bug#19576: write-file writes the wrong buffer

[martin rudalics]

> about a year ago I reported that `write-file' sometimes writes the wrong
> buffer to the destination file. Unfortunately, I had no feedback regarding
> this. When I checked today, the bug is still there.

Sorry.  I could have sworn we fixed that then.

> The problem occurs when a function on the hook
> `window-size-change-functions' change the current buffer. The functions in
> this hook are executed when `y-or-n-p' is called, which is used by
> `write-file' to verify that it is OK to overwrite an existing file. One
> such function is `follow-window-size-change' in follow.el.
>
> This problem is not limited to `write-file' -- all functions calling
> `y-or-n-p' are affected by this!
>
> Of course, it would be relatively straight forward to modify the offending
> function (and all other similar functions). However, a more robust solution
> would be for the code that calls the functions on the hook to ensure that
> it isn't derailed when the buffer is changed.
>
> Personally, I don't know that part of the code well enough to do this
> change. Martin, is this something that you could look into, or suggest
> someone who can?

Conceptually it should be easy to do that.  Save/restore current buffer,
selected window and frame.  But Alan (concerned about ‘follow-mode’),
Pip (who unfortunately disappeared) and Eli are currently discussing how
to fix ‘window-size-change-functions’ in various other ways as well.
I'll try to get the fix of this bug applied there too.

martin