bug#25040: 24.5; setting mail-interactive to nil causes error while sending

[Noam Postavsky]

On Sat, Nov 26, 2016 at 7:21 PM, Francesco Potortì <pot@gnu.org> wrote:
> In sendmail.el I find this:
>
> ================
> (defun sendmail-send-it ()
>   "Send the current mail buffer using the Sendmail package.
> This is a suitable value for `send-mail-function'.  It sends using the
> external program defined by `sendmail-program'."
>   (require 'mail-utils)
>   (let ((errbuf (if mail-interactive
>                     (generate-new-buffer " sendmail errors")
>                   0))
> ================
>
> However, the final 0 makes no sense to me, and in fact it generates an
> error when sending mail if mail-interactive is set to nil.
>
> Changing the 0 to nil apparently corrects the problem.

Can you show the error backtrace? It looks like errbuf is unused when
mail-interactive is nil except for the call to call-process-region
where it acts as the BUFFER argument

    Insert output in BUFFER before point; t means current buffer; nil for
     BUFFER means discard it; 0 means discard and don’t wait