Fix emacsclient hang when backgrounded

Problem reported by Kaushal Modi in:
https://lists.gnu.org/r/emacs-devel/2018-12/msg00083.html
The tcdrain call replaced an fdatasync call which had no
effect on the tty, so removing it entirely shouldn’t cause
problems.  The fdatasync call replaced an fsync call which
also had no effect on the tty, and the fsync call seems to be
badly-merged revenant of emacsclient’s old (circa 2004) way of
communicating to and from Emacs via FILE * streams, where
fsync was apparently needed when talking to sockets.
* lib-src/emacsclient.c [!DOS_NT]: Don’t include termios.h.
(flush_stdout): Remove.  All callers removed.
(main): Do not drain the tty after "Waiting for Emacs..."
message.  There should be no need to drain, and draining it
might send us a SIGTTOU.  Do not fflush stdout just before
exiting, as exiting does that for us.

diff --git a/lib-src/emacsclient.c b/lib-src/emacsclient.c
index 7de366511431cfbab633bf7104d0b2217312c64c..653ab955df5eba5ad02138c3a3003c5108f5ea58 100644 (file)
--- a/lib-src/emacsclient.c
+++ b/lib-src/emacsclient.c
@@ -66,10 +66,6 @@ char *w32_getenv (const char *);
 
 #endif /* !WINDOWSNT */
 
-#ifndef DOS_NT
-# include <termios.h>
-#endif
-
 #include <ctype.h>
 #include <errno.h>
 #include <getopt.h>
@@ -1740,15 +1736,6 @@ start_daemon_and_retry_set_socket (void)
   return emacs_socket;
 }
 
-/* Flush standard output and its underlying file descriptor.  */
-static void
-flush_stdout (HSOCKET emacs_socket)
-{
-  fflush (stdout);
-  while (tcdrain (STDOUT_FILENO) != 0 && errno == EINTR)
-    act_on_signals (emacs_socket);
-}
-
 int
 main (int argc, char **argv)
 {
@@ -1964,7 +1951,7 @@ main (int argc, char **argv)
       printf ("Waiting for Emacs...");
       skiplf = false;
     }
-  flush_stdout (emacs_socket);
+  fflush (stdout);
 
   /* Now, wait for an answer and print any messages.  */
   while (exit_status == EXIT_SUCCESS)
@@ -2067,7 +2054,6 @@ main (int argc, char **argv)
 
   if (!skiplf)
     printf ("\n");
-  flush_stdout (emacs_socket);
 
   if (rl < 0)
     exit_status = EXIT_FAILURE;