31 files changed, 404 insertions, 172 deletions

diff --git a/admin/merge-gnulib b/admin/merge-gnulib
index d4bbf17cb3d..85921ba1ba6 100755
--- a/admin/merge-gnulib
+++ b/admin/merge-gnulib
@@ -40,7 +40,7 @@ GNULIB_MODULES='
   sig2str socklen stat-time std-gnu11 stdalign stddef stdio
   stpcpy strftime strtoimax symlink sys_stat
   sys_time time time_r time_rz timegm timer-time timespec-add timespec-sub
-  update-copyright utimens
+  update-copyright unlocked-io utimens
   vla warnings
 '
 
diff --git a/admin/unidata/unidata-gen.el b/admin/unidata/unidata-gen.el
index e1e896ce29c..478099c831a 100644
--- a/admin/unidata/unidata-gen.el
+++ b/admin/unidata/unidata-gen.el
@@ -1346,50 +1346,56 @@ Property value is a symbol `o' (Open), `c' (Close), or `n' (None)."
              (generator (unidata-prop-generator proplist))
              (default-value (unidata-prop-default proplist))
              (val-list (unidata-prop-val-list proplist))
-             (table (progn
-                      (message "Generating %S table..." prop)
-                      (funcall generator prop index default-value val-list)))
-             (decoder (char-table-extra-slot table 1))
-             (alist (and (functionp index)
-                         (funcall index)))
-             (check #x400))
-        (dolist (e unidata-list)
-          (let* ((char (car e))
-                 (val1
-                  (if alist (nth 1 (assoc char alist))
-                    (nth index e)))
-                 val2)
-            (if (and (stringp val1) (= (length val1) 0))
-                (setq val1 nil))
-            (unless (or (consp char)
-                        (integerp decoder))
-              (setq val2
-                    (cond ((functionp decoder)
-                           (funcall decoder char (aref table char) table))
-                          (t            ; must be nil
-                           (aref table char))))
-              (if val1
-                  (cond ((eq generator 'unidata-gen-table-symbol)
-                         (setq val1 (intern val1)))
-                        ((eq generator 'unidata-gen-table-integer)
-                         (setq val1 (string-to-number val1)))
-                        ((eq generator 'unidata-gen-table-character)
-                         (setq val1 (string-to-number val1 16)))
-                        ((eq generator 'unidata-gen-table-decomposition)
-                         (setq val1 (unidata-split-decomposition val1))))
-                (cond ((eq prop 'decomposition)
-                       (setq val1 (list char)))
-                      ((eq prop 'bracket-type)
-                       (setq val1 'n))))
-              (when (>= char check)
-                (message "%S %04X" prop check)
-                (setq check (+ check #x400)))
-              (or (equal val1 val2)
-                  ;; <control> characters get a 'name' property of nil
-                  (and (eq prop 'name) (string= val1 "<control>") (null val2))
-                  (insert (format "> %04X %S\n< %04X %S\n"
-                                  char val1 char val2)))
-              (sit-for 0))))))))
+             (check #x400)
+             table decoder alist)
+        ;; We compare values in unidata.txt with the ones returned by various
+        ;; generator functions.  However, SpecialCasing.txt is read directly by
+        ;; unidata-gen-table-special-casing--do-load and there is no other file
+        ;; to compare those values with.  This is why we’re skipping the check
+        ;; for special casing properties.
+        (unless (eq generator 'unidata-gen-table-special-casing)
+          (setq table (progn
+                        (message "Generating %S table..." prop)
+                        (funcall generator prop index default-value val-list))
+                decoder (char-table-extra-slot table 1))
+          (unless (integerp decoder)
+            (setq alist (and (functionp index) (funcall index)))
+            (dolist (e unidata-list)
+              (let ((char (car e)) val1 val2)
+                (unless (consp char)
+                  (setq val1 (if alist
+                                 (nth 1 (assoc char alist))
+                               (nth index e)))
+                  (and (stringp val1)
+                       (= (length val1) 0)
+                       (setq val1 nil))
+                  (if val1
+                      (cond ((eq generator 'unidata-gen-table-symbol)
+                             (setq val1 (intern val1)))
+                            ((eq generator 'unidata-gen-table-integer)
+                             (setq val1 (string-to-number val1)))
+                            ((eq generator 'unidata-gen-table-character)
+                             (setq val1 (string-to-number val1 16)))
+                            ((eq generator 'unidata-gen-table-decomposition)
+                             (setq val1 (unidata-split-decomposition val1))))
+                    (cond ((eq prop 'decomposition)
+                           (setq val1 (list char)))
+                          ((eq prop 'bracket-type)
+                           (setq val1 'n))))
+                  (setq val2 (aref table char))
+                  (when decoder
+                    (setq val2 (funcall decoder char val2 table)))
+                  (when (>= char check)
+                    (message "%S %04X" prop check)
+                    (setq check (+ check #x400)))
+                  (or (equal val1 val2)
+                      ;; <control> characters get a 'name' property of nil
+                      (and (eq prop 'name)
+                           (string= val1 "<control>")
+                           (null val2))
+                      (insert (format "> %04X %S\n< %04X %S\n"
+                                      char val1 char val2)))
+                  (sit-for 0))))))))))
 
 ;; The entry functions.  They generate files described in the header
 ;; comment of this file.
diff --git a/configure.ac b/configure.ac
index 65c5f9268ad..ef61107b025 100644
--- a/configure.ac
+++ b/configure.ac
@@ -4240,7 +4240,7 @@ AC_CHECK_HEADERS(valgrind/valgrind.h)
 
 AC_CHECK_MEMBERS([struct unipair.unicode], [], [], [[#include <linux/kd.h>]])
 
-AC_CHECK_FUNCS_ONCE([getc_unlocked sbrk])
+AC_CHECK_FUNCS_ONCE([sbrk])
 
 ok_so_far=yes
 AC_CHECK_FUNC(socket, , ok_so_far=no)
diff --git a/lib-src/ebrowse.c b/lib-src/ebrowse.c
index 51d181997b1..e77b7c94cca 100644
--- a/lib-src/ebrowse.c
+++ b/lib-src/ebrowse.c
@@ -20,21 +20,21 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include <config.h>
 #include <stddef.h>
-#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <ctype.h>
 #include <assert.h>
 #include <getopt.h>
 
+#include <flexmember.h>
+#include <min-max.h>
+#include <unlocked-io.h>
+
 /* The SunOS compiler doesn't have SEEK_END.  */
 #ifndef SEEK_END
 #define SEEK_END 2
 #endif
 
-#include <flexmember.h>
-#include <min-max.h>
-
 /* Files are read in chunks of this number of bytes.  */
 
 enum { READ_CHUNK_SIZE = 100 * 1024 };
diff --git a/lib-src/emacsclient.c b/lib-src/emacsclient.c
index 8828b7652de..f1d4e8976da 100644
--- a/lib-src/emacsclient.c
+++ b/lib-src/emacsclient.c
@@ -73,7 +73,6 @@ char *w32_getenv (const char *);
 
