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Re: Problem advising nreverse.


From: Barry Margolin
Subject: Re: Problem advising nreverse.
Date: Tue, 15 Dec 2009 16:12:08 -0500
User-agent: MT-NewsWatcher/3.5.3b3 (Intel Mac OS X)

In article <address@hidden>,
 Sergei Organov <address@hidden> wrote:

> > address@hidden (Pascal J. Bourguignon) writes:
> >
> >> Sergei Organov <address@hidden> writes:
> >>> I still wonder if it's documented somewhere in some manual when
> >>> defadvice doesn't actually work. It seems it is not there in the Elisp
> >>> manual, or did I miss it?
> >>
> >> See: (info "(elisp)Advising Primitives")
> >
> > Well, but I didn't find even single word there describing cases when
> > it does not work to advise a funciton.
> 
> Sorry, my mistake. In fact, this topic does tell about when advice won't
> work, but it tells exactly opposite to what actually happens:
> 
> "Calls to the primitive from Lisp code will take note of the advice, but
> calls from C code will ignore the advice."
> 
> Now, in my case `nreverse' is called from Lisp code, not from C code, so
> according to the manual advice must work, right? And there is no single
> word about differences in behavior due to byte-compiling.

Byte compiling effectively changes it to a call from C code, because the 
byte code is a direct reference to the primitive.  "Called from Lisp 
code" means interpreting Lisp source code, since that indirects through 
the function name, which is where advice is stored.

-- 
Barry Margolin, address@hidden
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***


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