Split up endian.h to minimize exposure of BYTE_ORDER.

With only two exceptions (sys/types.h and sys/param.h, both of which
historically might have defined BYTE_ORDER) the public headers that
include <endian.h> only want to be able to test __BYTE_ORDER against
__*_ENDIAN.

This patch creates a new bits/endian.h that can be included by any
header that wants to be able to test __BYTE_ORDER and/or
__FLOAT_WORD_ORDER against the __*_ENDIAN constants, or needs
__LONG_LONG_PAIR.  It only defines macros in the implementation
namespace.

The existing bits/endian.h (which could not be included independently
of endian.h, and only defines __BYTE_ORDER and maybe __FLOAT_WORD_ORDER)
is renamed to bits/endianness.h.  I also took the opportunity to
canonicalize the form of this header, which we are stuck with having
one copy of per architecture.  Since they are so short, this means git
doesn’t understand that they were renamed from existing headers, sigh.

endian.h itself is a nonstandard header and its only remaining use
from a standard header is guarded by __USE_MISC, so I dropped the
__USE_MISC conditionals from around all of the public-namespace things
it defines.  (This means, an application that requests strict library
conformance but includes endian.h will still see the definition of
BYTE_ORDER.)

A few changes to specific bits/endian(ness).h variants deserve
mention:

 - sysdeps/unix/sysv/linux/ia64/bits/endian.h is moved to
   sysdeps/ia64/bits/endianness.h.  If I remember correctly, ia64 did
   have selectable endianness, but we have assembly code in
   sysdeps/ia64 that assumes it’s little-endian, so there is no reason
   to treat the ia64 endianness.h as linux-specific.

 - The C-SKY port does not fully support big-endian mode, but I do
   not think this is sufficient reason to make csky/bits/endian(ness).h
   error out if __CSKYBE__ is defined, so it now defines __BYTE_ORDER
   appropriately for whichever mode the compiler is in.

 - The PowerPC port had extra logic in its bits/endian.h to detect a
   broken compiler, which strikes me as unnecessary, so I removed it.

 - The only files that defined __FLOAT_WORD_ORDER always defined it to
   the same value as __BYTE_ORDER, so I removed those definitions.
   The SH bits/endian(ness).h had comments inconsistent with the
   actual setting of __FLOAT_WORD_ORDER, which I also removed.

 - I *removed* copyright boilerplate from the few bits/endian(ness).h
   headers that had it; these files record a single fact in a fashion
   dictated by an external spec, so I do not think they are copyrightable.

As long as I was changing every copy of ieee754.h in the tree, I
noticed that only the MIPS variant includes float.h, because it uses
LDBL_MANT_DIG to decide among three different versions of
ieee854_long_double.  This patch makes it not include float.h when
GCC’s intrinsic __LDBL_MANT_DIG__ is available.

	* string/endian.h: Unconditionally define LITTLE_ENDIAN,
	BIG_ENDIAN, PDP_ENDIAN, and BYTE_ORDER.	 Condition byteswapping
	macros only on !__ASSEMBLER__.	Move the definitions of
	__BIG_ENDIAN, __LITTLE_ENDIAN, __PDP_ENDIAN, __FLOAT_WORD_ORDER,
	and __LONG_LONG_PAIR to...
	* string/bits/endian.h: ...this new file, which includes
	the renamed header bits/endianness.h for the definition of
	__BYTE_ORDER and possibly __FLOAT_WORD_ORDER.

	* string/Makefile: Install bits/endianness.h.
	* include/bits/endian.h: New wrapper.

	* bits/endian.h: Rename to bits/endianness.h.
	Add multiple-include guard.  Rewrite the comment explaining what
	the machine-specific variants of this file should do.

	* sysdeps/unix/sysv/linux/ia64/bits/endian.h:
	Move to sysdeps/ia64.

	* sysdeps/aarch64/bits/endian.h
	* sysdeps/alpha/bits/endian.h
	* sysdeps/arm/bits/endian.h
	* sysdeps/csky/bits/endian.h
	* sysdeps/hppa/bits/endian.h
	* sysdeps/ia64/bits/endian.h
	* sysdeps/m68k/bits/endian.h
	* sysdeps/microblaze/bits/endian.h
	* sysdeps/mips/bits/endian.h
	* sysdeps/nios2/bits/endian.h
	* sysdeps/powerpc/bits/endian.h
	* sysdeps/riscv/bits/endian.h
	* sysdeps/s390/bits/endian.h
	* sysdeps/sh/bits/endian.h
	* sysdeps/sparc/bits/endian.h
	* sysdeps/x86/bits/endian.h:
	Rename to endianness.h; canonicalize form of file; remove
	redundant definitions of __FLOAT_WORD_ORDER.

	* sysdeps/csky/bits/endianness.h: Do not error out if __CSKYEB__
	is defined.
	* sysdeps/powerpc/bits/endianness.h: Remove logic to check for
	broken compilers.

