Re: [vile] Spooky action in hs-filt.l

[Thomas Dickey]

On Fri, 1 May 2009, Brendan MacDonell wrote:

> Normally with a little bit of grepping around, I'm able to figure out
> what exactly is going on in the syntax highlighters, but the Haskell
> filter frankly has me stumped. Not only do keywords not appear to be
> loaded when it is compiled as a builtin (at least, no keywords seem to
> be found in either table, with or without modifications to modes.rc,
> filters.rc, or hs.keywords), but using it (again as a builtin) also
> appears to be none-deterministic as to the state when comments are
> handled - some comments are highlighted, while others are not
> depending on the order in which they are entered into the editor.

That's about the point where I'd construct a stripped-down .vilerc
with only the scripting I needed to reproduce the problem, and
then rebuild vile with

        --with-builtin-filters
        --with-trace
        --with-valgrind

and see if valgrind could tell me about some invisible memory corruption.

> Curious as to the cause, I tried to bisect between version 9.7e and
> 9.7p in my local git repository, only to discover that patch e seems
> to be functionally equivalent. The strangest thing is that compiling
> hs-filt.l as an external filter and running it manually seems to yield
> the correct results, whether with or without -vv, and piping the
> output through atr2ansi yields the expected keyword-highlighted
> outcome. Frankly I'm at a loss to explain exactly why this is, much
> less to begin debugging it, so I'd be interested to know if anyone
> else has this problem (maybe it's a corner case of my
> flex|reflex/compiler/arch/etc. combo?), or if anyone can explain
> what's going on with it to me.

It could be a problem outside the filter - though at the moment the only 
issue _I_ have found appears in the spell-filter on windows (and I was 
just setting off to see if I could trap it).

Bear in mind that the builtin-filter interface differs subtly from
the extern-filter interface.  Usually it's the same...

--
Thomas E. Dickey
http://invisible-island.net
ftp://invisible-island.net