 #include <stdarg.h>
 #include <ctype.h>
-#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <getopt.h>
@@ -84,6 +83,8 @@ char *w32_getenv (const char *);
 #include <signal.h>
 #include <errno.h>
 
+#include <unlocked-io.h>
+
 #ifndef VERSION
 #define VERSION "unspecified"
 #endif
diff --git a/lib-src/etags.c b/lib-src/etags.c
index 6f280d8ab40..e5ff7bd10fc 100644
--- a/lib-src/etags.c
+++ b/lib-src/etags.c
@@ -123,6 +123,7 @@ char pot_etags_version[] = "@(#) pot revision number is 17.38.1.4";
 #include <errno.h>
 #include <fcntl.h>
 #include <binary-io.h>
+#include <unlocked-io.h>
 #include <c-ctype.h>
 #include <c-strcase.h>
 
diff --git a/lib-src/hexl.c b/lib-src/hexl.c
index 319ce8bc890..d949af08902 100644
--- a/lib-src/hexl.c
+++ b/lib-src/hexl.c
@@ -22,11 +22,11 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <config.h>
 
 #include <inttypes.h>
-#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
 #include <binary-io.h>
+#include <unlocked-io.h>
 
 static char *progname;
 
diff --git a/lib-src/make-docfile.c b/lib-src/make-docfile.c
index 9470bd635f5..6b2cc110403 100644
--- a/lib-src/make-docfile.c
+++ b/lib-src/make-docfile.c
@@ -39,10 +39,14 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <stdarg.h>
 #include <stddef.h>
 #include <stdint.h>
-#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
+#include <binary-io.h>
+#include <intprops.h>
+#include <min-max.h>
+#include <unlocked-io.h>
+
 #ifdef WINDOWSNT
 /* Defined to be sys_fopen in ms-w32.h, but only #ifdef emacs, so this
    is really just insurance.  */
@@ -50,10 +54,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <direct.h>
 #endif /* WINDOWSNT */
 
-#include <binary-io.h>
-#include <intprops.h>
-#include <min-max.h>
-
 #ifdef DOS_NT
 /* Defined to be sys_chdir in ms-w32.h, but only #ifdef emacs, so this
    is really just insurance.
diff --git a/lib-src/movemail.c b/lib-src/movemail.c
index cd12c48ed36..e5ca0b16611 100644
--- a/lib-src/movemail.c
+++ b/lib-src/movemail.c
@@ -59,7 +59,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/file.h>
-#include <stdio.h>
 #include <stdlib.h>
 #include <errno.h>
 #include <time.h>
@@ -69,6 +68,9 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <fcntl.h>
 #include <signal.h>
 #include <string.h>
+
+#include <unlocked-io.h>
+
 #include "syswait.h"
 #ifdef MAIL_USE_POP
 #include "pop.h"
diff --git a/lib-src/profile.c b/lib-src/profile.c
index 253f00e2d80..f4ab45c1718 100644
--- a/lib-src/profile.c
+++ b/lib-src/profile.c
@@ -34,11 +34,11 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <config.h>
 
 #include <inttypes.h>
-#include <stdio.h>
 #include <stdlib.h>
 
 #include <intprops.h>
 #include <systime.h>
+#include <unlocked-io.h>
 
 static struct timespec TV1;
 static int watch_not_started = 1; /* flag */
diff --git a/lib-src/update-game-score.c b/lib-src/update-game-score.c
index 5edc8e79569..942aeeb399d 100644
--- a/lib-src/update-game-score.c
+++ b/lib-src/update-game-score.c
@@ -39,7 +39,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <limits.h>
 #include <string.h>
 #include <stdlib.h>
-#include <stdio.h>
 #include <time.h>
 #include <pwd.h>
 #include <ctype.h>
@@ -47,6 +46,8 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <sys/stat.h>
 #include <getopt.h>
 
+#include <unlocked-io.h>
+
 #ifdef WINDOWSNT
 #include "ntlib.h"
 #endif
diff --git a/lib/gnulib.mk.in b/lib/gnulib.mk.in
index 509089e6391..fd0f9e5c780 100644
--- a/lib/gnulib.mk.in
+++ b/lib/gnulib.mk.in
@@ -21,7 +21,7 @@
 # the same distribution terms as the rest of that program.
 #
 # Generated by gnulib-tool.
-# Reproduce by: gnulib-tool --import --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=close --avoid=dup --avoid=fchdir --avoid=fstat --avoid=malloc-posix --avoid=msvc-inval --avoid=msvc-nothrow --avoid=open --avoid=openat-die --avoid=opendir --avoid=raise --avoid=save-cwd --avoid=select --avoid=setenv --avoid=sigprocmask --avoid=stat --avoid=stdarg --avoid=stdbool --avoid=threadlib --avoid=tzset --avoid=unsetenv --avoid=utime --avoid=utime-h --gnu-make --makefile-name=gnulib.mk.in --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt binary-io byteswap c-ctype c-strcase careadlinkat close-stream count-leading-zeros count-one-bits count-trailing-zeros crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 diffseq dtoastr dtotimespec dup2 environ execinfo faccessat fcntl fcntl-h fdatasync fdopendir filemode filevercmp flexmember fstatat fsync getloadavg getopt-gnu gettime gettimeofday gitlog-to-changelog ignore-value intprops largefile lstat manywarnings memrchr minmax mkostemp mktime pipe2 pselect pthread_sigmask putenv qcopy-acl readlink readlinkat sig2str socklen stat-time std-gnu11 stdalign stddef stdio stpcpy strftime strtoimax symlink sys_stat sys_time time time_r time_rz timegm timer-time timespec-add timespec-sub update-copyright utimens vla warnings
+# Reproduce by: gnulib-tool --import --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=close --avoid=dup --avoid=fchdir --avoid=fstat --avoid=malloc-posix --avoid=msvc-inval --avoid=msvc-nothrow --avoid=open --avoid=openat-die --avoid=opendir --avoid=raise --avoid=save-cwd --avoid=select --avoid=setenv --avoid=sigprocmask --avoid=stat --avoid=stdarg --avoid=stdbool --avoid=threadlib --avoid=tzset --avoid=unsetenv --avoid=utime --avoid=utime-h --gnu-make --makefile-name=gnulib.mk.in --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt binary-io byteswap c-ctype c-strcase careadlinkat close-stream count-leading-zeros count-one-bits count-trailing-zeros crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 diffseq dtoastr dtotimespec dup2 environ execinfo faccessat fcntl fcntl-h fdatasync fdopendir filemode filevercmp flexmember fstatat fsync getloadavg getopt-gnu gettime gettimeofday gitlog-to-changelog ignore-value intprops largefile lstat manywarnings memrchr minmax mkostemp mktime pipe2 pselect pthread_sigmask putenv qcopy-acl readlink readlinkat sig2str socklen stat-time std-gnu11 stdalign stddef stdio stpcpy strftime strtoimax symlink sys_stat sys_time time time_r time_rz timegm timer-time timespec-add timespec-sub unlocked-io update-copyright utimens vla warnings
 