	* ctype/ctype.h
	* inet/netinet/in.h
	* resolv/arpa/nameser_compat.h
	* sysdeps/aarch64/nptl/bits/pthreadtypes-arch.h
	* sysdeps/arm/nptl/bits/pthreadtypes-arch.h
	* sysdeps/csky/nptl/bits/pthreadtypes-arch.h
	* sysdeps/ia64/ieee754.h
	* sysdeps/ieee754/ieee754.h
	* sysdeps/ieee754/ldbl-128/ieee754.h
	* sysdeps/ieee754/ldbl-128ibm/ieee754.h
	* sysdeps/m68k/nptl/bits/pthreadtypes-arch.h
	* sysdeps/microblaze/nptl/bits/pthreadtypes-arch.h
	* sysdeps/mips/ieee754/ieee754.h
	* sysdeps/mips/nptl/bits/pthreadtypes-arch.h
	* sysdeps/nios2/nptl/bits/pthreadtypes-arch.h
	* sysdeps/nptl/pthread.h
	* sysdeps/riscv/nptl/bits/pthreadtypes-arch.h
	* sysdeps/sh/nptl/bits/pthreadtypes-arch.h
	* sysdeps/sparc/sparc32/ieee754.h
	* sysdeps/unix/sysv/linux/generic/bits/stat.h
	* sysdeps/unix/sysv/linux/generic/bits/statfs.h
	* sysdeps/unix/sysv/linux/sys/acct.h
	* wctype/bits/wctype-wchar.h:
	Include bits/endian.h, not endian.h.

	* sysdeps/unix/sysv/linux/hppa/pthread.h: Don’t include endian.h.

	* sysdeps/mips/ieee754/ieee754.h: Use __LDBL_MANT_DIG__
	in ifdefs, instead of LDBL_MANT_DIG.  Only include float.h
	when __LDBL_MANT_DIG__ is not predefined, in which case
	define __LDBL_MANT_DIG__ to equal LDBL_MANT_DIG.

	* scripts/check-obsolete-constructs.h: Remove most of the
	whitelist entries for endian.h and float.h.

7 files changed, 27 insertions, 31 deletions

diff --git a/bits/endian.h b/bits/endian.h
deleted file mode 100644
index 45afd4ae47..0000000000
--- a/bits/endian.h
+++ /dev/null
@@ -1,13 +0,0 @@
-/* This file should define __BYTE_ORDER as appropriate for the machine
-   in question.  See string/endian.h for how to define it.
-
-   If only the stub bits/endian.h applies to a particular configuration,
-   bytesex.h is generated by running a program on the host machine.
-   So if cross-compiling to a machine with a different byte order,
-   the bits/endian.h file for that machine must exist.  */
-
-#ifndef _ENDIAN_H
-# error "Never use <bits/endian.h> directly; include <endian.h> instead."
-#endif
-
-#error Machine byte order unknown.
diff --git a/bits/endianness.h b/bits/endianness.h
new file mode 100644
index 0000000000..b83040ddec
--- /dev/null
+++ b/bits/endianness.h
@@ -0,0 +1,17 @@
+/* This file must be overridden for each supported CPU architecture.
+   It should define __BYTE_ORDER to one of the constants defined in
+   string/bits/endian.h, as appropriate for the machine in
+   question.  If floating-point quantities are not stored in the
+   same byte order as integer quantities, it should also define
+   __FLOAT_WORD_ORDER as appropriate.  */
+
+#ifndef _BITS_ENDIANNESS_H
+#define _BITS_ENDIANNESS_H 1
+
+#ifndef _BITS_ENDIAN_H
+# error "Never use <bits/endianness.h> directly; include <endian.h> instead."
+#endif
+
+#error "Machine byte order unknown."
+
+#endif /* bits/endianness.h */
diff --git a/inet/netinet/in.h b/inet/netinet/in.h
index 95eaf68dfe..993cfe6ae8 100644
--- a/inet/netinet/in.h
+++ b/inet/netinet/in.h
@@ -380,9 +380,9 @@ extern uint32_t htonl (uint32_t __hostlong)
 extern uint16_t htons (uint16_t __hostshort)
      __THROW __attribute__ ((__const__));
 
-#include <endian.h>
 
 /* Get machine dependent optimized versions of byte swapping functions.  */
+#include <bits/endian.h>
 #include <bits/byteswap.h>
 #include <bits/uintn-identity.h>
 
diff --git a/resolv/arpa/nameser_compat.h b/resolv/arpa/nameser_compat.h
index f1c390f3b9..37c178b524 100644
--- a/resolv/arpa/nameser_compat.h
+++ b/resolv/arpa/nameser_compat.h
@@ -29,7 +29,7 @@
 #ifndef _ARPA_NAMESER_COMPAT_
 #define	_ARPA_NAMESER_COMPAT_
 
