Subject: Emacs daemon initialization should not ignore I/O errors

From: Paul Eggert <[email-masked]>
Date: Sun, 20 Mar 2011 16:34:22 -0700

Severity: minor

daemon-initialized currently ignores I/O errors when setting
up the daemon, but it should report them, on the off chance that
system resources are low so that (for example) one cannot open
/dev/null or dup a file descriptor.  I plan to install the following
patch in the trunk, to address this.

2011-03-20  Paul Eggert  <[email-masked]>

	* emacs.c (Fdaemon_initialized): Do not ignore I/O errors.

--- src/emacs.c	2011-03-17 16:32:03 +0000
+++ src/emacs.c	2011-03-20 21:03:44 +0000
@@ -2312,6 +2312,7 @@
   (void)
 {
   int nfd;
+  int err = 0;
 
   if (!IS_DAEMON)
     error ("This function can only be called if emacs is run as a daemon");
@@ -2324,10 +2325,11 @@
 
   /* Get rid of stdin, stdout and stderr.  */
   nfd = open ("/dev/null", O_RDWR);
-  dup2 (nfd, 0);
-  dup2 (nfd, 1);
-  dup2 (nfd, 2);
-  close (nfd);
+  err |= nfd < 0;
+  err |= dup2 (nfd, 0) < 0;
+  err |= dup2 (nfd, 1) < 0;
+  err |= dup2 (nfd, 2) < 0;
+  err |= close (nfd) != 0;
 
   /* Closing the pipe will notify the parent that it can exit.
      FIXME: In case some other process inherited the pipe, closing it here
@@ -2336,10 +2338,13 @@
      Instead, we should probably close the pipe in start-process and
      call-process to make sure the pipe is never inherited by
      subprocesses.  */
-  write (daemon_pipe[1], "\n", 1);
-  close (daemon_pipe[1]);
+  err |= write (daemon_pipe[1], "\n", 1) < 0;
+  err |= close (daemon_pipe[1]) != 0;
   /* Set it to an invalid value so we know we've already run this function.  */
   daemon_pipe[1] = -1;
+
+  if (err)
+    error ("I/O error during daemon initialization");
   return Qt;
 }