 
 MOSTLYCLEANFILES += core *.stackdump
@@ -2996,6 +2996,15 @@ EXTRA_DIST += unistd.in.h
 endif
 ## end   gnulib module unistd
 
+## begin gnulib module unlocked-io
+ifeq (,$(OMIT_GNULIB_MODULE_unlocked-io))
+
+
+EXTRA_DIST += unlocked-io.h
+
+endif
+## end   gnulib module unlocked-io
+
 ## begin gnulib module update-copyright
 ifeq (,$(OMIT_GNULIB_MODULE_update-copyright))
 
diff --git a/lib/unlocked-io.h b/lib/unlocked-io.h
new file mode 100644
index 00000000000..aaf60a0fb4e
--- /dev/null
+++ b/lib/unlocked-io.h
@@ -0,0 +1,136 @@
+/* Prefer faster, non-thread-safe stdio functions if available.
+
+   Copyright (C) 2001-2004, 2009-2017 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* Written by Jim Meyering.  */
+
+#ifndef UNLOCKED_IO_H
+# define UNLOCKED_IO_H 1
+
+/* These are wrappers for functions/macros from the GNU C library, and
+   from other C libraries supporting POSIX's optional thread-safe functions.
+
+   The standard I/O functions are thread-safe.  These *_unlocked ones are
+   more efficient but not thread-safe.  That they're not thread-safe is
+   fine since all of the applications in this package are single threaded.
+
+   Also, some code that is shared with the GNU C library may invoke
+   the *_unlocked functions directly.  On hosts that lack those
+   functions, invoke the non-thread-safe versions instead.  */
+
+# include <stdio.h>
+
+# if HAVE_DECL_CLEARERR_UNLOCKED
+#  undef clearerr
+#  define clearerr(x) clearerr_unlocked (x)
+# else
+#  define clearerr_unlocked(x) clearerr (x)
+# endif
+
+# if HAVE_DECL_FEOF_UNLOCKED
+#  undef feof
+#  define feof(x) feof_unlocked (x)
+# else
+#  define feof_unlocked(x) feof (x)
+# endif
+
+# if HAVE_DECL_FERROR_UNLOCKED
+#  undef ferror
+#  define ferror(x) ferror_unlocked (x)
+# else
+#  define ferror_unlocked(x) ferror (x)
+# endif
+
+# if HAVE_DECL_FFLUSH_UNLOCKED
+#  undef fflush
+#  define fflush(x) fflush_unlocked (x)
+# else
+#  define fflush_unlocked(x) fflush (x)
+# endif
+
+# if HAVE_DECL_FGETS_UNLOCKED
+#  undef fgets
+#  define fgets(x,y,z) fgets_unlocked (x,y,z)
+# else
+#  define fgets_unlocked(x,y,z) fgets (x,y,z)
+# endif
+
+# if HAVE_DECL_FPUTC_UNLOCKED
+#  undef fputc
+#  define fputc(x,y) fputc_unlocked (x,y)
+# else
+#  define fputc_unlocked(x,y) fputc (x,y)
+# endif
+
+# if HAVE_DECL_FPUTS_UNLOCKED
+#  undef fputs
+#  define fputs(x,y) fputs_unlocked (x,y)
+# else
+#  define fputs_unlocked(x,y) fputs (x,y)
+# endif
+
+# if HAVE_DECL_FREAD_UNLOCKED
+#  undef fread
+#  define fread(w,x,y,z) fread_unlocked (w,x,y,z)
+# else
+#  define fread_unlocked(w,x,y,z) fread (w,x,y,z)
+# endif
+
+# if HAVE_DECL_FWRITE_UNLOCKED
+#  undef fwrite
+#  define fwrite(w,x,y,z) fwrite_unlocked (w,x,y,z)
+# else
+#  define fwrite_unlocked(w,x,y,z) fwrite (w,x,y,z)
+# endif
+
+# if HAVE_DECL_GETC_UNLOCKED
+#  undef getc
+#  define getc(x) getc_unlocked (x)
+# else
+#  define getc_unlocked(x) getc (x)
+# endif
+
+# if HAVE_DECL_GETCHAR_UNLOCKED
+#  undef getchar
+#  define getchar() getchar_unlocked ()
+# else
+#  define getchar_unlocked() getchar ()
+# endif
+
+# if HAVE_DECL_PUTC_UNLOCKED
+#  undef putc
+#  define putc(x,y) putc_unlocked (x,y)
+# else
+#  define putc_unlocked(x,y) putc (x,y)
+# endif
+
+# if HAVE_DECL_PUTCHAR_UNLOCKED
+#  undef putchar
+#  define putchar(x) putchar_unlocked (x)
+# else
+#  define putchar_unlocked(x) putchar (x)
+# endif
+
+# undef flockfile
+# define flockfile(x) ((void) 0)
+
+# undef ftrylockfile
+# define ftrylockfile(x) 0
+
+# undef funlockfile
+# define funlockfile(x) ((void) 0)
+
+#endif /* UNLOCKED_IO_H */
diff --git a/lisp/descr-text.el b/lisp/descr-text.el
index 6a6a8ea4479..6f36bbed680 100644
--- a/lisp/descr-text.el
+++ b/lisp/descr-text.el
@@ -413,12 +413,11 @@ relevant to POS."
            (multibyte-p enable-multibyte-characters)
            (overlays (mapcar (lambda (o) (overlay-properties o))
                              (overlays-at pos)))
-           (char-description (if (not multibyte-p)
+           (char-description (if (< char 128)
                                  (single-key-description char)
-                               (if (< char 128)
-                                   (single-key-description char)
-                                 (string-to-multibyte
-                                  (char-to-string char)))))
+                               (string (if (not multibyte-p)
+                                           (decode-char 'eight-bit char)
+                                         char))))
            (text-props-desc
             (let ((tmp-buf (generate-new-buffer " *text-props*")))
               (unwind-protect
@@ -635,7 +634,9 @@ relevant to POS."
               ("buffer code"
                ,(if multibyte-p
                     (encoded-string-description
-                     (string-as-unibyte (char-to-string char)) nil)
+                     (encode-coding-string (char-to-string char)
+                                           'emacs-internal)
+                     nil)
                   (format "#x%02X" char)))
               ("file code"
                ,@(if multibyte-p
@@ -704,7 +705,6 @@ relevant to POS."
                        (called-interactively-p 'interactive))
       (with-help-window (help-buffer)
         (with-current-buffer standard-output
-          (set-buffer-multibyte multibyte-p)
           (let ((formatter (format "%%%ds:" max-width)))
             (dolist (elt item-list)
               (when (cadr elt)
diff --git a/lisp/net/shr.el b/lisp/net/shr.el
index 2a6b3960c46..45ef379af54 100644
--- a/lisp/net/shr.el
+++ b/lisp/net/shr.el
@@ -512,6 +512,7 @@ size, and full-buffer size."
                                        (* (frame-char-width) 2)
                                      0))))
         (shr-insert text)
+        (shr-fill-lines (point-min) (point-max))
         (buffer-string)))))
 