-#include <endian.h>
+#include <bits/endian.h>
 
 /*%
  * Structure for query header.  The order of the fields is machine- and
diff --git a/scripts/check-obsolete-constructs.py b/scripts/check-obsolete-constructs.py
index 25c0d6868d..8b52463cfb 100755
--- a/scripts/check-obsolete-constructs.py
+++ b/scripts/check-obsolete-constructs.py
@@ -511,7 +511,6 @@ HEADER_ALLOWED_INCLUDES = {
     # mandated: inttypes.h -> stdint.h
     #           tgmath.h   -> complex.h, math.h
     #           threads.h  -> time.h
-    "ctype.h":                     [ "endian.h" ],
     "inttypes.h":                  [ "stdint.h" ],
     "signal.h":                    [ "sys/ucontext.h" ],
     "stdlib.h":                    [ "alloca.h", "sys/types.h" ],
@@ -557,7 +556,7 @@ HEADER_ALLOWED_INCLUDES = {
     "netdb.h":                     [ "netinet/in.h", "rpc/netdb.h" ],
     "arpa/inet.h":                 [ "netinet/in.h" ],
     "net/if.h":                    [ "sys/socket.h", "sys/types.h" ],
-    "netinet/in.h":                [ "endian.h", "sys/socket.h" ],
+    "netinet/in.h":                [ "sys/socket.h" ],
     "netinet/tcp.h":               [ "stdint.h", "sys/socket.h",
                                      "sys/types.h" ],
 
@@ -570,7 +569,7 @@ HEADER_ALLOWED_INCLUDES = {
     "envz.h":                      [ "argz.h", "errno.h" ],
     "fts.h":                       [ "sys/types.h" ],
     "gshadow.h":                   [ "paths.h" ],
-    "ieee754.h":                   [ "endian.h", "float.h" ],
+    "ieee754.h":                   [ "float.h" ],
     "lastlog.h":                   [ "utmp.h" ],
     "libintl.h":                   [ "locale.h" ],
     "link.h":                      [ "dlfcn.h", "elf.h", "sys/types.h" ],
@@ -651,7 +650,6 @@ HEADER_ALLOWED_INCLUDES = {
 
     "arpa/nameser.h":              [ "arpa/nameser_compat.h", "stdint.h",
                                      "sys/param.h", "sys/types.h" ],
-    "arpa/nameser_compat.h":       [ "endian.h" ],
     "net/ethernet.h":              [ "stdint.h", "sys/types.h",
                                      "net/if_ether.h" ],
     "net/if_arp.h":                [ "stdint.h", "sys/socket.h",
@@ -693,15 +691,11 @@ HEADER_ALLOWED_INCLUDES = {
     "bits/fcntl.h":                [ "sys/types.h" ],
     "bits/ipc.h":                  [ "sys/types.h" ],
     "bits/procfs.h":               [ "signal.h", "sys/ucontext.h" ],
-    "bits/pthreadtypes-arch.h":    [ "endian.h" ],
     "bits/sem.h":                  [ "sys/types.h" ],
     "bits/socket.h":               [ "sys/types.h" ],
-    "bits/stat.h":                 [ "endian.h" ],
-    "bits/statfs.h":               [ "endian.h" ],
     "bits/types/res_state.h":      [ "netinet/in.h", "sys/types.h" ],
     "bits/utmp.h":                 [ "paths.h", "sys/time.h", "sys/types.h" ],
     "bits/utmpx.h":                [ "paths.h", "sys/time.h" ],
-    "bits/wctype-wchar.h":         [ "endian.h" ],
 }
 
 # As above, but each group of whitelist entries is only used for
diff --git a/string/endian.h b/string/endian.h
index 0256ee4446..63363f8c6c 100644
--- a/string/endian.h
+++ b/string/endian.h
@@ -23,14 +23,12 @@
 /* Get the definitions of __*_ENDIAN, __BYTE_ORDER, and __FLOAT_WORD_ORDER.  */
 #include <bits/endian.h>
 
-#ifdef __USE_MISC
-# define LITTLE_ENDIAN	__LITTLE_ENDIAN
-# define BIG_ENDIAN	__BIG_ENDIAN
-# define PDP_ENDIAN	__PDP_ENDIAN
-# define BYTE_ORDER	__BYTE_ORDER
-#endif
+#define LITTLE_ENDIAN	__LITTLE_ENDIAN
+#define BIG_ENDIAN	__BIG_ENDIAN
+#define PDP_ENDIAN	__PDP_ENDIAN
+#define BYTE_ORDER	__BYTE_ORDER
 
-#if defined __USE_MISC && !defined __ASSEMBLER__
+#ifndef __ASSEMBLER__
 /* Conversion interfaces.  */
 # include <bits/byteswap.h>
 # include <bits/uintn-identity.h>
diff --git a/sysdeps/mips/ieee754/ieee754.h b/sysdeps/mips/ieee754/ieee754.h
index 75059f733b..62f17586f1 100644
--- a/sysdeps/mips/ieee754/ieee754.h
+++ b/sysdeps/mips/ieee754/ieee754.h
@@ -24,7 +24,7 @@
 
 #ifndef __LDBL_MANT_DIG__
 # include <float.h>
-# define __LDBL_MANT_DIG__ __LDBL_MANT_DIG__
+# define __LDBL_MANT_DIG__ LDBL_MANT_DIG
 #endif
 
 __BEGIN_DECLS