Re: [Chicken-users] keyword args not assigned in program.

[Felix]

From: Alan Post <address@hidden>
Subject: [Chicken-users] keyword args not assigned in program.
Date: Sat, 20 Nov 2010 06:59:38 -0700

> I'm dealing with a frustrating bug--I haven't been able to turn it
> into a simple test case.  Will you let me explain what is going on,
> why I haven't been able to make a test case, and then offer advice?
> 
> I have a compiler to convert a PEG grammar to scheme.  In my test
> suite, I have a line:
> 
> <++> tests/run.scm
>   (set! compiler (eval (compile "test.peg")))
> <-->
> 
> The test.peg file references a symbol defined in tests/run.scm, and
> I run the compiler with some sample data:
> 
> <++> tests/run.scm # this test fails!
>   (define (transform #!rest rest #!key key0)
>     (pretty-print rest)
>     key0)
> 
>   (set! compiler (eval (compile "test.peg")))
> 
>   (compiler "a")
> <-->
> 
> The compiler works, it calls |transform|, but the #!key arguments to
> transform are not properly mapped.  |rest| is:
> 
>   (key0: 0 key1: 1)
> 
> but |key0| is:
> 
>   #f
> 
> So my #!rest arguments are seeing the tagged values, but the tagged
> values aren't being assigned to #!key arguments.
> 
> That is simple enough to diagnose.  I've made my |test.peg| file,
> the one I'm compiling, as simple as possible.  I want to remove the
> compiler, because it is hands down the largest part of the test.
> 
> I run |(compile "teg.peg")| and save the output to |"out.scm"|,
> converting my test to this:
> 
> <++> tests/run.scm # this test works!
>   (define (transform #!rest rest #!key key0)
>     (pretty-print rest)
>     key0)
> 
>   (call-with-output-file "out.scm"
>     (lambda (port)
>       (write (compile "test.peg") port)))
>   (set! compiler (eval (call-with-input-file "out.scm" read)))
> 
>   (compiler "a")
> <-->
> 
> I have a temporary file that I write and then read.  The output of
> the compiler is the same, but the method that the sexpr is evaluated
> changes to have an intermediate file.
> 
> Suddenly, my test works and |key0| receives the correct value.
> 
> It appears that directly evaluating the result of the compiler causes
> #!key arguments not to be assigned, but if I save that same result
> and read it back in, things work fine.
> 
> What is going on?!  My closest guess is that I have some kind of gc
> problem that I only trigger with a program of a particular size.  I'm
> not sure where to go from here, as the test case is still a few
> thousand lines of code, given that the compiler seems integral to
> the test case.
> 

How do the call-sites of `transform' look? Have you tried to
trace `transform' (using the `trace' egg)? That way you can
see how it is invoked. Don't worry about the GC - you would get
much more weird errors than this.


cheers,
felix