 (define-inline shr-char-breakable-p (char)
diff --git a/m4/gnulib-comp.m4 b/m4/gnulib-comp.m4
index 1ac58e871cc..107645df4fd 100644
--- a/m4/gnulib-comp.m4
+++ b/m4/gnulib-comp.m4
@@ -158,6 +158,7 @@ AC_DEFUN([gl_EARLY],
   # Code from module timespec-sub:
   # Code from module u64:
   # Code from module unistd:
+  # Code from module unlocked-io:
   # Code from module update-copyright:
   # Code from module utimens:
   # Code from module vararrays:
@@ -399,6 +400,7 @@ AC_DEFUN([gl_INIT],
   gl_TIMER_TIME
   gl_TIMESPEC
   gl_UNISTD_H
+  gl_FUNC_GLIBC_UNLOCKED_IO
   gl_UTIMENS
   AC_C_VARARRAYS
   gl_gnulib_enabled_260941c0e5dc67ec9e87d1fb321c300b=false
@@ -940,6 +942,7 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/u64.h
   lib/unistd.c
   lib/unistd.in.h
+  lib/unlocked-io.h
   lib/utimens.c
   lib/utimens.h
   lib/verify.h
@@ -1044,6 +1047,7 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/timespec.m4
   m4/tm_gmtoff.m4
   m4/unistd_h.m4
+  m4/unlocked-io.m4
   m4/utimens.m4
   m4/utimes.m4
   m4/vararrays.m4
diff --git a/m4/unlocked-io.m4 b/m4/unlocked-io.m4
new file mode 100644
index 00000000000..448ccac2f0e
--- /dev/null
+++ b/m4/unlocked-io.m4
@@ -0,0 +1,41 @@
+# unlocked-io.m4 serial 15
+
+# Copyright (C) 1998-2006, 2009-2017 Free Software Foundation, Inc.
+#
+# This file is free software; the Free Software Foundation
+# gives unlimited permission to copy and/or distribute it,
+# with or without modifications, as long as this notice is preserved.
+
+dnl From Jim Meyering.
+dnl
+dnl See if the glibc *_unlocked I/O macros or functions are available.
+dnl Use only those *_unlocked macros or functions that are declared
+dnl (because some of them were declared in Solaris 2.5.1 but were removed
+dnl in Solaris 2.6, whereas we want binaries built on Solaris 2.5.1 to run
+dnl on Solaris 2.6).
+
+AC_DEFUN([gl_FUNC_GLIBC_UNLOCKED_IO],
+[
+  AC_DEFINE([USE_UNLOCKED_IO], [1],
+    [Define to 1 if you want getc etc. to use unlocked I/O if available.
+     Unlocked I/O can improve performance in unithreaded apps,
+     but it is not safe for multithreaded apps.])
+
+  dnl Persuade glibc and Solaris <stdio.h> to declare
+  dnl fgets_unlocked(), fputs_unlocked() etc.
+  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+
+  AC_CHECK_DECLS_ONCE([clearerr_unlocked])
+  AC_CHECK_DECLS_ONCE([feof_unlocked])
+  AC_CHECK_DECLS_ONCE([ferror_unlocked])
+  AC_CHECK_DECLS_ONCE([fflush_unlocked])
+  AC_CHECK_DECLS_ONCE([fgets_unlocked])
+  AC_CHECK_DECLS_ONCE([fputc_unlocked])
+  AC_CHECK_DECLS_ONCE([fputs_unlocked])
+  AC_CHECK_DECLS_ONCE([fread_unlocked])
+  AC_CHECK_DECLS_ONCE([fwrite_unlocked])
+  AC_CHECK_DECLS_ONCE([getc_unlocked])
+  AC_CHECK_DECLS_ONCE([getchar_unlocked])
+  AC_CHECK_DECLS_ONCE([putc_unlocked])
+  AC_CHECK_DECLS_ONCE([putchar_unlocked])
+])
diff --git a/src/charset.c b/src/charset.c
index 9d15375dd79..d0840f7d2a9 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -29,7 +29,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <config.h>
 
 #include <errno.h>
-#include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <limits.h>
@@ -40,6 +39,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include "charset.h"
 #include "coding.h"
 #include "buffer.h"
+#include "sysstdio.h"
 
 /*** GENERAL NOTES on CODED CHARACTER SETS (CHARSETS) ***
 
@@ -198,10 +198,6 @@ static struct
 
 #define GET_TEMP_CHARSET_WORK_DECODER(CODE)     \
   (temp_charset_work->table.decoder[(CODE)])
-
-#ifndef HAVE_GETC_UNLOCKED
-#define getc_unlocked getc
-#endif
 
 
 /* Set to 1 to warn that a charset map is loaded and thus a buffer
diff --git a/src/cm.c b/src/cm.c
index efa50b0f58d..9a90f37445c 100644
--- a/src/cm.c
+++ b/src/cm.c
@@ -19,10 +19,10 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 
 #include <config.h>
-#include <stdio.h>
 
 #include "lisp.h"
 #include "cm.h"
+#include "sysstdio.h"
 #include "termchar.h"
 #include "tparam.h"
 
@@ -45,8 +45,8 @@ int
 cmputc (int c)
 {
   if (current_tty->termscript)
-    putc (c & 0177, current_tty->termscript);
-  putc (c & 0177, current_tty->output);
+    putc_unlocked (c & 0177, current_tty->termscript);
+  putc_unlocked (c & 0177, current_tty->output);
   return c;
 }
 
@@ -117,11 +117,11 @@ cmcheckmagic (struct tty_display_info *tty)
       if (!MagicWrap (tty) || curY (tty) >= FrameRows (tty) - 1)
         emacs_abort ();
       if (tty->termscript)
-        putc ('\r', tty->termscript);
-      putc ('\r', tty->output);
+        putc_unlocked ('\r', tty->termscript);
+      putc_unlocked ('\r', tty->output);
       if (tty->termscript)
-        putc ('\n', tty->termscript);
-      putc ('\n', tty->output);
+        putc_unlocked ('\n', tty->termscript);
+      putc_unlocked ('\n', tty->output);
       curX (tty) = 0;
       curY (tty)++;
     }
diff --git a/src/dispnew.c b/src/dispnew.c
index 27c69bde831..925e44d9804 100644
--- a/src/dispnew.c
+++ b/src/dispnew.c
@@ -3126,9 +3126,9 @@ update_frame (struct frame *f, bool force_p, bool inhibit_hairy_id_p)
       if (FRAME_TERMCAP_P (f) || FRAME_MSDOS_P (f))
         {
           if (FRAME_TTY (f)->termscript)
-            fflush (FRAME_TTY (f)->termscript);
+            fflush_unlocked (FRAME_TTY (f)->termscript);
           if (FRAME_TERMCAP_P (f))
-            fflush (FRAME_TTY (f)->output);
+            fflush_unlocked (FRAME_TTY (f)->output);
         }
 
