Subject: bug#50043: 28.0.50; USABLE_SIGOI undef code paths do not work correctly

From: Lars Ingebrigtsen <[email-masked]>
Date: Fri, 13 Aug 2021 13:56:40 +0200

To reproduce the problem on Debian (at least), edit src/config.h to
this:

/* Define to 1 if SIGIO is usable. */
/* #define USABLE_SIGIO 0 */

Then recompile Emacs and say

(let ((value 'SECONDARY)
      (x-selection-timeout 2000))
  ;;; from org-get-x-clipboard in lisp/org-compat.el
  (gui-get-selection value 'UTF8_STRING)
  (gui-get-selection value 'COMPOUND_TEXT)
  (gui-get-selection value 'STRING)
  (gui-get-selection value 'TEXT))

This will hang for two seconds instead of returning immediately if
USABLE_SIGIO is defined.

Now, we have SIGIO on almost all supported platforms.  The only ones
that have it disabled might be these ones:

  hpux* | nacl | solaris | unixware )
    emacs_broken_SIGIO=yes

Which is probably why this hasn't been reported more.  (See bug#29170.)

So this isn't exactly a high impact problem, but it should be fixed
anyway.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no