GNU bug report logs - #18203
24.4.50; `ffap-url-p' should NOT be a defsubst

Previous Next

Full log

Message #15 received at 18203 <at> debbugs.gnu.org (full text, mbox):

From: Drew Adams <drew.adams <at> oracle.com>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 18203 <at> debbugs.gnu.org
Subject: RE: bug#18203: 24.4.50; `ffap-url-p' should NOT be a defsubst
Date: Fri, 25 Dec 2015 14:44:16 -0800 (PST)

> > There is NO reason for this to be a defsubst.  There is no reason for
> > users not to take advantage of this function generally.
> 
> I changed it to a defun,

Thank you.

> but I don't know what you mean by "There is no
> reason for users not to take advantage of this function generally.".
> You can use a defsubst just as you would a defun.

No, you cannot.

If existing code invokes a defsubst and you have only the compiled
version of that code, then you have no access to the function
defined by that defsubst.  The function _does not exist_ at runtime.
You cannot advise it or debug it, and redefining it has no effect.

Taking advantage of the function _"generally"_ includes having it
available at runtime - it requires its existence _as a function_.

`defsubst's are almost a misfeature nowadays.  In any case, they
be used should rarely, and only with good justification.

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.