       /* Check window matrices for lost pointers.  */
@@ -3181,8 +3181,8 @@ update_frame_with_menu (struct frame *f, int row, int col)
   update_end (f);
 
   if (FRAME_TTY (f)->termscript)
-    fflush (FRAME_TTY (f)->termscript);
-  fflush (FRAME_TTY (f)->output);
+    fflush_unlocked (FRAME_TTY (f)->termscript);
+  fflush_unlocked (FRAME_TTY (f)->output);
   /* Check window matrices for lost pointers.  */
 #if GLYPH_DEBUG
 #if 0
@@ -4531,7 +4531,7 @@ update_frame_1 (struct frame *f, bool force_p, bool inhibit_id_p,
                   ptrdiff_t outq = __fpending (display_output);
                   if (outq > 900
                       || (outq > 20 && ((i - 1) % preempt_count == 0)))
-                    fflush (display_output);
+                    fflush_unlocked (display_output);
                 }
             }
 
@@ -5615,13 +5615,13 @@ when TERMINAL is nil.  */)
 
       if (tty->termscript)
         {
-          fwrite (SDATA (string), 1, SBYTES (string), tty->termscript);
-          fflush (tty->termscript);
+          fwrite_unlocked (SDATA (string), 1, SBYTES (string), tty->termscript);
+          fflush_unlocked (tty->termscript);
         }
       out = tty->output;
     }
-  fwrite (SDATA (string), 1, SBYTES (string), out);
-  fflush (out);
+  fwrite_unlocked (SDATA (string), 1, SBYTES (string), out);
+  fflush_unlocked (out);
   unblock_input ();
   return Qnil;
 }
@@ -5636,7 +5636,7 @@ terminate any keyboard macro currently executing.  */)
   if (!NILP (arg))
     {
       if (noninteractive)
-        putchar (07);
+        putchar_unlocked (07);
       else
         ring_bell (XFRAME (selected_frame));
     }
@@ -5650,7 +5650,7 @@ void
 bitch_at_user (void)
 {
   if (noninteractive)
-    putchar (07);
+    putchar_unlocked (07);
   else if (!INTERACTIVE)  /* Stop executing a keyboard macro.  */
     {
       const char *msg
diff --git a/src/emacs.c b/src/emacs.c
index da8df1bf1c7..0fec7167588 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -23,7 +23,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include <errno.h>
 #include <fcntl.h>
-#include <stdio.h>
 #include <stdlib.h>
 
 #include <sys/file.h>
@@ -33,6 +32,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #define MAIN_PROGRAM
 #include "lisp.h"
+#include "sysstdio.h"
 
 #ifdef WINDOWSNT
 #include <fcntl.h>
@@ -885,7 +885,7 @@ main (int argc, char **argv)
     }
 #endif /* HAVE_SETRLIMIT and RLIMIT_STACK and not CYGWIN */
 
-  clearerr (stdin);
+  clearerr_unlocked (stdin);
 
   emacs_backtrace (-1);
 
@@ -983,7 +983,7 @@ main (int argc, char **argv)
       int i;
       printf ("Usage: %s [OPTION-OR-FILENAME]...\n", argv[0]);
       for (i = 0; i < ARRAYELTS (usage_message); i++)
-        fputs (usage_message[i], stdout);
+        fputs_unlocked (usage_message[i], stdout);
       exit (0);
     }
 
@@ -2197,7 +2197,7 @@ You must run Emacs in batch mode in order to dump it.  */)
   }
 #endif
 
-  fflush (stdout);
+  fflush_unlocked (stdout);
   /* Tell malloc where start of impure now is.  */
   /* Also arrange for warnings when nearly out of space.  */
 #if !defined SYSTEM_MALLOC && !defined HYBRID_MALLOC
diff --git a/src/fileio.c b/src/fileio.c
index cb070029a9b..a57d50b24e0 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -5643,14 +5643,12 @@ A non-nil CURRENT-ONLY argument means save only current buffer.  */)
           {
             block_input ();
             if (!NILP (BVAR (b, filename)))
-              {
-                fwrite (SDATA (BVAR (b, filename)), 1,
-                        SBYTES (BVAR (b, filename)), stream);
-              }
-            putc ('\n', stream);
-            fwrite (SDATA (BVAR (b, auto_save_file_name)), 1,
-                    SBYTES (BVAR (b, auto_save_file_name)), stream);
-            putc ('\n', stream);
+              fwrite_unlocked (SDATA (BVAR (b, filename)), 1,
+                               SBYTES (BVAR (b, filename)), stream);
+            putc_unlocked ('\n', stream);
+            fwrite_unlocked (SDATA (BVAR (b, auto_save_file_name)), 1,
+                             SBYTES (BVAR (b, auto_save_file_name)), stream);
+            putc_unlocked ('\n', stream);
             unblock_input ();
           }
 
@@ -5841,7 +5839,7 @@ effect except for flushing STREAM's data.  */)
 
   binmode = NILP (mode) ? O_TEXT : O_BINARY;
   if (fp != stdin)
-    fflush (fp);
+    fflush_unlocked (fp);
 
   return (set_binary_mode (fileno (fp), binmode) == O_BINARY) ? Qt : Qnil;
 }
diff --git a/src/image.c b/src/image.c
index aedec7954ee..07c4769e9e3 100644
--- a/src/image.c
+++ b/src/image.c
@@ -20,7 +20,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <config.h>
 
 #include <fcntl.h>
-#include <stdio.h>
 #include <unistd.h>
 
 /* Include this before including <setjmp.h> to work around bugs with
@@ -41,6 +40,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include "buffer.h"
 #include "dispextern.h"
 #include "blockinput.h"
+#include "sysstdio.h"
 #include "systime.h"
 #include <epaths.h>
 #include "coding.h"
@@ -2361,7 +2361,7 @@ slurp_file (int fd, ptrdiff_t *size)
              This can happen if the file grows as we read it.  */
           ptrdiff_t buflen = st.st_size;
           buf = xmalloc (buflen + 1);
-          if (fread (buf, 1, buflen + 1, fp) == buflen)
+          if (fread_unlocked (buf, 1, buflen + 1, fp) == buflen)
             *size = buflen;
           else
             {
@@ -5890,7 +5890,7 @@ png_read_from_file (png_structp png_ptr, png_bytep data, png_size_t length)
 {
   FILE *fp = png_get_io_ptr (png_ptr);
 
