--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,26 @@
 2011-01-19  Paul Eggert  <eggert@cs.ucla.edu>
 
+	assume <ctype.h>, ..., <time.h> exist
+	For years gnulib has been assuming the existence of the headers
+	<ctime.h>, <errno.h>, <fcntl.h>, <locale.h>, <signal.h>,
+	<stdio.h>, <stdlib.h>, <string.h>, and <time.h>.  Omit checks for
+	them, since they don't appear to be needed.
+	* README (Portability guidelines): Document this.
+	* lib/flock.c: Assume <fcntl.h> exists.
+	* lib/regex_internal.h: Assume <locale.h> exists.
+	* m4/ctype.m4 (gl_CTYPE_H): Assume <ctype.h> exists.
+	* m4/errno_h.m4 (gl_HEADER_ERRNO_H): Assume <errno.h> exists.
+	* m4/fcntl_h.m4 (gl_FCNTL_H): Assume <fcntl.h> exists.
+	* m4/flock.m4 (gl_PREREQ_FLOCK): Likewise.
+	* m4/locale_h.m4 (gl_LOCALE_H): Assume <locale.h> exists.
+	* m4/regex.m4 (gl_REGEX): Likewise.
+	* m4/signal_h.m4 (gl_SIGNAL_H): Assume <signal.h> exists.
+	* m4/stdio_h.m4 (gl_STDIO_H): Assume <stdio.h> exists.
+	* m4/stdlib_h.m4 (gl_STDLIB_H): Assume <stdlib.h> exists.
+	* m4/string_h.m4 (gl_STRING_H): Assume <string.h> exists.
+	* tests/test-argp.c: Likewise.
+	* m4/time_h.m4 (gl_HEADER_TIME_H_BODY): Assume <time.h> exists.
+
 	multiarch: remove AA_APPLE_UNIVERSAL_BUILD
 	* m4/multiarch.m4 (gl_MULTIARCH): Don't AC_DEFINE
 	AA_APPLE_UNIVERSAL_BUILD.  See

--- a/README
+++ b/README
@@ -221,13 +221,16 @@
 
 Because we assume a freestanding C89 compiler, Gnulib code can include
 <float.h>, <limits.h>, <stdarg.h>, and <stddef.h> unconditionally.  It
-can also include hosted headers like <errno.h> that were present in
-Unix Version 7 and are thus widely available.  Similarly, many modules
-include <sys/types.h> even though it's not even in C99; that's OK
-since <sys/types.h> has been around nearly forever.  <string.h> and
+can also assume the existence of <ctime.h>, <errno.h>, <fcntl.h>,
+<locale.h>, <signal.h>, <stdio.h>, <stdlib.h>, <string.h>, and
+<time.h>.  Some of these headers, such as <errno.h>, were present in
+Unix Version 7 and are thus widely available.  <string.h> and
 <stdlib.h> were not in Unix Version 7, so they weren't universally
 available on ancient hosts, but they are both in SunOS 4 (the oldest
 platform still in relatively-common use) so Gnulib assumes them now.
+Similarly, many modules include <sys/types.h> even though it's not
+even in C99; that's OK since <sys/types.h> has been around nearly
+forever.
 
 Even if the include files exist, they may not conform to C89.
 However, GCC has a "fixincludes" script that attempts to fix most

--- a/lib/flock.c
+++ b/lib/flock.c
@@ -163,9 +163,7 @@
 #ifdef HAVE_STRUCT_FLOCK_L_TYPE
 /* We know how to implement flock in terms of fcntl. */
 
-#ifdef HAVE_FCNTL_H
 #include <fcntl.h>
-#endif
 
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>

--- a/lib/regex_internal.h
+++ b/lib/regex_internal.h
@@ -31,9 +31,7 @@
 #ifndef _LIBC
 # include "localcharset.h"
 #endif
-#if defined HAVE_LOCALE_H || defined _LIBC
-# include <locale.h>
-#endif
+#include <locale.h>
 
 #include <wchar.h>
 #include <wctype.h>
@@ -83,7 +81,7 @@
 # define SIZE_MAX ((size_t) -1)
 #endif
 
-#if (defined MB_CUR_MAX && HAVE_LOCALE_H && HAVE_WCTYPE_H && HAVE_ISWCTYPE && HAVE_WCSCOLL) || _LIBC
+#if (defined MB_CUR_MAX && HAVE_WCTYPE_H && HAVE_ISWCTYPE && HAVE_WCSCOLL) || _LIBC
 # define RE_ENABLE_I18N
 #endif
 

--- a/m4/ctype.m4
+++ b/m4/ctype.m4
@@ -1,4 +1,4 @@
-# ctype_h.m4 serial 5
+# ctype_h.m4 serial 6
 dnl Copyright (C) 2009-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -9,7 +9,7 @@
   AC_REQUIRE([gl_CTYPE_H_DEFAULTS])
 
   dnl <ctype.h> is always overridden, because of GNULIB_POSIXCHECK.
-  gl_CHECK_NEXT_HEADERS([ctype.h])
+  gl_NEXT_HEADERS([ctype.h])
 
   dnl Check for declarations of anything we want to poison if the
   dnl corresponding gnulib module is not in use.

