Work around glib messing with signal handlers more than it should

* src/process.c (init_process_emacs): force glib's g_unix_signal
handler into lib_child_handler where it should belong.

Copyright-paperwork-exempt: yes

1 files changed, 21 insertions, 5 deletions

diff --git a/src/process.c b/src/process.c
index 50c425077a9..bf64ead24e5 100644
--- a/src/process.c
+++ b/src/process.c
@@ -8217,13 +8217,29 @@ init_process_emacs (int sockfd)
   if (!will_dump_with_unexec_p ())
     {
 #if defined HAVE_GLIB && !defined WINDOWSNT
-      /* Tickle glib's child-handling code.  Ask glib to wait for Emacs itself;
-         this should always fail, but is enough to initialize glib's
+      /* Tickle glib's child-handling code.  Ask glib to install a
+         watch source for Emacs itself which will initialize glib's
          private SIGCHLD handler, allowing catch_child_signal to copy
-         it into lib_child_handler.  */
-      g_source_unref (g_child_watch_source_new (getpid ()));
-#endif
+         it into lib_child_handler.
+
+         Unfortunatly in glib commit 2e471acf, the behavior changed to
+         always install a signal handler when g_child_watch_source_new
+         is called and not just the first time it's called.  Glib also
+         now resets signal handlers to SIG_DFL when it no longer has a
+         watcher on that signal.  This is a hackey work around to get
+         glib's g_unix_signal_handler into lib_child_handler.  */
+      GSource *source = g_child_watch_source_new (getpid ());
+      catch_child_signal ();
+      g_source_unref (source);
+
+      eassert (lib_child_handler != dummy_handler);
+      signal_handler_t lib_child_handler_glib = lib_child_handler;
       catch_child_signal ();
+      eassert (lib_child_handler == dummy_handler);
+      lib_child_handler = lib_child_handler_glib;
+#else
+      catch_child_signal ();
+#endif
     }
 
 #ifdef HAVE_SETRLIMIT