-  if (fread (data, 1, length, fp) < length)
+  if (fread_unlocked (data, 1, length, fp) < length)
     png_error (png_ptr, "Read error");
 }
 
@@ -5959,7 +5959,7 @@ png_load_body (struct frame *f, struct image *img, struct png_load_context *c)
         }
 
       /* Check PNG signature.  */
-      if (fread (sig, 1, sizeof sig, fp) != sizeof sig
+      if (fread_unlocked (sig, 1, sizeof sig, fp) != sizeof sig
           || png_sig_cmp (sig, 0, sizeof sig))
         {
           fclose (fp);
@@ -6598,7 +6598,8 @@ our_stdio_fill_input_buffer (j_decompress_ptr cinfo)
     {
       ptrdiff_t bytes;
 
-      bytes = fread (src->buffer, 1, JPEG_STDIO_BUFFER_SIZE, src->file);
+      bytes = fread_unlocked (src->buffer, 1, JPEG_STDIO_BUFFER_SIZE,
+                              src->file);
       if (bytes > 0)
         src->mgr.bytes_in_buffer = bytes;
       else
diff --git a/src/keyboard.c b/src/keyboard.c
index 55486c6d9ab..3442b18409a 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -39,6 +39,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include "intervals.h"
 #include "keymap.h"
 #include "blockinput.h"
+#include "sysstdio.h"
 #include "systime.h"
 #include "atimer.h"
 #include "process.h"
@@ -3290,7 +3291,7 @@ record_char (Lisp_Object c)
       if (INTEGERP (c))
         {
           if (XUINT (c) < 0x100)
-            putc (XUINT (c), dribble);
+            putc_unlocked (XUINT (c), dribble);
           else
             fprintf (dribble, " 0x%"pI"x", XUINT (c));
         }
@@ -3303,15 +3304,15 @@ record_char (Lisp_Object c)
 
           if (SYMBOLP (dribblee))
             {
-              putc ('<', dribble);
-              fwrite (SDATA (SYMBOL_NAME (dribblee)), sizeof (char),
-                      SBYTES (SYMBOL_NAME (dribblee)),
-                      dribble);
-              putc ('>', dribble);
+              putc_unlocked ('<', dribble);
+              fwrite_unlocked (SDATA (SYMBOL_NAME (dribblee)), sizeof (char),
+                               SBYTES (SYMBOL_NAME (dribblee)),
+                               dribble);
+              putc_unlocked ('>', dribble);
             }
         }
 
-      fflush (dribble);
+      fflush_unlocked (dribble);
       unblock_input ();
     }
 }
@@ -3769,7 +3770,7 @@ kbd_buffer_get_event (KBOARD **kbp,
          detaching from the terminal.  */
       || (IS_DAEMON && DAEMON_RUNNING))
     {
-      int c = getchar ();
+      int c = getchar_unlocked ();
       XSETINT (obj, c);
       *kbp = current_kboard;
       return obj;
@@ -10377,7 +10378,7 @@ handle_interrupt (bool in_signal_handler)
           sigemptyset (&blocked);
           sigaddset (&blocked, SIGINT);
           pthread_sigmask (SIG_BLOCK, &blocked, 0);
-          fflush (stdout);
+          fflush_unlocked (stdout);
         }
 
       reset_all_sys_modes ();
diff --git a/src/lread.c b/src/lread.c
index b01cbd5c072..182f96223a5 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -72,10 +72,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #define file_tell ftell
 #endif
 
-#ifndef HAVE_GETC_UNLOCKED
-#define getc_unlocked getc
-#endif
-
 /* The objects or placeholders read with the #n=object form.
 
    A hash table maps a number to either a placeholder (while the
@@ -474,16 +470,15 @@ readbyte_from_file (int c, Lisp_Object readcharfun)
     }
 
   block_input ();
-  c = getc_unlocked (instream);
 
   /* Interrupted reads have been observed while reading over the network.  */
-  while (c == EOF && ferror (instream) && errno == EINTR)
+  while ((c = getc_unlocked (instream)) == EOF && errno == EINTR
+         && ferror_unlocked (instream))
     {
       unblock_input ();
       maybe_quit ();
       block_input ();
-      clearerr (instream);
-      c = getc_unlocked (instream);
+      clearerr_unlocked (instream);
     }
 
   unblock_input ();
@@ -1942,13 +1937,13 @@ readevalloop (Lisp_Object readcharfun,
         read_objects_map
           = make_hash_table (hashtest_eq, DEFAULT_HASH_SIZE,
                              DEFAULT_REHASH_SIZE, DEFAULT_REHASH_THRESHOLD,
-                             Qnil, Qnil);
+                             Qnil, false);
       if (! HASH_TABLE_P (read_objects_completed)
           || XHASH_TABLE (read_objects_completed)->count)
         read_objects_completed
           = make_hash_table (hashtest_eq, DEFAULT_HASH_SIZE,
                              DEFAULT_REHASH_SIZE, DEFAULT_REHASH_THRESHOLD,
-                             Qnil, Qnil);
+                             Qnil, false);
       if (!NILP (Vpurify_flag) && c == '(')
         {
           val = read_list (0, readcharfun);
@@ -2159,12 +2154,12 @@ read_internal_start (Lisp_Object stream, Lisp_Object start, Lisp_Object end)
       || XHASH_TABLE (read_objects_map)->count)
     read_objects_map
       = make_hash_table (hashtest_eq, DEFAULT_HASH_SIZE, DEFAULT_REHASH_SIZE,
-                         DEFAULT_REHASH_THRESHOLD, Qnil, Qnil);
+                         DEFAULT_REHASH_THRESHOLD, Qnil, false);
   if (! HASH_TABLE_P (read_objects_completed)
       || XHASH_TABLE (read_objects_completed)->count)
     read_objects_completed
       = make_hash_table (hashtest_eq, DEFAULT_HASH_SIZE, DEFAULT_REHASH_SIZE,
-                         DEFAULT_REHASH_THRESHOLD, Qnil, Qnil);
+                         DEFAULT_REHASH_THRESHOLD, Qnil, false);
   if (EQ (Vread_with_symbol_positions, Qt)
       || EQ (Vread_with_symbol_positions, stream))
     Vread_symbol_positions_list = Qnil;
diff --git a/src/minibuf.c b/src/minibuf.c
index 1bbe276776e..835992fa79d 100644
--- a/src/minibuf.c
+++ b/src/minibuf.c
@@ -20,7 +20,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include <config.h>
 #include <errno.h>
-#include <stdio.h>
 
 #include <binary-io.h>
 
@@ -31,6 +30,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include "frame.h"
 #include "window.h"
 #include "keymap.h"
+#include "sysstdio.h"
 #include "systty.h"
 
 /* List of buffers for use as minibuffers.
@@ -209,15 +209,15 @@ read_minibuf_noninteractive (Lisp_Object map, Lisp_Object initial,
       suppress_echo_on_tty (STDIN_FILENO);
     }
 
