[glibc/zack/no-nested-includes] Limit the set of strings.h functions also exposed in string.h.

[Zack Weinberg <zack at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=94dda58a954e5a96d3ffefd25700661d25aa4dd9

commit 94dda58a954e5a96d3ffefd25700661d25aa4dd9
Author: Zack Weinberg <zackw@panix.com>
Date:   Sat Mar 16 21:01:12 2019 -0400

    Limit the set of strings.h functions also exposed in string.h.
    
    As someone who can remember when you might not be able to include both
    string.h and strings.h at the same time, I kinda resent that strings.h
    still exists and is the only standard source for str(n)casecmp(_l) and
    ffs.  I think itâ??s right that we expose those functions from string.h.
    However, thereâ??s no reason we need to keep exposing the other obsolete
    functions that strings.h declares from string.h.
    
    This patch creates <bits/strings_x2k8.h>, which declares the
    non-obsolete functions whose official home is strings.h.  strings.h
    includes it unconditionally, and string.h includes it under
    __USE_MISC, instead of strings.h.
    
    Two tests of the obsolete strings.h functions had to be adjusted.
    
    	* string/strings.h (strcasecmp, strncasecmp, strcasecmp_l)
    	(strncasecmp_l, ffs, ffsl, ffsll): Move declarations to...
    	* string/bits/strings_x2k8.h: ... this new file.
    	* string/Makefile: Install bits/strings_x2k8.h.
    	* include/bits/strings_x2k8h: New wrapper.
    	* string/string.h: Include bits/strings_x2k8.h instead of
    	strings.h.
    
    	* debug/tst-chk1.c, string/test-string.h: Include strings.h.
    	* scripts/check-obsolete-constructs.py: string.h is no longer
    	expected to include strings.h.

Diff:
---
 NEWS                                 |  3 ++
 debug/tst-chk1.c                     |  1 +
 include/bits/strings_x2k8.h          |  1 +
 scripts/check-obsolete-constructs.py |  1 -
 string/Makefile                      |  2 +-
 string/bits/strings_x2k8.h           | 70 ++++++++++++++++++++++++++++++++++++
 string/string.h                      |  2 +-
 string/strings.h                     | 39 ++------------------
 string/test-string.h                 |  1 +
 9 files changed, 80 insertions(+), 40 deletions(-)

diff --git a/NEWS b/NEWS
index 3dace08..25bf198 100644
--- a/NEWS
+++ b/NEWS
@@ -45,6 +45,9 @@ Deprecated and removed features, and other changes affecting compatibility:
 * The obsolete and never-implemented XSI STREAMS header files <stropts.h>
   and <sys/stropts.h> have been removed.
 
+* The obsolete functions bcmp, bcopy, bzero, index, and rindex are no
+  longer declared in <string.h>, only <strings.h>.
+
 * The typedefs u_int8_t, u_int16_t, u_int32_t, u_int64_t, and register_t
   are no longer defined by <sys/types.h> in strict conformance modes.
   These types were historically provided by <sys/types.h> on BSD systems,
diff --git a/debug/tst-chk1.c b/debug/tst-chk1.c
index c6f11af..014b08f 100644
--- a/debug/tst-chk1.c
+++ b/debug/tst-chk1.c
@@ -30,6 +30,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <unistd.h>
 #include <wchar.h>
 #include <sys/poll.h>
diff --git a/include/bits/strings_x2k8.h b/include/bits/strings_x2k8.h
new file mode 100644
index 0000000..7eddd92
--- /dev/null
+++ b/include/bits/strings_x2k8.h
@@ -0,0 +1 @@
+#include <string/bits/strings_x2k8.h>
diff --git a/scripts/check-obsolete-constructs.py b/scripts/check-obsolete-constructs.py
index a06e986..9bda57f 100755
--- a/scripts/check-obsolete-constructs.py
+++ b/scripts/check-obsolete-constructs.py
@@ -514,7 +514,6 @@ HEADER_ALLOWED_INCLUDES = {
     "inttypes.h":                  [ "stdint.h" ],
     "signal.h":                    [ "sys/ucontext.h" ],
     "stdlib.h":                    [ "alloca.h", "sys/types.h" ],
-    "string.h":                    [ "strings.h" ],
     "tgmath.h":                    [ "complex.h", "math.h" ],
     "threads.h":                   [ "time.h" ],
 
diff --git a/string/Makefile b/string/Makefile
index 3e5721e..c9ebede 100644
--- a/string/Makefile
+++ b/string/Makefile
@@ -23,7 +23,7 @@ subdir	:= string
 include ../Makeconfig
 
