Re: Upcoming 23.1 release

[Chong Yidong]

Eli Zaretskii <address@hidden> writes:

> Can't we have a magically-named buffer-local variable for the same
> effect in fileio.c?  Then previous behavior would be left untouched,
> and we won't need that much testing, as only Rmail would be affected.

This approach seems wrong anyhow.  Firstly, it prevents Emacs from
disabling auto-saving due to big changes in the file, which could be
either due to buffer swapping or actual changes---and the latter case
can lead to data loss anyway.  Secondly, because of Rmail-mbox's funky
buffer-swapping design, it's not even clear to me that turning on
auto-save-mode manually in Rmail leads to the correct buffer being
auto-saved.

I think the correct fix is to change `buffer-swap-text', giving it an
optional argument that makes it swap the two buffers' values of
auto-save-file-name and auto_save_modified (and possibly other
file-related variables also).  And we need an additional hook into
auto-save-mode that Rmail can use to ensure that M-x auto-save-mode
turns on auto-save in the correct buffer.