bug#16804: 24.3.50; [PATCH] fix with-silent-modifications

[Leo Liu]

On 2014-02-19 12:39 +0800, Stefan Monnier wrote:
> I vaguely understand what kind of problem you're talking about, but not
> precisely enough to guess what kinds of fixes might make sense.

I think the problem is let-binding buffer-file-name and
buffer-file-truename to nil is a really bad idea. I did a grep on
buffer-file-name in lisp/ directory and got about 2000 entries. Code at
distance may run while eval'ing the body of with-silent-modifications
and affected by the nil value of buffer-file-name etc.

>> Any comments on the following fix? Thanks.
>
> I think I'd rather add a new inhibit-<something>, but it's hard to tell
> without knowing more of the problem at hand.

So with-silent-modifications needs another way to achieve its goal. From
reading its in-code comments, it seems it wants to prevent:

        1. create and delete file locks.
        2. change file modtime which could have effect beyond the scope
           of the macro

Leo