[Chicken-hackers] [PATCH] Add aggressive debugging checks to squash those damn bugs

[Peter Bex]

Hello all,

As some may (or may not...) have noticed, everything is completely
fucked up: people are getting random errors (#1041, #1045) and a
shitload of eggs is no longer being properly tested on Salmonella due
to random untraceable breakage in henrietta-cache at Alaric's machine
(which for some odd reason does not happen on the call-cc server).

This has been going on for almost a week now, and it calls for some
serious debugging!  Attached are some patches:

The first patch adds assertions to all the type accessors like C_unfix,
C_block_{header,item}, C_character_code etc.  It does this through a
"check" macro which contains a horrible, evil hack which allows LET-like
semantics in C macros, in a bit of a manual way.
If you'd like more info, let me know and I'll try to clarify.  Also, if
anyone knows of a way to do this in a less verbose, ugly way, please let
me know!

The patch also cleans up a few unused macros and ensures all macros
nicely use the C_(set)_block_item, C_block_header and C_data_pointer to
access the C_SCHEME_BLOCK objects.  This cleans up things a bit (and in
this case, ensures the assertions are triggered when things are wrong).

The rest of the patches are fixes for the few broken things I've already
found by running "make check" and one or two egg tests on an instrumented
version of CHICKEN:

- The second patch fixes a subtle problem with the way
   CHICKEN_initialize calls C_randomize; the latter expects a fixnum
   but it's invoked with an unboxed C integer.  This will error out
   every 2 seconds (on odd seconds, it will carry on because these look
   like boxed fixnums at the bit level)
- The third patch fixes several fuckups in the reader related to EOF
   being treated as if it were a character (and then indexing into
   various vectors and shit like that).  I think this may be a fix for
   the bugs Alaric has been running into with henrietta-cache (but I'm
   not 100% sure yet).
  Don't be afraid; the patch is a lot of lines, but mostly reindenting
   caused by a change of a 2-way IF to a 3-way COND.  ediff can
   highlight the non-whitespace changes sanely.
- The fourth patch is another subtle thing which may cause corruption
   in some programs using read-string!, but I doubt this has been
   encountered much in practice because it's 100% reproducible and
   will cause the exact same corruption every time: it'll insert a NUL
   byte at the start of the string buffer passed to read-string!.
  I've added some tests, because it's actually observable.

I know the first patch is pretty large and ugly as hell, but considering
how much this has already found (the above bugs and a bug in the numbers
egg's type DB), I think it's worth embedding this into every DEBUGBUILD.
It should also help if all Salmonella instances run this, as it will help
us pinpoint more hard-to-find bugs.

Of course it will slow down DEBUGBUILD CHICKENs even more (noticably),
but generally a DEBUGBUILD isn't really built for speed, so it shouldn't
matter so much.

Cheers,
Peter
-- 
http://www.more-magic.net

0001-In-DEBUGBUILDs-add-sanity-assertions-to-most-importa.patch
Description: Text document

0002-Fix-CHICKEN_initialize-s-call-to-C_randomize-which-e.patch
Description: Text document

0003-Fix-several-subtle-problems-in-the-reader-caused-by-.patch
Description: Text document

0004-Fix-read-string-behaviour-after-peeking-at-EOF-add-r.patch
Description: Text document