--- a/m4/errno_h.m4
+++ b/m4/errno_h.m4
@@ -1,4 +1,4 @@
-# errno_h.m4 serial 7
+# errno_h.m4 serial 8
 dnl Copyright (C) 2004, 2006, 2008-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -50,7 +50,7 @@
   if test $gl_cv_header_errno_h_complete = yes; then
     ERRNO_H=''
   else
-    gl_CHECK_NEXT_HEADERS([errno.h])
+    gl_NEXT_HEADERS([errno.h])
     ERRNO_H='errno.h'
   fi
   AC_SUBST([ERRNO_H])

--- a/m4/fcntl_h.m4
+++ b/m4/fcntl_h.m4
@@ -1,4 +1,4 @@
-# serial 12
+# serial 13
 # Configure fcntl.h.
 dnl Copyright (C) 2006-2007, 2009-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
@@ -11,7 +11,7 @@
 [
   AC_REQUIRE([gl_FCNTL_H_DEFAULTS])
   AC_REQUIRE([gl_FCNTL_O_FLAGS])
-  gl_CHECK_NEXT_HEADERS([fcntl.h])
+  gl_NEXT_HEADERS([fcntl.h])
 
   dnl Check for declarations of anything we want to poison if the
   dnl corresponding gnulib module is not in use, if it is not common

--- a/m4/flock.m4
+++ b/m4/flock.m4
@@ -1,4 +1,4 @@
-# flock.m4 serial 1
+# flock.m4 serial 2
 dnl Copyright (C) 2008-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -19,7 +19,7 @@
 AC_DEFUN([gl_PREREQ_FLOCK],
 [
   AC_CHECK_FUNCS_ONCE([fcntl])
-  AC_CHECK_HEADERS_ONCE([unistd.h fcntl.h])
+  AC_CHECK_HEADERS_ONCE([unistd.h])
 
   dnl Do we have a POSIX fcntl lock implementation?
   AC_CHECK_MEMBERS([struct flock.l_type],[],[],[[#include <fcntl.h>]])

--- a/m4/locale_h.m4
+++ b/m4/locale_h.m4
@@ -1,4 +1,4 @@
-# locale_h.m4 serial 11
+# locale_h.m4 serial 12
 dnl Copyright (C) 2007, 2009-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -55,7 +55,7 @@
   AC_SUBST([HAVE_XLOCALE_H])
 
   dnl <locale.h> is always overridden, because of GNULIB_POSIXCHECK.
-  gl_CHECK_NEXT_HEADERS([locale.h])
+  gl_NEXT_HEADERS([locale.h])
 
   if test -n "$STDDEF_H" \
      || test $gl_cv_header_locale_h_posix2001 = no \

--- a/m4/regex.m4
+++ b/m4/regex.m4
@@ -1,4 +1,4 @@
-# serial 57
+# serial 58
 
 # Copyright (C) 1996-2001, 2003-2011 Free Software Foundation, Inc.
 #
@@ -13,8 +13,6 @@
 
 AC_DEFUN([gl_REGEX],
 [
-  AC_CHECK_HEADERS_ONCE([locale.h])
-
   AC_ARG_WITH([included-regex],
     [AS_HELP_STRING([--without-included-regex],
                     [don't compile regex; this is the default on systems
@@ -34,9 +32,7 @@
       [AC_RUN_IFELSE(
         [AC_LANG_PROGRAM(
           [AC_INCLUDES_DEFAULT[
-           #if HAVE_LOCALE_H
-            #include <locale.h>
-           #endif
+           #include <locale.h>
            #include <limits.h>
            #include <regex.h>
            ]],
@@ -47,31 +43,29 @@
             const char *s;
             struct re_registers regs;
 