-  fwrite (SDATA (prompt), 1, SBYTES (prompt), stdout);
-  fflush (stdout);
+  fwrite_unlocked (SDATA (prompt), 1, SBYTES (prompt), stdout);
+  fflush_unlocked (stdout);
 
   val = Qnil;
   size = 100;
   len = 0;
   line = xmalloc (size);
 
-  while ((c = getchar ()) != '\n' && c != '\r')
+  while ((c = getchar_unlocked ()) != '\n' && c != '\r')
     {
       if (c == EOF)
         {
diff --git a/src/print.c b/src/print.c
index aaec5b04956..6bf8af9ef93 100644
--- a/src/print.c
+++ b/src/print.c
@@ -228,7 +228,7 @@ printchar_to_stream (unsigned int ch, FILE *stream)
     {
       if (ASCII_CHAR_P (ch))
         {
-          putc (ch, stream);
+          putc_unlocked (ch, stream);
 #ifdef WINDOWSNT
           /* Send the output to a debugger (nothing happens if there
              isn't one).  */
@@ -246,7 +246,7 @@ printchar_to_stream (unsigned int ch, FILE *stream)
           if (encode_p)
             encoded_ch = code_convert_string_norecord (encoded_ch,
                                                        coding_system, true);
-          fwrite (SSDATA (encoded_ch), 1, SBYTES (encoded_ch), stream);
+          fwrite_unlocked (SSDATA (encoded_ch), 1, SBYTES (encoded_ch), stream);
 #ifdef WINDOWSNT
           if (print_output_debug_flag && stream == stderr)
             OutputDebugString (SSDATA (encoded_ch));
@@ -298,7 +298,7 @@ printchar (unsigned int ch, Lisp_Object fun)
           if (DISP_TABLE_P (Vstandard_display_table))
             printchar_to_stream (ch, stdout);
           else
-            fwrite (str, 1, len, stdout);
+            fwrite_unlocked (str, 1, len, stdout);
           noninteractive_need_newline = 1;
         }
       else
@@ -350,7 +350,7 @@ strout (const char *ptr, ptrdiff_t size, ptrdiff_t size_byte,
             }
         }
       else
-        fwrite (ptr, 1, size_byte, stdout);
+        fwrite_unlocked (ptr, 1, size_byte, stdout);
 
       noninteractive_need_newline = 1;
     }
@@ -801,7 +801,7 @@ append to existing target file.  */)
         report_file_error ("Cannot open debugging output stream", file);
     }
 
-  fflush (stderr);
+  fflush_unlocked (stderr);
   if (dup2 (fd, STDERR_FILENO) < 0)
     report_file_error ("dup2", file);
   if (fd != stderr_dup)
diff --git a/src/sysdep.c b/src/sysdep.c
index 70f4a9dd7ea..b52236769e0 100644
--- a/src/sysdep.c
+++ b/src/sysdep.c
@@ -1408,7 +1408,7 @@ reset_sys_modes (struct tty_display_info *tty_out)
 {
   if (noninteractive)
     {
-      fflush (stdout);
+      fflush_unlocked (stdout);
       return;
     }
   if (!tty_out->term_initted)
@@ -1428,17 +1428,14 @@ reset_sys_modes (struct tty_display_info *tty_out)
     }
   else
     {                   /* have to do it the hard way */
-      int i;
       tty_turn_off_insert (tty_out);
 
-      for (i = cursorX (tty_out); i < FrameCols (tty_out) - 1; i++)
-        {
-          fputc (' ', tty_out->output);
-        }
+      for (int i = cursorX (tty_out); i < FrameCols (tty_out) - 1; i++)
+        fputc_unlocked (' ', tty_out->output);
     }
 
   cmgoto (tty_out, FrameRows (tty_out) - 1, 0);
-  fflush (tty_out->output);
+  fflush_unlocked (tty_out->output);
 
   if (tty_out->terminal->reset_terminal_modes_hook)
     tty_out->terminal->reset_terminal_modes_hook (tty_out->terminal);
@@ -3079,7 +3076,7 @@ procfs_ttyname (int rdev)
       char minor[25];   /* 2 32-bit numbers + dash */
       char *endp;
 
-      for (; !feof (fdev) && !ferror (fdev); name[0] = 0)
+      for (; !feof_unlocked (fdev) && !ferror_unlocked (fdev); name[0] = 0)
         {
           if (fscanf (fdev, "%*s %s %u %s %*s\n", name, &major, minor) >= 3
               && major == MAJOR (rdev))
@@ -3129,7 +3126,7 @@ procfs_get_total_memory (void)
             break;
 
           case 0:
-            while ((c = getc (fmem)) != EOF && c != '\n')
+            while ((c = getc_unlocked (fmem)) != EOF && c != '\n')
               continue;
             done = c == EOF;
             break;
diff --git a/src/sysstdio.h b/src/sysstdio.h
index 45ee33f5580..7fbcefcdad9 100644
--- a/src/sysstdio.h
+++ b/src/sysstdio.h
@@ -33,4 +33,45 @@ extern FILE *emacs_fopen (char const *, char const *);
 # define FOPEN_TEXT ""
 #endif
 
+/* These are compatible with unlocked-io.h, if both files are included.  */
+#if !HAVE_DECL_CLEARERR_UNLOCKED
+# define clearerr_unlocked(x) clearerr (x)
+#endif
+#if !HAVE_DECL_FEOF_UNLOCKED
+# define feof_unlocked(x) feof (x)
+#endif
+#if !HAVE_DECL_FERROR_UNLOCKED
+# define ferror_unlocked(x) ferror (x)
+#endif
+#if !HAVE_DECL_FFLUSH_UNLOCKED
+# define fflush_unlocked(x) fflush (x)
+#endif
+#if !HAVE_DECL_FGETS_UNLOCKED
+# define fgets_unlocked(x,y,z) fgets (x,y,z)
+#endif
+#if !HAVE_DECL_FPUTC_UNLOCKED
+# define fputc_unlocked(x,y) fputc (x,y)
+#endif
+#if !HAVE_DECL_FPUTS_UNLOCKED
+# define fputs_unlocked(x,y) fputs (x,y)
+#endif
+#if !HAVE_DECL_FREAD_UNLOCKED
+# define fread_unlocked(w,x,y,z) fread (w,x,y,z)
+#endif
+#if !HAVE_DECL_FWRITE_UNLOCKED
+# define fwrite_unlocked(w,x,y,z) fwrite (w,x,y,z)
+#endif
+#if !HAVE_DECL_GETC_UNLOCKED
+# define getc_unlocked(x) getc (x)
+#endif
+#if !HAVE_DECL_GETCHAR_UNLOCKED
+# define getchar_unlocked() getchar ()
+#endif
+#if !HAVE_DECL_PUTC_UNLOCKED
+# define putc_unlocked(x,y) putc (x,y)
+#endif
+#if !HAVE_DECL_PUTCHAR_UNLOCKED
+# define putchar_unlocked(x) putchar (x)
+#endif
+
 #endif /* EMACS_SYSSTDIO_H */
diff --git a/src/term.c b/src/term.c
index 8770aff8a92..3d7f4ada0b9 100644
--- a/src/term.c
+++ b/src/term.c
@@ -22,7 +22,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include <config.h>
 #include <errno.h>
 #include <fcntl.h>
-#include <stdio.h>
 #include <stdlib.h>
 #include <sys/file.h>
 #include <sys/time.h>
@@ -45,6 +44,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include "keymap.h"
 #include "blockinput.h"
 #include "syssignal.h"
+#include "sysstdio.h"
 #ifdef MSDOS
 #include "msdos.h"
 static int been_here = -1;
@@ -146,7 +146,7 @@ tty_ring_bell (struct frame *f)
       OUTPUT (tty, (tty->TS_visible_bell && visible_bell
                     ? tty->TS_visible_bell
                     : tty->TS_bell));
-      fflush (tty->output);
+      fflush_unlocked (tty->output);
     }
 }
 
