[Ecls-list] Macro+segfault insight appreciated

[Matthew Mondor]

On Sat, 1 May 2010 14:44:02 -0400
Matthew Mondor <mm_lists at pulsar-zone.net> wrote:

> ;;; Here is a second variant using INTERN instead of GENSYM:
> (defmacro defsyscall ((fsymbol cfunction) (&rest cargtypes) documentation)
>   (let* ((nargs (length cargtypes))
> 	 (args (loop
> 		  for i from 0 below nargs
> 		  collect (intern (format nil "ARG~D" i))))
> 	 (cargs (let ((s (with-output-to-string (s)
> 			   (loop
> 			      for i from 0 below nargs
> 			      do (format s "#~D " i)))))
> 		  (subseq s 0 (1- (length s))))))
>     `(defun ,fsymbol ,args
>        ,documentation
>        (ffi:clines "#include <errno.h>")
>        (let ((err (c-inline2 ,args
> 			     ,cargtypes
> 			     :int
> 			     ,(format nil "
> {
> 	if (~A(~A) == 0)
> 		@(return) = 0;
> 	else
> 		@(return) = errno;
> }"
> 				      cfunction
> 				      cargs)
> 			     :one-liner nil)))
> 	 (if (= 0 err)
> 	     nil
> 	     (unix-error ,cfunction err (list , at args))))))) ; Problem using ARGS

Hmm after doing more tests, I noticed that interestingly, replacing the
unix-error call by:

(unix-error ,cfunction err (list ,@(mapcar #'identity args)))

Appears to finally work fine, although:

(unix-error ,cfunction err (list ,@(append args)))

Also doesn't (as well as various tests using APPLY and/or SYMBOL-VALUE).
I'm still interested if someone wishes to explain why :)

Thanks,
-- 
Matt