Re: [GSoC] Bourne-shell compiler front-end for Guile

[Efraim Flashner <efraim@flashner.co.il>]

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On Wed, Mar 23, 2016 at 03:05:08PM +0100, Ludovic Courtès wrote:
> Efraim Flashner <efraim@flashner.co.il> skribis:
> 
> > On Mon, 21 Mar 2016 23:27:25 +0100
> > ludo@gnu.org (Ludovic Courtès) wrote:
> >
> >> Hi Efraim,
> >> 
> >> Thanks for your proposal!
> >> 
> >> This project can be pretty fun, I think, and quite rewarding if it
> >> indeed allows us to get rid of a bunch of bootstrap binaries.
> >> 
> >> As I see it, the project covers mostly two areas:
> >> 
> >>   1. Lexing & parsing.  This compiler front-end will need a real parser
> >>      for the Bourne shell syntax, notably semicolon-separated command
> >>      sequences, pipes, brace-delimited blocks, functions, variables, and
> >>      ‘test’ and ‘[’.
> >> 
> >>      The available tools could be SILex + (system base lalr) (the latter
> >>      is part of Guile, the former is maintained separately; a copy can
> >>      be found in Guile-RPC for instance.)
> >> 
> >>   2. Run-time support: redirections, pipes, background execution, C-c
> >>      (SIGINT) and C-z (SIGTSTP), globbing, and so on.
> >> 
> >>      Guile provides just the basic here, and a little more with (ice-9
> >>      popen).  Scsh and its Guile port(s) provide a lot of that, so it
> >>      might be a good idea to see what can be stolen from these.
> >> 
> >> It may be that some of your CS classes cover some of this ground (a
> >> fairly common programming project here at university is to implement a
> >> small shell precisely because it covers several areas.)
> >> 
> >> How does that sound?
> >> 
> >> Perhaps one way to get started would be by looking at the available
> >> tools for #1, and experimenting with hacks for #2, possibly borrowing
> >> code from Scsh.
> >> 
> >> Thoughts?
> >
> > Sounds like lots of fun, I'm really looking forward to it. And it sounds like
> > I'll need to dive deeper into bash to see what I get to implement
> 
> I guess a related question is how confident/familiar you feel with the
> two areas above.  The agenda could be adjusted as a function of that.
> 
> Thanks,
> Ludo’.

I feel pretty confident about the lexing and parsing; not too sure what
would go into implementing the run-time support.

To summarize a bit, there are two mostly overlapping parts here, one more
busybox-esque where we can drop bootstrap binaries, and a second with a
shell implemented in guile. At this stage I have more in the
confidence/excitement side and less on the familiarity side.

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Efraim Flashner   <efraim@flashner.co.il>   אפרים פלשנר
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