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

[martin rudalics]

>> 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