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[Chicken-hackers] [PATCH] Fix line numbers in error messages inside modu

From: Peter Bex
Subject: [Chicken-hackers] [PATCH] Fix line numbers in error messages inside modules
Date: Sun, 6 May 2012 21:37:32 +0200
User-agent: Mutt/

Hi hackers,

While working on some code I noticed that all error messages of code
that goes wrong inside modules always show the line number of the
module definition's start.  This is really annoying, especially in
large modules this doesn't help (and most code nowadays is in modules).


$ cat /tmp/test.scm
(module foo (bar)
  (import chicken scheme)

  (define (bar)
    (print (+ 'a 1))))

(import foo)
$ csc -scrutinize /tmp/test.scm

Warning: in toplevel procedure `foo#bar':
  (/tmp/test.scm:1) in procedure call to `+', expected argument #1 of type 
`number', but was given an argument of type `symbol'

$ /tmp/test

Error: (+) bad argument type: a

        Call history:

        /tmp/test.scm:8: foo#bar          
        /tmp/test.scm:1: +              <--

As you can see, all references to "+" mention line 1, while the actual
code is several lines lower (line 5).

The reason this happens is that the compiler strips all syntax off
entire modules and then walks the contents, which means all contents
have been copied to fresh cons cells, while the line number database
holds the old cons cells.

Besides this annoying aspect, I think stripping entire modules is bad
practice.  If anything goes wrong by not stripping them, we should fix
that properly (by fixing the syntax env or wherever it goes wrong).
However, we don't have a single test that fails when not stripping them!
Compilation should also be faster by not running strip-syntax over
entire modules.

The attached patch removes this stripping of modules and adds a
regression test.  All core tests still succeed.  I've also installed
the s48-modules egg and ran its tests, since this is probably the most
complex example that we have of mixing modules and macros.

"The process of preparing programs for a digital computer
 is especially attractive, not only because it can be economically
 and scientifically rewarding, but also because it can be an aesthetic
 experience much like composing poetry or music."
                                                        -- Donald Knuth

Attachment: 0001-Ensure-error-messages-carry-their-line-numbers-corre.patch
Description: Text document

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