-            #if HAVE_LOCALE_H
-              /* http://sourceware.org/ml/libc-hacker/2006-09/msg00008.html
-                 This test needs valgrind to catch the bug on Debian
-                 GNU/Linux 3.1 x86, but it might catch the bug better
-                 on other platforms and it shouldn't hurt to try the
-                 test here.  */
-              if (setlocale (LC_ALL, "en_US.UTF-8"))
-                {
-                  static char const pat[] = "insert into";
-                  static char const data[] =
-                    "\xFF\0\x12\xA2\xAA\xC4\xB1,K\x12\xC4\xB1*\xACK";
-                  re_set_syntax (RE_SYNTAX_GREP | RE_HAT_LISTS_NOT_NEWLINE
-                                 | RE_ICASE);
-                  memset (&regex, 0, sizeof regex);
-                  s = re_compile_pattern (pat, sizeof pat - 1, &regex);
-                  if (s)
-                    result |= 1;
-                  else if (re_search (&regex, data, sizeof data - 1,
-                                      0, sizeof data - 1, &regs)
-                           != -1)
-                    result |= 1;
-                  if (! setlocale (LC_ALL, "C"))
-                    return 1;
-                }
-            #endif
+            /* http://sourceware.org/ml/libc-hacker/2006-09/msg00008.html
+               This test needs valgrind to catch the bug on Debian
+               GNU/Linux 3.1 x86, but it might catch the bug better
+               on other platforms and it shouldn't hurt to try the
+               test here.  */
+            if (setlocale (LC_ALL, "en_US.UTF-8"))
+              {
+                static char const pat[] = "insert into";
+                static char const data[] =
+                  "\xFF\0\x12\xA2\xAA\xC4\xB1,K\x12\xC4\xB1*\xACK";
+                re_set_syntax (RE_SYNTAX_GREP | RE_HAT_LISTS_NOT_NEWLINE
+                               | RE_ICASE);
+                memset (&regex, 0, sizeof regex);
+                s = re_compile_pattern (pat, sizeof pat - 1, &regex);
+                if (s)
+                  result |= 1;
+                else if (re_search (&regex, data, sizeof data - 1,
+                                    0, sizeof data - 1, &regs)
+                         != -1)
+                  result |= 1;
+                if (! setlocale (LC_ALL, "C"))
+                  return 1;
+              }
 
             /* This test is from glibc bug 3957, reported by Andrew Mackey.  */
             re_set_syntax (RE_SYNTAX_EGREP | RE_HAT_LISTS_NOT_NEWLINE);

--- a/m4/signal_h.m4
+++ b/m4/signal_h.m4
@@ -7,7 +7,7 @@
 AC_DEFUN([gl_SIGNAL_H],
 [
   AC_REQUIRE([gl_SIGNAL_H_DEFAULTS])
-  gl_CHECK_NEXT_HEADERS([signal.h])
+  gl_NEXT_HEADERS([signal.h])
 # AIX declares sig_atomic_t to already include volatile, and C89 compilers
 # then choke on 'volatile sig_atomic_t'.  C99 requires that it compile.
   AC_CHECK_TYPE([volatile sig_atomic_t], [],

--- a/m4/stdio_h.m4
+++ b/m4/stdio_h.m4
@@ -9,7 +9,7 @@
   AC_REQUIRE([gl_STDIO_H_DEFAULTS])
   AC_REQUIRE([AC_C_INLINE])
   AC_REQUIRE([gl_ASM_SYMBOL_PREFIX])
-  gl_CHECK_NEXT_HEADERS([stdio.h])
+  gl_NEXT_HEADERS([stdio.h])
   dnl No need to create extra modules for these functions. Everyone who uses
   dnl <stdio.h> likely needs them.
   GNULIB_FPRINTF=1

--- a/m4/stdlib_h.m4
+++ b/m4/stdlib_h.m4
@@ -1,4 +1,4 @@
-# stdlib_h.m4 serial 33
+# stdlib_h.m4 serial 34
 dnl Copyright (C) 2007-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -7,7 +7,7 @@
 AC_DEFUN([gl_STDLIB_H],
 [
   AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
-  gl_CHECK_NEXT_HEADERS([stdlib.h])
+  gl_NEXT_HEADERS([stdlib.h])
   AC_CHECK_HEADERS([random.h], [], [], [AC_INCLUDES_DEFAULT])
   if test $ac_cv_header_random_h = yes; then
     HAVE_RANDOM_H=1

--- a/m4/string_h.m4
+++ b/m4/string_h.m4
@@ -5,7 +5,7 @@
 # gives unlimited permission to copy and/or distribute it,
 # with or without modifications, as long as this notice is preserved.
 
-# serial 18
+# serial 19
 
 # Written by Paul Eggert.
 
@@ -20,7 +20,7 @@
 [
   AC_REQUIRE([AC_C_RESTRICT])
   AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
-  gl_CHECK_NEXT_HEADERS([string.h])
+  gl_NEXT_HEADERS([string.h])
 
   dnl Check for declarations of anything we want to poison if the
   dnl corresponding gnulib module is not in use, and which is not

--- a/m4/time_h.m4
+++ b/m4/time_h.m4
@@ -2,7 +2,7 @@
 
 # Copyright (C) 2000-2001, 2003-2007, 2009-2011 Free Software Foundation, Inc.
 
-# serial 3
+# serial 4
 
 # This file is free software; the Free Software Foundation
 # gives unlimited permission to copy and/or distribute it,
@@ -21,7 +21,7 @@
 [
   AC_REQUIRE([AC_C_RESTRICT])
   AC_REQUIRE([gl_HEADER_TIME_H_DEFAULTS])
-  gl_CHECK_NEXT_HEADERS([time.h])
+  gl_NEXT_HEADERS([time.h])
   AC_REQUIRE([gl_CHECK_TYPE_STRUCT_TIMESPEC])
 ])
 

--- a/tests/test-argp.c
+++ b/tests/test-argp.c
@@ -21,9 +21,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
-#if HAVE_STRING_H
-# include <string.h>
-#endif
+#include <string.h>
 #if HAVE_STRINGS_H
 # include <strings.h>
 #endif