move __BYTE_ORDER definition to alltypes.h

this change is motivated by the intersection of several factors.
presently, despite being a nonstandard header, endian.h is exposing
the unprefixed byte order macros and functions only if _BSD_SOURCE or
_GNU_SOURCE is defined. this is to accommodate use of endian.h from
other headers, including bits headers, which need to define structure
layout in terms of endianness. with time64 switch-over, even more
headers will need to do this.

at the same time, the resolution of Austin Group issue 162 makes
endian.h a standard header for POSIX-future, requiring that it expose
the unprefixed macros and the functions even in standards-conforming
profiles. changes to meet this new requirement would break existing
internal usage of endian.h by causing it to violate namespace where
it's used.

instead, have the arch's alltypes.h define __BYTE_ORDER, either as a
fixed constant or depending on the right arch-specific predefined
macros for determining endianness. explicit literals 1234 and 4321 are
used instead of __LITTLE_ENDIAN and __BIG_ENDIAN so that there's no
danger of getting the wrong result if a macro is undefined and
implicitly evaluates to 0 at the preprocessor level.

the powerpc (32-bit) bits/endian.h being removed had logic for varying
endianness, but our powerpc arch has never supported that and has
always been big-endian-only. this logic is not carried over to the new
__BYTE_ORDER definition in alltypes.h.

arch/aarch64/bits/alltypes.h.in

@@ -2,6 +2,12 @@
 #define _Int64 long
 #define _Reg long
 
+#if __AARCH64EB__
+#define __BYTE_ORDER 4321
+#else
+#define __BYTE_ORDER 1234
+#endif
+
 #ifndef __cplusplus
 TYPEDEF unsigned wchar_t;
 #endif

arch/aarch64/bits/endian.h

-#if __AARCH64EB__
-#define __BYTE_ORDER __BIG_ENDIAN
-#else
-#define __BYTE_ORDER __LITTLE_ENDIAN
-#endif

arch/arm/bits/alltypes.h.in

@@ -2,6 +2,12 @@
 #define _Int64 long long
 #define _Reg int
 
+#if __ARMEB__
+#define __BYTE_ORDER 4321
+#else
+#define __BYTE_ORDER 1234
+#endif
+
 #ifndef __cplusplus
 TYPEDEF unsigned wchar_t;
 #endif

arch/arm/bits/endian.h

-#if __ARMEB__
-#define __BYTE_ORDER __BIG_ENDIAN
-#else
-#define __BYTE_ORDER __LITTLE_ENDIAN
-#endif

arch/i386/bits/alltypes.h.in

@@ -2,6 +2,8 @@
 #define _Int64 long long
 #define _Reg int
 
+#define __BYTE_ORDER 1234
+
 #ifndef __cplusplus
 #ifdef __WCHAR_TYPE__
 TYPEDEF __WCHAR_TYPE__ wchar_t;

arch/i386/bits/endian.h

-#define __BYTE_ORDER __LITTLE_ENDIAN

arch/m68k/bits/alltypes.h.in

@@ -2,6 +2,8 @@
 #define _Int64 long long
 #define _Reg int
 
+#define __BYTE_ORDER 4321
+
 #ifndef __cplusplus
 #ifdef __WCHAR_TYPE__
 TYPEDEF __WCHAR_TYPE__ wchar_t;

arch/m68k/bits/endian.h

-#define __BYTE_ORDER __BIG_ENDIAN

arch/microblaze/bits/alltypes.h.in

@@ -2,6 +2,12 @@
 #define _Int64 long long
 #define _Reg int
 
+#if __MICROBLAZEEL__
+#define __BYTE_ORDER 1234
+#else
+#define __BYTE_ORDER 4321
+#endif
+
 #ifndef __cplusplus
 TYPEDEF int wchar_t;
 #endif

arch/microblaze/bits/endian.h

-#if __MICROBLAZEEL__
-#define __BYTE_ORDER __LITTLE_ENDIAN
-#else
-#define __BYTE_ORDER __BIG_ENDIAN
-#endif

arch/mips/bits/alltypes.h.in

@@ -2,6 +2,12 @@
 #define _Int64 long long
 #define _Reg int
 
+#if _MIPSEL || __MIPSEL || __MIPSEL__
+#define __BYTE_ORDER 1234
+#else
+#define __BYTE_ORDER 4321
+#endif
+
 #ifndef __cplusplus
 TYPEDEF int wchar_t;
 #endif

arch/mips/bits/endian.h

-#if _MIPSEL || __MIPSEL || __MIPSEL__
-#define __BYTE_ORDER __LITTLE_ENDIAN
-#else
-#define __BYTE_ORDER __BIG_ENDIAN
-#endif

arch/mips64/bits/alltypes.h.in

@@ -2,6 +2,12 @@
 #define _Int64 long
 #define _Reg long
 
+#if _MIPSEL || __MIPSEL || __MIPSEL__
+#define __BYTE_ORDER 1234
+#else
+#define __BYTE_ORDER 4321
+#endif
+
 #ifndef __cplusplus
 TYPEDEF int wchar_t;
 #endif

arch/mips64/bits/endian.h

-#if _MIPSEL || __MIPSEL || __MIPSEL__
-#define __BYTE_ORDER __LITTLE_ENDIAN
-#else
-#define __BYTE_ORDER __BIG_ENDIAN
-#endif

arch/mipsn32/bits/alltypes.h.in

@@ -2,6 +2,12 @@
 #define _Int64 long long
 #define _Reg int
 
+#if _MIPSEL || __MIPSEL || __MIPSEL__
+#define __BYTE_ORDER 1234
+#else
+#define __BYTE_ORDER 4321
+#endif
+
 #ifndef __cplusplus
 TYPEDEF int wchar_t;
 #endif

