs, which add all the stuff modern chat protocols have, eg typing notifs, replies, reacts, server-side history, etc. All the IRCv3 stuff is optional, clients negotiate which features are enabled with the server, and I'd say probably skip implementing them unless one demonstrates a particular extension we want to show off (e.g. sqlite ext for server-side history).

Depending on the client, it may be possible to see what is being sent and received too; in Weechat (not to be confused with Wechat!) this is /server raw: