Problem with define-macro from compiled file (Guile 1.9)

Problem with define-macro from compiled file (Guile 1.9)

[Patrick Bernaud]

Hello,

I have a case where a macro is defined in a file that is then loaded
by another which makes use of the macro. And it produces a 'wrong type
to apply' error from the VM.

(Works fine with GUILE_AUTO_COMPILE=0 and compiled files removed).

For example, with the 'when' macro from the manual:

-%<---- when.scm ----%<-
(define-macro (when cond exp . rest)
  `(if ,cond
       (begin ,exp . ,rest)))
-%<---- when.scm ----%<-

-%<---- test.scm ----%<-
(load "when.scm")
(when #t (display "Launching missiles!\n"))
-%<---- test.scm ----%<-

I get:

$ guile -s test.scm
Launching missiles!
Backtrace:
In ice-9/boot-9.scm:
 170: 9 [catch #t #<catch-closure 8ebb2c0> ...]
In unknown file:
   ?: 8 [catch-closure]
In ice-9/boot-9.scm:
  62: 7 [call-with-prompt prompt0 ...]
In ice-9/eval.scm:
 389: 6 [eval # #]
In ice-9/boot-9.scm:
1863: 5 [save-module-excursion #<procedure 8f0dc90 at ice-9/boot-9.scm:1877:3 ()>]
1171: 4 [load "test.scm" #f]
In unknown file:
   ?: 3 [load-compiled/vm "/home/pat/.cache/guile/ccache/2.0-0.T-LE-4/home/pat/devel/guile/test.scm.go"]
In test.scm:
   2: 2 [#<procedure 8e835a0 ()>]
In ice-9/boot-9.scm:
 115: 1 [#<procedure 8e354d8 at ice-9/boot-9.scm:110:6 (thrown-k . args)> wrong-type-arg ...]
In unknown file:
   ?: 0 [catch-closure wrong-type-arg #f ...]

ERROR: In procedure catch-closure:
ERROR: Wrong type to apply: #<syntax-transformer when>
$

Am I doing wrong something wrong?

Regards,


Patrick

Re: Problem with define-macro from compiled file (Guile 1.9)

[Ludovic Courtès]

Hi,

Patrick Bernaud <patrickb@chez.com> writes:

> -%<---- when.scm ----%<-
> (define-macro (when cond exp . rest)
>   `(if ,cond
>        (begin ,exp . ,rest)))
> -%<---- when.scm ----%<-
>
> -%<---- test.scm ----%<-
> (load "when.scm")
> (when #t (display "Launching missiles!\n"))
> -%<---- test.scm ----%<-

[...]

> ERROR: In procedure catch-closure:
> ERROR: Wrong type to apply: #<syntax-transformer when>

This is because ‘when’ wasn’t expanded in ‘test.scm’, because its
definition wasn’t visible at the time ‘test.scm’ was compiled (remember
that ‘load’ is something that happens at run time.)

Thus the compiler assumed that ‘when’ is a global variable, leading to
the error above (compiling ‘test.scm’ with ‘guile-tools compile
-Wunbound-variable’ should have given a warning.)

The solution is to get rid of ‘load’: either use ‘(include "when.scm")’,
or turn ‘when.scm’ into a module and use it in ‘test.scm’.

Thanks,
Ludo’.

Re: Problem with define-macro from compiled file (Guile 1.9)

[Hans Aberg]

On 6 Jan 2011, at 19:18, Patrick Bernaud wrote:

> I have a case where a macro is defined in a file that is then loaded
> by another which makes use of the macro. And it produces a 'wrong type
> to apply' error from the VM.
>
> (Works fine with GUILE_AUTO_COMPILE=0 and compiled files removed).
>
> For example, with the 'when' macro from the manual:
>
> -%<---- when.scm ----%<-
> (define-macro (when cond exp . rest)
> `(if ,cond
>      (begin ,exp . ,rest)))
> -%<---- when.scm ----%<-
>
> -%<---- test.scm ----%<-
> (load "when.scm")
> (when #t (display "Launching missiles!\n"))
> -%<---- test.scm ----%<-

If you are writing your own macro, I find 'define-syntax' easier:

(use-syntax (ice-9 syncase))

(define-syntax when
  (syntax-rules ()
    ((when cond x ...)
      (if cond (begin x ...)))
))

(when #t (display "Launching missiles!\n"))

Re: Problem with define-macro from compiled file (Guile 1.9)

[Andreas Rottmann]

Hans Aberg <haberg-1@telia.com> writes:

> On 6 Jan 2011, at 19:18, Patrick Bernaud wrote:
>
>> I have a case where a macro is defined in a file that is then loaded
>> by another which makes use of the macro. And it produces a 'wrong type
>> to apply' error from the VM.
>>
>> (Works fine with GUILE_AUTO_COMPILE=0 and compiled files removed).
>>
>> For example, with the 'when' macro from the manual:
>>
>> -%<---- when.scm ----%<-
>> (define-macro (when cond exp . rest)
>> `(if ,cond
>>      (begin ,exp . ,rest)))
>> -%<---- when.scm ----%<-
>>
>> -%<---- test.scm ----%<-
>> (load "when.scm")
>> (when #t (display "Launching missiles!\n"))
>> -%<---- test.scm ----%<-
>
> If you are writing your own macro, I find 'define-syntax' easier:
>
> [...]

It's not only easier, it also not inherently broken (as `define-macro'
is).  See <http://en.wikipedia.org/wiki/Hygienic_macro> for a discussion
of the hygiene issue.

For example, the following invocation of `when' will break when
implemented with `define-macro' as above:

(let ((begin #f))
  (when #t
    (display "Launching missiles!\n")))

Regards, Rotty
-- 
Andreas Rottmann -- <http://rotty.yi.org/>

Re: Problem with define-macro from compiled file (Guile 1.9)

[Hans Aberg]

On 8 Jan 2011, at 00:22, Andreas Rottmann wrote:

>> If you are writing your own macro, I find 'define-syntax' easier:
>
> It's not only easier, it also not inherently broken (as `define-macro'
> is).  See <http://en.wikipedia.org/wiki/Hygienic_macro> for a  
> discussion
> of the hygiene issue.

This is a good discussion. I need introducing local variables in the  
macro definition, which 'define-macro' resolves. So thanks!

Predicate of define-syntax

[Hans Aberg]

On 8 Jan 2011, at 00:22, Andreas Rottmann wrote:

>> If you are writing your own macro, I find 'define-syntax' easier:
>
> It's not only easier, it also not inherently broken (as `define-macro'
> is).  See <http://en.wikipedia.org/wiki/Hygienic_macro> for a  
> discussion
> of the hygiene issue.

It seems that one cannot check that it is a macro, though. For some  
reason, they do not self-evaluate.


(macro? cond)
   ~> #t


(define-syntax def
   (syntax-rules ()
     ((def x ...)
       (define x ...))
))

(macro? def)
   ~> error