Issue #16166: Add PY_LITTLE_ENDIAN and PY_BIG_ENDIAN macros and unified

endianess detection and handling.

15 files changed, 79 insertions, 108 deletions

diff --git a/Include/pyport.h b/Include/pyport.h
index 284e6da..baa04fe 100644
--- a/Include/pyport.h
+++ b/Include/pyport.h
@@ -865,4 +865,18 @@ extern pid_t forkpty(int *, char *, struct termios *, struct winsize *);
 #endif
 #endif
 
+/*
+ * Convenient macros to deal with endianess of the platform. WORDS_BIGENDIAN is
+ * detected by configure and defined in pyconfig.h. The code in pyconfig.h
+ * also also takes care of Apple's universal builds.
+ */
+
+#ifdef WORDS_BIGENDIAN
+#define PY_BIG_ENDIAN 1
+#define PY_LITTLE_ENDIAN 0
+#else
+#define PY_BIG_ENDIAN 0
+#define PY_LITTLE_ENDIAN 1
+#endif
+
 #endif /* Py_PYPORT_H */
diff --git a/Misc/NEWS b/Misc/NEWS
index 5ee9729..d939a63 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@ What's New in Python 3.4.0 Alpha 1?
 Core and Builtins
 -----------------
 
+- Issue #16166: Add PY_LITTLE_ENDIAN and PY_BIG_ENDIAN macros and unified
+  endianess detection and handling.
+
 - Issue #15958: bytes.join and bytearray.join now accept arbitrary buffer
   objects.
 
diff --git a/Modules/_io/textio.c b/Modules/_io/textio.c
index 96434a8..8344d43 100644
--- a/Modules/_io/textio.c
+++ b/Modules/_io/textio.c
@@ -747,7 +747,7 @@ utf16_encode(textio *self, PyObject *text)
 {
     if (!self->encoding_start_of_stream) {
         /* Skip the BOM and use native byte ordering */
-#if defined(WORDS_BIGENDIAN)
+#if PY_BIG_ENDIAN
         return utf16be_encode(self, text);
 #else
         return utf16le_encode(self, text);
@@ -776,7 +776,7 @@ utf32_encode(textio *self, PyObject *text)
 {
     if (!self->encoding_start_of_stream) {
         /* Skip the BOM and use native byte ordering */
-#if defined(WORDS_BIGENDIAN)
+#if PY_BIG_ENDIAN
         return utf32be_encode(self, text);
 #else
         return utf32le_encode(self, text);
@@ -1913,10 +1913,7 @@ typedef struct {
 
 #define COOKIE_BUF_LEN      (sizeof(Py_off_t) + 3 * sizeof(int) + sizeof(char))
 
-#if defined(WORDS_BIGENDIAN)
-
-# define IS_LITTLE_ENDIAN   0
-
+#if PY_BIG_ENDIAN
 /* We want the least significant byte of start_pos to also be the least
    significant byte of the cookie, which means that in big-endian mode we
    must copy the fields in reverse order. */
@@ -1928,9 +1925,6 @@ typedef struct {
 # define OFF_NEED_EOF       0
 
 #else
-
-# define IS_LITTLE_ENDIAN   1
-
 /* Little-endian mode: the least significant byte of start_pos will
    naturally end up the least significant byte of the cookie. */
 
@@ -1951,7 +1945,7 @@ textiowrapper_parse_cookie(cookie_type *cookie, PyObject *cookieObj)
         return -1;
 
     if (_PyLong_AsByteArray(cookieLong, buffer, sizeof(buffer),
-                            IS_LITTLE_ENDIAN, 0) < 0) {
+                            PY_LITTLE_ENDIAN, 0) < 0) {
         Py_DECREF(cookieLong);
         return -1;
     }
@@ -1977,9 +1971,9 @@ textiowrapper_build_cookie(cookie_type *cookie)
     memcpy(buffer + OFF_CHARS_TO_SKIP, &cookie->chars_to_skip, sizeof(cookie->chars_to_skip));
     memcpy(buffer + OFF_NEED_EOF, &cookie->need_eof, sizeof(cookie->need_eof));
 
-    return _PyLong_FromByteArray(buffer, sizeof(buffer), IS_LITTLE_ENDIAN, 0);
+    return _PyLong_FromByteArray(buffer, sizeof(buffer),
+                                 PY_LITTLE_ENDIAN, 0);
 }
-#undef IS_LITTLE_ENDIAN
 