arch/mipsn32/bits/endian.h

-#if _MIPSEL || __MIPSEL || __MIPSEL__
-#define __BYTE_ORDER __LITTLE_ENDIAN
-#else
-#define __BYTE_ORDER __BIG_ENDIAN
-#endif

arch/or1k/bits/alltypes.h.in

@@ -2,6 +2,8 @@
 #define _Int64 long long
 #define _Reg int
 
+#define __BYTE_ORDER 4321
+
 #ifndef __cplusplus
 TYPEDEF unsigned wchar_t;
 #endif

arch/or1k/bits/endian.h

-#define __BYTE_ORDER __BIG_ENDIAN

arch/powerpc/bits/alltypes.h.in

@@ -2,6 +2,8 @@
 #define _Int64 long long
 #define _Reg int
 
+#define __BYTE_ORDER 4321
+
 #ifndef __cplusplus
 #ifdef __WCHAR_TYPE__
 TYPEDEF __WCHAR_TYPE__ wchar_t;

arch/powerpc/bits/endian.h

-#ifdef __BIG_ENDIAN__
-  #if __BIG_ENDIAN__
-    #define __BYTE_ORDER __BIG_ENDIAN
-  #endif
-#endif /* __BIG_ENDIAN__ */
-
-#ifdef __LITTLE_ENDIAN__
-  #if __LITTLE_ENDIAN__
-    #define __BYTE_ORDER __LITTLE_ENDIAN
-  #endif
-#endif /* __LITTLE_ENDIAN__ */
-
-#ifndef __BYTE_ORDER
-  #define __BYTE_ORDER __BIG_ENDIAN
-#endif

arch/powerpc64/bits/alltypes.h.in

@@ -2,6 +2,12 @@
 #define _Int64 long
 #define _Reg long
 
+#if __BIG_ENDIAN__
+#define __BYTE_ORDER 4321
+#else
+#define __BYTE_ORDER 1234
+#endif
+
 #ifndef __cplusplus
 TYPEDEF int wchar_t;
 #endif

arch/powerpc64/bits/endian.h

-#if __BIG_ENDIAN__
-#define __BYTE_ORDER __BIG_ENDIAN
-#else
-#define __BYTE_ORDER __LITTLE_ENDIAN
-#endif

arch/riscv64/bits/alltypes.h.in

@@ -2,6 +2,8 @@
 #define _Int64 long
 #define _Reg long
 
+#define __BYTE_ORDER 1234
+
 #ifndef __cplusplus
 TYPEDEF int wchar_t;
 #endif

arch/riscv64/bits/endian.h

-#define __BYTE_ORDER __LITTLE_ENDIAN

arch/s390x/bits/alltypes.h.in

@@ -2,6 +2,8 @@
 #define _Int64 long
 #define _Reg long
 
+#define __BYTE_ORDER 4321
+
 #ifndef __cplusplus
 TYPEDEF int wchar_t;
 #endif

arch/s390x/bits/endian.h

-#define __BYTE_ORDER __BIG_ENDIAN

arch/sh/bits/alltypes.h.in

@@ -2,6 +2,12 @@
 #define _Int64 long long
 #define _Reg int
 
+#if __BIG_ENDIAN__
+#define __BYTE_ORDER 4321
+#else
+#define __BYTE_ORDER 1234
+#endif
+
 #ifndef __cplusplus
 #ifdef __WCHAR_TYPE__
 TYPEDEF __WCHAR_TYPE__ wchar_t;

arch/sh/bits/endian.h

-#if __BIG_ENDIAN__
-#define __BYTE_ORDER __BIG_ENDIAN
-#else
-#define __BYTE_ORDER __LITTLE_ENDIAN
-#endif

arch/x32/bits/alltypes.h.in

@@ -2,6 +2,8 @@
 #define _Int64 long long
 #define _Reg long long
 
+#define __BYTE_ORDER 1234
+
 #ifndef __cplusplus
 #ifdef __WCHAR_TYPE__
 TYPEDEF __WCHAR_TYPE__ wchar_t;

arch/x32/bits/endian.h

-#define __BYTE_ORDER __LITTLE_ENDIAN

arch/x86_64/bits/alltypes.h.in

@@ -2,6 +2,8 @@
 #define _Int64 long
 #define _Reg long
 
+#define __BYTE_ORDER 1234
+
 #ifndef __cplusplus
 TYPEDEF int wchar_t;
 #endif

arch/x86_64/bits/endian.h

-#define __BYTE_ORDER __LITTLE_ENDIAN

include/alltypes.h.in

+#define __LITTLE_ENDIAN 1234
+#define __BIG_ENDIAN 4321
+
 TYPEDEF unsigned _Addr size_t;
 TYPEDEF unsigned _Addr uintptr_t;
 TYPEDEF _Addr ptrdiff_t;

include/endian.h

@@ -3,15 +3,9 @@
 
 #include <features.h>
 
-#define __LITTLE_ENDIAN 1234
-#define __BIG_ENDIAN 4321
 #define __PDP_ENDIAN 3412
 
-#if defined(__GNUC__) && defined(__BYTE_ORDER__)
-#define __BYTE_ORDER __BYTE_ORDER__
-#else
-#include <bits/endian.h>
-#endif
+#include <bits/alltypes.h>
 
 #if defined(_GNU_SOURCE) || defined(_BSD_SOURCE)