Subject: Re: bug#34765: 26.1; with-temp-buffer should not run buffer-list-update-hook

From: martin rudalics <[email-masked]>
Date: Wed, 24 Apr 2019 09:27:59 +0200

>> Stefan asked me to add a variable 'inhibit-buffer-list-update-hook'
 >> and I came up with the attached.  WDYT?
 >
 > Did he also ask you to remove the inhibit_buffer_hooks flag of the
 > buffer object?  I'd rather prefer that you set that flag for temporary
 > buffers.  In any case, removing the flag will get back the problem
 > with hidden buffers used by coding.c, right?  I don't want to lose
 > that.

FWIW handling of the the inhibit_buffer_hooks flag is unaffected by my
patch.  Note that I special cased the call from 'make-indirect-buffer'
which is the only one that doesn't check that flag.

 > More generally, I don't understand the need for this variable.  If we
 > just want to inhibit the hooks for temporary buffers, we don't need to
 > provide a variable, we can do that internally and unconditionally.
 > The variable assumes there are other legitimate use cases where a Lisp
 > program would want to inhibit the hooks, and that we agree to let Lisp
 > programs do that.  What are those use cases?

I don't know.  The one we care about in the case at hand is that of
'with-temp-buffer' which seems innocuous enough for being used in the
body of a function run by 'buffer-list-update-hook'.  Since that macro
is in subr.el and as such cannnot easily set the inhibit_buffer_hooks
flag, the 'inhibit-buffer-list-update-hook' variable provides a simple
workaround.  But maybe Stefan himself can explain the rationale for
such a variable.  IIUC his main motivation was that by rebinding
'inhibit-buffer-list-update-hook' to nil one can from Lisp relax the
restrictions provided by my patch.

martin