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, 9 insertions, 5 deletions

diff --git a/lib-src/Makefile.in b/lib-src/Makefile.in
index ecb9208a1cd..00151933caa 100644
--- a/lib-src/Makefile.in
+++ b/lib-src/Makefile.in
@@ -204,8 +204,6 @@ LIBRESOLV=@LIBRESOLV@
 LIBS_MAIL=@LIBS_MAIL@
 ## empty or -lrt or -lposix4 if HAVE_CLOCK_GETTIME
 LIB_CLOCK_GETTIME = @LIB_CLOCK_GETTIME@
-## empty or -lrt or -lposix4 if HAVE_FDATASYNC
-LIB_FDATASYNC = @LIB_FDATASYNC@
 ## empty or -lwsock2 for MinGW
 LIB_WSOCK32=@LIB_WSOCK32@
 
@@ -396,12 +394,12 @@ pop.o: ${srcdir}/pop.c ${srcdir}/pop.h ${srcdir}/../lib/min-max.h $(config_h)
 
 emacsclient${EXEEXT}: ${srcdir}/emacsclient.c $(NTLIB) $(config_h)
         $(AM_V_CCLD)$(CC) ${ALL_CFLAGS} $< \
-           -DVERSION="\"${version}\"" $(NTLIB) $(LOADLIBES) $(LIB_FDATASYNC) \
+           -DVERSION="\"${version}\"" $(NTLIB) $(LOADLIBES) \
            $(LIB_WSOCK32) $(LIBS_ECLIENT) -o $@
 
 emacsclientw${EXEEXT}: ${srcdir}/emacsclient.c $(NTLIB) $(CLIENTRES) $(config_h)
         $(AM_V_CCLD)$(CC) ${ALL_CFLAGS} $(CLIENTRES) -mwindows $< \
-           -DVERSION="\"${version}\"" $(LOADLIBES) $(LIB_FDATASYNC) \
+           -DVERSION="\"${version}\"" $(LOADLIBES) \
            $(LIB_WSOCK32) $(LIBS_ECLIENT) -o $@
 
 NTINC = ${srcdir}/../nt/inc
diff --git a/lib-src/emacsclient.c b/lib-src/emacsclient.c
index df44bc4087c..1c62c09451c 100644
--- a/lib-src/emacsclient.c
+++ b/lib-src/emacsclient.c
@@ -65,6 +65,10 @@ char *w32_getenv (const char *);
 
 #endif /* !WINDOWSNT */
 
+#ifndef DOS_NT
+# include <termios.h>
+#endif
+
 #include <ctype.h>
 #include <errno.h>
 #include <getopt.h>
@@ -1722,8 +1726,10 @@ static void
 flush_stdout (HSOCKET emacs_socket)
 {
   fflush (stdout);
-  while (fdatasync (STDOUT_FILENO) != 0 && errno == EINTR)
+#ifndef DOS_NT
+  while (tcdrain (STDOUT_FILENO) != 0 && errno == EINTR)
     act_on_signals (emacs_socket);
+#endif
 }
 
 int