Use tcdrain, not fdatasync, to drain ttys

fdatasync is for storage devices, not ttys.
* admin/merge-gnulib (GNULIB_MODULES): Remove fdatasync.
* lib/fdatasync.c, m4/fdatasync.m4: Remove.
* lib-src/Makefile.in (LIB_FDATASYNC):
* src/Makefile.in (LIB_FDATASYNC):
Remove.  All uses removed.
* lib-src/emacsclient.c [!DOS_NT]:
Include <termios.h>, for tcdrain.
* lib-src/emacsclient.c (flush_stdout):
* src/sysdep.c (reset_sys_modes): On ttys, use tcdrain instead
of fdatasync (except don’t use either function if DOS_NT).
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.

2 files changed, 5 insertions, 6 deletions

diff --git a/src/Makefile.in b/src/Makefile.in
index 2dba1026c34..6b2e54a1602 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -141,7 +141,6 @@ M17N_FLT_LIBS = @M17N_FLT_LIBS@
 LIB_ACL=@LIB_ACL@
 LIB_CLOCK_GETTIME=@LIB_CLOCK_GETTIME@
 LIB_EACCESS=@LIB_EACCESS@
-LIB_FDATASYNC=@LIB_FDATASYNC@
 LIB_TIMER_TIME=@LIB_TIMER_TIME@
 
 DBUS_CFLAGS = @DBUS_CFLAGS@
@@ -496,7 +495,7 @@ LIBES = $(LIBS) $(W32_LIBS) $(LIBS_GNUSTEP) $(LIBX_BASE) $(LIBIMAGE) \
    $(LIBX_OTHER) $(LIBSOUND) \
    $(RSVG_LIBS) $(IMAGEMAGICK_LIBS) $(LIB_ACL) $(LIB_CLOCK_GETTIME) \
    $(WEBKIT_LIBS) \
-   $(LIB_EACCESS) $(LIB_FDATASYNC) $(LIB_TIMER_TIME) $(DBUS_LIBS) \
+   $(LIB_EACCESS) $(LIB_TIMER_TIME) $(DBUS_LIBS) \
    $(LIB_EXECINFO) $(XRANDR_LIBS) $(XINERAMA_LIBS) $(XFIXES_LIBS) \
    $(XDBE_LIBS) \
    $(LIBXML2_LIBS) $(LIBGPM) $(LIBS_SYSTEM) $(CAIRO_LIBS) \
diff --git a/src/sysdep.c b/src/sysdep.c
index ddcb594f668..b054839795b 100644
--- a/src/sysdep.c
+++ b/src/sysdep.c
@@ -1519,19 +1519,19 @@ reset_sys_modes (struct tty_display_info *tty_out)
   if (tty_out->terminal->reset_terminal_modes_hook)
     tty_out->terminal->reset_terminal_modes_hook (tty_out->terminal);
 
+#ifndef DOS_NT
   /* Avoid possible loss of output when changing terminal modes.  */
-  while (fdatasync (fileno (tty_out->output)) != 0 && errno == EINTR)
+  while (tcdrain (fileno (tty_out->output)) != 0 && errno == EINTR)
     continue;
 
-#ifndef DOS_NT
-#ifdef F_SETOWN
+# ifdef F_SETOWN
   if (interrupt_input)
     {
       reset_sigio (fileno (tty_out->input));
       fcntl (fileno (tty_out->input), F_SETOWN,
              old_fcntl_owner[fileno (tty_out->input)]);
     }
-#endif /* F_SETOWN */
+# endif /* F_SETOWN */
   fcntl (fileno (tty_out->input), F_SETFL,
          fcntl (fileno (tty_out->input), F_GETFL, 0) & ~O_NONBLOCK);
 #endif