 headers		:= string.h bits/string_fortified.h			\
-		   strings.h bits/strings_fortified.h			\
+		   strings.h bits/strings_x2k8.h bits/strings_fortified.h \
 		   byteswap.h bits/byteswap.h				\
 		   endian.h bits/endian.h bits/endianness.h		\
 		   bits/uintn-identity.h				\
diff --git a/string/bits/strings_x2k8.h b/string/bits/strings_x2k8.h
new file mode 100644
index 0000000..dbcb0b2
--- /dev/null
+++ b/string/bits/strings_x2k8.h
@@ -0,0 +1,70 @@
+/* Copyright (C) 2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _BITS_STRINGS_X2K8_H
+#define _BITS_STRINGS_X2K8_H 1
+
+/* This header file declares all of the strings.h functions that are
+   not marked as "obsolete" in POSIX.1-2008.  As a GNU extension,
+   these functions are also made available via string.h.  */
+
+#if !defined _STRING_H && !defined _STRINGS_H
+# error "Never include <bits/strings_x2k8.h> directly, use <string(s).h>."
+#endif
+
+__BEGIN_DECLS
+
+/* Compare S1 and S2, ignoring case.  */
+extern int strcasecmp (const char *__s1, const char *__s2)
+     __THROW __attribute_pure__ __nonnull ((1, 2));
+
+/* Compare no more than N chars of S1 and S2, ignoring case.  */
+extern int strncasecmp (const char *__s1, const char *__s2, size_t __n)
+     __THROW __attribute_pure__ __nonnull ((1, 2));
+
+#ifdef	__USE_XOPEN2K8
+/* POSIX.1-2008 extended locale interface (see locale.h).  */
+# include <bits/types/locale_t.h>
+
+/* Compare S1 and S2, ignoring case, using collation rules from LOC.  */
+extern int strcasecmp_l (const char *__s1, const char *__s2, locale_t __loc)
+     __THROW __attribute_pure__ __nonnull ((1, 2, 3));
+
+/* Compare no more than N chars of S1 and S2, ignoring case, using
+   collation rules from LOC.  */
+extern int strncasecmp_l (const char *__s1, const char *__s2,
+			  size_t __n, locale_t __loc)
+     __THROW __attribute_pure__ __nonnull ((1, 2, 4));
+#endif
+
+#if defined __USE_MISC || !defined __USE_XOPEN2K8 || defined __USE_XOPEN2K8XSI
+/* Return the position of the first bit set in I, or 0 if none are set.
+   The least-significant bit is position 1, the most-significant 32.  */
+extern int ffs (int __i) __THROW __attribute_const__;
+#endif
+
+/* The following two functions are non-standard but necessary for non-32 bit
+   platforms.  */
+#ifdef	__USE_MISC
+extern int ffsl (long int __l) __THROW __attribute_const__;
+__extension__ extern int ffsll (long long int __ll)
+     __THROW __attribute_const__;
+#endif
+
+__END_DECLS
+
+#endif /* bits/strings_x2k8.h */
diff --git a/string/string.h b/string/string.h
index c38eea9..6b25243 100644
--- a/string/string.h
+++ b/string/string.h
@@ -428,7 +428,7 @@ extern char *strerror_l (int __errnum, locale_t __l) __THROW;
 #endif
 
 #ifdef __USE_MISC
-# include <strings.h>
+# include <bits/strings_x2k8.h>
 
 /* Set N bytes of S to 0.  The compiler will not delete a call to this
    function, even if S is dead after the call.  */
diff --git a/string/strings.h b/string/strings.h
index 5428bc4..8f380bf 100644
--- a/string/strings.h
+++ b/string/strings.h
@@ -22,6 +22,8 @@
 #define __need_size_t
 #include <stddef.h>
 
+#include <bits/strings_x2k8.h>
+
 /* Tell the caller that we provide correct C++ prototypes.  */
 #if defined __cplusplus && __GNUC_PREREQ (4, 4)
 # define __CORRECT_ISO_CPP_STRINGS_H_PROTO
@@ -98,43 +100,6 @@ extern char *rindex (const char *__s, int __c)
 # endif
 #endif
 
-#if defined __USE_MISC || !defined __USE_XOPEN2K8 || defined __USE_XOPEN2K8XSI
-/* Return the position of the first bit set in I, or 0 if none are set.
-   The least-significant bit is position 1, the most-significant 32.  */
-extern int ffs (int __i) __THROW __attribute_const__;
-#endif
-
-/* The following two functions are non-standard but necessary for non-32 bit
-   platforms.  */
-# ifdef	__USE_MISC
-extern int ffsl (long int __l) __THROW __attribute_const__;
-__extension__ extern int ffsll (long long int __ll)
-     __THROW __attribute_const__;
-# endif
-
-/* Compare S1 and S2, ignoring case.  */
-extern int strcasecmp (const char *__s1, const char *__s2)
-     __THROW __attribute_pure__ __nonnull ((1, 2));
-
-/* Compare no more than N chars of S1 and S2, ignoring case.  */
-extern int strncasecmp (const char *__s1, const char *__s2, size_t __n)
-     __THROW __attribute_pure__ __nonnull ((1, 2));
-
-#ifdef	__USE_XOPEN2K8
-/* POSIX.1-2008 extended locale interface (see locale.h).  */
-# include <bits/types/locale_t.h>
-
-/* Compare S1 and S2, ignoring case, using collation rules from LOC.  */
-extern int strcasecmp_l (const char *__s1, const char *__s2, locale_t __loc)
-     __THROW __attribute_pure__ __nonnull ((1, 2, 3));
-
-/* Compare no more than N chars of S1 and S2, ignoring case, using
-   collation rules from LOC.  */
-extern int strncasecmp_l (const char *__s1, const char *__s2,
-			  size_t __n, locale_t __loc)
-     __THROW __attribute_pure__ __nonnull ((1, 2, 4));
-#endif
-
 __END_DECLS
 
 #if __GNUC_PREREQ (3,4) && __USE_FORTIFY_LEVEL > 0 \
diff --git a/string/test-string.h b/string/test-string.h
index befd3e9..2c1c016 100644
--- a/string/test-string.h
+++ b/string/test-string.h
@@ -55,6 +55,7 @@ extern impl_t __start_impls[], __stop_impls[];
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <sys/mman.h>
 #include <sys/param.h>
 #include <unistd.h>