Chain glib's SIGCHLD handler from Emacs's (Bug#14474).

* process.c (dummy_handler): New function.
(lib_child_handler): New static var.
(handle_child_signal): Invoke it.
(catch_child_signal): If a library has set up a signal handler,
save it into lib_child_handler.
(init_process_emacs): If using glib and not on Windows, tickle glib's
child-handling code so that it initializes its private SIGCHLD handler.
* syssignal.h (SA_SIGINFO): Default to 0.
* xterm.c (x_term_init): Remove D-bus hack that I installed on May
31; it should no longer be needed now.

4 files changed, 37 insertions, 9 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 67b1b482f3f..ac0563c6bdd 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,17 @@
+2013-06-05  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Chain glib's SIGCHLD handler from Emacs's (Bug#14474).
+        * process.c (dummy_handler): New function.
+        (lib_child_handler): New static var.
+        (handle_child_signal): Invoke it.
+        (catch_child_signal): If a library has set up a signal handler,
+        save it into lib_child_handler.
+        (init_process_emacs): If using glib and not on Windows, tickle glib's
+        child-handling code so that it initializes its private SIGCHLD handler.
+        * syssignal.h (SA_SIGINFO): Default to 0.
+        * xterm.c (x_term_init): Remove D-bus hack that I installed on May
+        31; it should no longer be needed now.
+
 2013-06-05  Michael Albinus  <michael.albinus@gmx.de>
 
         * emacs.c (main) [HAVE_GFILENOTIFY]: Call globals_of_gfilenotify.
diff --git a/src/process.c b/src/process.c
index 33035078df9..6ae02494d36 100644
--- a/src/process.c
+++ b/src/process.c
@@ -6100,6 +6100,12 @@ process has been transmitted to the serial port.  */)
    might inadvertently reap a GTK-created process that happened to
    have the same process ID.  */
 
+/* LIB_CHILD_HANDLER is a SIGCHLD handler that Emacs calls while doing
+   its own SIGCHLD handling.  On POSIXish systems, glib needs this to
+   keep track of its own children.  The default handler does nothing.  */
+static void dummy_handler (int sig) {}
+static signal_handler_t volatile lib_child_handler = dummy_handler;
+
 /* Handle a SIGCHLD signal by looking for known child processes of
    Emacs whose status have changed.  For each one found, record its
    new status.
@@ -6184,6 +6190,8 @@ handle_child_signal (int sig)
             }
         }
     }
+
+  lib_child_handler (sig);
 }
 
 static void
@@ -7035,9 +7043,13 @@ static
 void
 catch_child_signal (void)
 {
-  struct sigaction action;
+  struct sigaction action, old_action;
   emacs_sigaction_init (&action, deliver_child_signal);
-  sigaction (SIGCHLD, &action, 0);
+  sigaction (SIGCHLD, &action, &old_action);
+  eassert (! (old_action.sa_flags & SA_SIGINFO));
+  if (old_action.sa_handler != SIG_DFL && old_action.sa_handler != SIG_IGN
+      && old_action.sa_handler != deliver_child_signal)
+    lib_child_handler = old_action.sa_handler;
 }
 
 
@@ -7055,6 +7067,11 @@ init_process_emacs (void)
   if (! noninteractive || initialized)
 #endif
     {
+#if defined HAVE_GLIB && !defined WINDOWSNT
+      /* Tickle glib's child-handling code so that it initializes its
+         private SIGCHLD handler.  */
+      g_source_unref (g_child_watch_source_new (0));
+#endif
       catch_child_signal ();
     }
 
diff --git a/src/syssignal.h b/src/syssignal.h
index d7399c6cb8c..45ea8f1af3c 100644
--- a/src/syssignal.h
+++ b/src/syssignal.h
@@ -50,6 +50,10 @@ char const *safe_strsignal (int) ATTRIBUTE_CONST;
 # define NSIG NSIG_MINIMUM
 #endif
 
+#ifndef SA_SIGINFO
+# define SA_SIGINFO 0
+#endif
+
 #ifndef emacs_raise
 # define emacs_raise(sig) raise (sig)
 #endif
diff --git a/src/xterm.c b/src/xterm.c
index 7038de7039f..7505aa3936b 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -9897,13 +9897,6 @@ x_term_init (Lisp_Object display_name, char *xrm_option, char *resource_name)
 
         XSetLocaleModifiers ("");
 
-        /* If D-Bus is not already configured, inhibit D-Bus autolaunch,
-           as autolaunch can mess up Emacs's SIGCHLD handler.
-           FIXME: Rewrite subprocess handlers to use glib's child watchers.
-           See Bug#14474.  */
-        if (! egetenv ("DBUS_SESSION_BUS_ADDRESS"))
-          xputenv ("DBUS_SESSION_BUS_ADDRESS=unix:path=/dev/null");
-
         /* Emacs can only handle core input events, so make sure
            Gtk doesn't use Xinput or Xinput2 extensions.  */
         xputenv ("GDK_CORE_DEVICE_EVENTS=1");