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From: Stefan Monnier <monnier@IRO.UMontreal.CA>
To: Tom Breton <tehom@panix.com>
Cc: 5728@debbugs.gnu.org
Subject: bug#5728: Byte compile doesn't work right on macro
Date: Thu, 08 Apr 2010 16:02:55 -0400	[thread overview]
Message-ID: <jwvk4sindev.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <E1NrMTf-0000f5-TZ@localhost> (Tom Breton's message of "Mon, 15 Mar 2010 22:25:51 -0400")

> When I byte-compile certain code, the results are different than when
> it's not byte-compiled.  It seems to wrongly merge lists.  The one
> unusual thing I was doing with the code is using a macro to generate a
> call to a ctor (as generated by defstruct)

You're victim of a form of "name capture".
E.g. if you rename `a' to `b' in BUG3, the bug disappears.
And if you macroexpand by hand the call to BUG:make-form the bug is
still there.

More to the point, the bug is in the compiler-macro for
BUG:make-structure:

   ELISP> (compiler-macroexpand '(BUG:make-structure :edits (cons (car a) (BUG:structure->edits cand)) :a nil))
   (block BUG:make-structure
     (vector 'cl-struct-BUG:structure
   	  (cons (car nil) (BUG:structure->edits cand))
   	  nil))
   ELISP> (defsubst* toto (a1 a2) (+ a1 a2))
   toto
   ELISP> (compiler-macroexpand '(toto a2 nil))
   (block toto (+ nil nil))
   
   ELISP> 

The problem is that cl-defsubst-expand does the substitution "a1 -> a2
and a2 -> nil" one after the other rather than simultaneously.

I've just installed a fix for it in the emacs-23 branch.


        Stefan






      reply	other threads:[~2010-04-08 20:02 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-03-16  2:25 bug#5728: Byte compile doesn't work right on macro Tom Breton
2010-04-08 20:02 ` Stefan Monnier [this message]

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