Variable: buffer-offer-save
buffer-offer-save is a customizable and buffer-local variable defined
in files.el.gz.
Documentation
Non-nil in a buffer means always offer to save buffer on exiting Emacs.
Do so even if the buffer is not visiting a file. Automatically local in all buffers.
Set to the symbol always to offer to save buffer whenever
save-some-buffers is called.
Note that this option has no effect on kill-buffer;
if you want to control what happens when a buffer is killed,
use kill-buffer-query-functions.
Probably introduced at or before Emacs version 18.
Source Code
;; Defined in /usr/src/emacs/lisp/files.el.gz
(defcustom buffer-offer-save nil
"Non-nil in a buffer means always offer to save buffer on exiting Emacs.
Do so even if the buffer is not visiting a file.
Automatically local in all buffers.
Set to the symbol `always' to offer to save buffer whenever
`save-some-buffers' is called.
Note that this option has no effect on `kill-buffer';
if you want to control what happens when a buffer is killed,
use `kill-buffer-query-functions'."
:type '(choice (const :tag "Never" nil)
(const :tag "On Emacs exit" t)
(const :tag "Whenever save-some-buffers is called" always))
:group 'backup)