@@ -167,9 +167,10 @@ tty_send_additional_strings (struct terminal *terminal, Lisp_Object sym)
       Lisp_Object string = XCAR (extra_codes);
       if (STRINGP (string))
         {
-          fwrite (SDATA (string), 1, SBYTES (string), tty->output);
+          fwrite_unlocked (SDATA (string), 1, SBYTES (string), tty->output);
           if (tty->termscript)
-            fwrite (SDATA (string), 1, SBYTES (string), tty->termscript);
+            fwrite_unlocked (SDATA (string), 1, SBYTES (string),
+                             tty->termscript);
         }
     }
 }
@@ -197,7 +198,7 @@ tty_set_terminal_modes (struct terminal *terminal)
       OUTPUT_IF (tty, tty->TS_keypad_mode);
       losecursor (tty);
       tty_send_additional_strings (terminal, Qtty_mode_set_strings);
-      fflush (tty->output);
+      fflush_unlocked (tty->output);
     }
 }
 
@@ -220,7 +221,7 @@ tty_reset_terminal_modes (struct terminal *terminal)
       /* Output raw CR so kernel can track the cursor hpos.  */
       current_tty = tty;
       cmputc ('\r');
-      fflush (tty->output);
+      fflush_unlocked (tty->output);
     }
 }
 
@@ -235,7 +236,7 @@ tty_update_end (struct frame *f)
     tty_show_cursor (tty);
   tty_turn_off_insert (tty);
   tty_background_highlight (tty);
-  fflush (tty->output);
+  fflush_unlocked (tty->output);
 }
 
 /* The implementation of set_terminal_window for termcap frames. */
@@ -497,8 +498,8 @@ tty_clear_end_of_line (struct frame *f, int first_unused_hpos)
       for (i = curX (tty); i < first_unused_hpos; i++)
         {
           if (tty->termscript)
-            fputc (' ', tty->termscript);
-          fputc (' ', tty->output);
+            fputc_unlocked (' ', tty->termscript);
+          fputc_unlocked (' ', tty->output);
         }
       cmplus (tty, first_unused_hpos - curX (tty));
     }
@@ -771,11 +772,11 @@ tty_write_glyphs (struct frame *f, struct glyph *string, int len)
       if (coding->produced > 0)
         {
           block_input ();
-          fwrite (conversion_buffer, 1, coding->produced, tty->output);
-          if (ferror (tty->output))
-            clearerr (tty->output);
+          fwrite_unlocked (conversion_buffer, 1, coding->produced, tty->output);
+          clearerr_unlocked (tty->output);
           if (tty->termscript)
-            fwrite (conversion_buffer, 1, coding->produced, tty->termscript);
+            fwrite_unlocked (conversion_buffer, 1, coding->produced,
+                             tty->termscript);
           unblock_input ();
         }
       string += n;
@@ -832,11 +833,11 @@ tty_write_glyphs_with_face (register struct frame *f, register struct glyph *str
   if (coding->produced > 0)
     {
       block_input ();
-      fwrite (conversion_buffer, 1, coding->produced, tty->output);
-      if (ferror (tty->output))
-        clearerr (tty->output);
+      fwrite_unlocked (conversion_buffer, 1, coding->produced, tty->output);
+      clearerr_unlocked (tty->output);
       if (tty->termscript)
-        fwrite (conversion_buffer, 1, coding->produced, tty->termscript);
+        fwrite_unlocked (conversion_buffer, 1, coding->produced,
+                         tty->termscript);
       unblock_input ();
     }
 
@@ -918,11 +919,11 @@ tty_insert_glyphs (struct frame *f, struct glyph *start, int len)
       if (coding->produced > 0)
         {
           block_input ();
-          fwrite (conversion_buffer, 1, coding->produced, tty->output);
-          if (ferror (tty->output))
-            clearerr (tty->output);
+          fwrite_unlocked (conversion_buffer, 1, coding->produced, tty->output);
+          clearerr_unlocked (tty->output);
           if (tty->termscript)
-            fwrite (conversion_buffer, 1, coding->produced, tty->termscript);
+            fwrite_unlocked (conversion_buffer, 1, coding->produced,
+                             tty->termscript);
           unblock_input ();
         }
 
@@ -3327,7 +3328,7 @@ tty_menu_activate (tty_menu *menu, int *pane, int *selidx,
          which calls tty_show_cursor.  Re-hide it, so it doesn't show
          through the menus.  */
       tty_hide_cursor (tty);
-      fflush (tty->output);
+      fflush_unlocked (tty->output);
     }
 
   sf->mouse_moved = 0;
@@ -3335,7 +3336,7 @@ tty_menu_activate (tty_menu *menu, int *pane, int *selidx,
   while (statecount--)
     free_saved_screen (state[statecount].screen_behind);
   tty_show_cursor (tty);        /* Turn cursor back on.  */
-  fflush (tty->output);
+  fflush_unlocked (tty->output);
 
 /* Clean up any mouse events that are waiting inside Emacs event queue.
      These events are likely to be generated before the menu was even
diff --git a/src/xfaces.c b/src/xfaces.c
index 4714b7b3cb8..86bb9b0b496 100644
--- a/src/xfaces.c
+++ b/src/xfaces.c
@@ -6232,7 +6232,7 @@ where R,G,B are numbers between 0 and 255 and name is an arbitrary string.  */)
       int red, green, blue;
       int num;
 
-      while (fgets (buf, sizeof (buf), fp) != NULL) {
+      while (fgets_unlocked (buf, sizeof (buf), fp) != NULL) {
         if (sscanf (buf, "%d %d %d %n", &red, &green, &blue, &num) == 3)
           {
 #ifdef HAVE_NTGUI