[slim-vim] More details on the socket crash bug

[Larry Clapp]

On Mon, Jun 12, 2006 at 07:34:52AM -0400, Larry Clapp wrote:
> On Sun, Jun 11, 2006 at 03:20:09PM -0700, Brad Beveridge wrote:
> > A quick recap - the bug is this:  When you evaluate a form on
> > Swank it send back a reply via a socket.  In Slim-vim we listen on
> > that socket and print some data out to a Vim buffer.  Eventually
> > this crashes and leaves you with a broken console (keystrokes
> > don't appear).  I can blindly issue (cl-user::quit) and get to a
> > bash prompt, I then need to "reset" the terminal.
> > 
> > I spent today trying to reproduce the bug (see attached files for
> > my attempt).  Serverstream just listens on a socket and prints
> > data to a buffer, test.lisp sends data to serverstream.  I run
> > these files in different Vims so that I can have 2 instances of
> > ECL.
> > 
> > I could not break this simple configuration, TEST can happily
> > stream loads of data to SERVERSTREAM, which dutifully puts it out
> > to a Vim buffer.  This implies to me writing to a Vim buffer from
> > the Async handler is completely fine.
> > 
> > So I had a bit of a brain storm and thought about what is
> > different between my test and Swank.  Well, the test is kinda one
> > way, Swank starts comms in Vim and responds to them in Vim.  So I
> > made the SERVERSTREAM also echo back any socket data to the TEST
> > client.  Whoa!  It breaks.
> 
> I haven't tried your code yet, but I noticed this
> 
>   (defmethod si::stream-write-string ((stream vim-buffer-output-stream) string &optional start end)
>     (append-lines (subseq string start end) (buffer-of stream)))
> 
> If START is NIL, subseq will throw an error.  Just a thought.

Okay, I tried your code, and I observed the following behavior:

In test.lisp,

  (progn
    (dotimes (x 10)
      (format *stream* "hello ~D~%" x)))

printed these lines in the serverstream lisp scratch buffer:

  "hello 0"
  "hello 1"
  "hello 2"
  "hello 3"
  "hello 4"
  "hello 5"
  "hello 6"
  "hello 7"
  "hello 8"
  "hello 9"

but printed only

  "\"hello 0\""
  "\"hello 1\""

(or up to 0, or 3, or 7, but rarely if ever the whole 10 lines) in the
test.lisp lisp scratch buffer, until I pressed at least two keys.  I'd
press one key (e.g. "h"), and the rest of the lines would show up.
I'd press it again, and the cursor would show back up in the test.lisp
buffer.  Funky.

I would suggest the following methodology, testing at each step, and
saving snapshots at the end of each step: 1) get the client (test) /
server (serverstream) code to work in ECL only (not run under Vim)
just to make sure you have the plain networking code working.  2)
Import the server code into Vim; have it talk to the ECL-only client.
3) Change the client code to write to a string.  4) Import the client
code into Vim; have it talk to the ECL-only server.  5a) test the
vim-buffer-output-stream apart from the client/server code; 5b) change
the client code to append to a Vim buffer.  6) Change the client code
to talk to the Vim server.

I may do some work on this, or I may adapt some of my own Vim
networking code to work with sb-bsd-sockets, and try that.

-- Larry