 static int
 _textiowrapper_decoder_setstate(textio *self, cookie_type *cookie)
diff --git a/Modules/_sha3/cleanup.py b/Modules/_sha3/cleanup.py
index 5238ab3..aabcb04 100755
--- a/Modules/_sha3/cleanup.py
+++ b/Modules/_sha3/cleanup.py
@@ -32,10 +32,10 @@ def cleanup(f):
         if line.startswith("typedef unsigned long long int"):
             buf.append("/* %s */\n" % line.strip())
             continue
-        ## remove #include "brg_endian.h"
-        #if "brg_endian.h" in line:
-        #    buf.append("/* %s */\n" % line.strip())
-        #    continue
+        # remove #include "brg_endian.h"
+        if "brg_endian.h" in line:
+            buf.append("/* %s */\n" % line.strip())
+            continue
         # transform C++ comments into ANSI C comments
         line = CPP1.sub(r"/* \1 */", line)
         line = CPP2.sub(r" /* \1 */", line)
diff --git a/Modules/_sha3/keccak/KeccakF-1600-opt32.c b/Modules/_sha3/keccak/KeccakF-1600-opt32.c
index 473dde5..dba6d59 100644
--- a/Modules/_sha3/keccak/KeccakF-1600-opt32.c
+++ b/Modules/_sha3/keccak/KeccakF-1600-opt32.c
@@ -12,7 +12,7 @@ http://creativecommons.org/publicdomain/zero/1.0/
 */
 
 #include <string.h>
-#include "brg_endian.h"
+/* #include "brg_endian.h" */
 #include "KeccakF-1600-opt32-settings.h"
 #include "KeccakF-1600-interface.h"
 
diff --git a/Modules/_sha3/keccak/KeccakF-1600-opt64.c b/Modules/_sha3/keccak/KeccakF-1600-opt64.c
index 57e2aa4..f19b18b 100644
--- a/Modules/_sha3/keccak/KeccakF-1600-opt64.c
+++ b/Modules/_sha3/keccak/KeccakF-1600-opt64.c
@@ -12,7 +12,7 @@ http://creativecommons.org/publicdomain/zero/1.0/
 */
 
 #include <string.h>
-#include "brg_endian.h"
+/* #include "brg_endian.h" */
 #include "KeccakF-1600-opt64-settings.h"
 #include "KeccakF-1600-interface.h"
 
diff --git a/Modules/_sha3/sha3module.c b/Modules/_sha3/sha3module.c
index 08f6839..4c3c6db 100644
--- a/Modules/_sha3/sha3module.c
+++ b/Modules/_sha3/sha3module.c
@@ -124,11 +124,14 @@
   #define UseInterleaveTables
 #endif
 
-/* replacement for brg_endian.h
-#define IS_BIG_ENDIAN BIG_ENDIAN
-#define IS_LITTLE_ENDIAN LITTLE_ENDIAN
-#define PLATFORM_BYTE_ORDER BYTE_ORDER
-*/
+/* replacement for brg_endian.h */
+#define IS_BIG_ENDIAN 4321
+#define IS_LITTLE_ENDIAN 1234
+#if PY_BIG_ENDIAN
+#  define PLATFORM_BYTE_ORDER IS_BIG_ENDIAN
+#else
+#  define PLATFORM_BYTE_ORDER IS_LITTLE_ENDIAN
+#endif
 
 /* inline all Keccak dependencies */
 #include "keccak/KeccakNISTInterface.h"
diff --git a/Modules/_struct.c b/Modules/_struct.c
index 0b20e26..0f50144 100644
--- a/Modules/_struct.c
+++ b/Modules/_struct.c
@@ -1199,12 +1199,11 @@ whichtable(char **pfmt)
     case '!': /* Network byte order is big-endian */
         return bigendian_table;
     case '=': { /* Host byte order -- different from native in alignment! */
-        int n = 1;
-        char *p = (char *) &n;
-        if (*p == 1)
-            return lilendian_table;
-        else
-            return bigendian_table;
+#if PY_LITTLE_ENDIAN
+        return lilendian_table;
+#else
+        return bigendian_table;
+#endif
     }
     default:
         --*pfmt; /* Back out of pointer increment */
@@ -2088,13 +2087,13 @@ PyInit__struct(void)
 
     /* Check endian and swap in faster functions */
     {
-        int one = 1;
         formatdef *native = native_table;
         formatdef *other, *ptr;
-        if ((int)*(unsigned char*)&one)
-            other = lilendian_table;
-        else
-            other = bigendian_table;
+#if PY_LITTLE_ENDIAN
+        other = lilendian_table;
+#else
+        other = bigendian_table;
+#endif
         /* Scan through the native table, find a matching
            entry in the endian table and swap in the
            native implementations whenever possible
diff --git a/Modules/arraymodule.c b/Modules/arraymodule.c
index 3f5aa8b..4d4c2ae 100644
--- a/Modules/arraymodule.c
+++ b/Modules/arraymodule.c
@@ -1664,11 +1664,8 @@ static const struct mformatdescr {
 static enum machine_format_code
 typecode_to_mformat_code(char typecode)
 {
-#ifdef WORDS_BIGENDIAN
-    const int is_big_endian = 1;
-#else
-    const int is_big_endian = 0;
-#endif
+    const int is_big_endian = PY_BIG_ENDIAN;
+
     size_t intsize;
     int is_signed;
 
diff --git a/Modules/sha256module.c b/Modules/sha256module.c
index 76d91af..4abd1cd 100644
--- a/Modules/sha256module.c
+++ b/Modules/sha256module.c
@@ -21,13 +21,6 @@
 #include "hashlib.h"
 
 
-/* Endianness testing and definitions */
-#define TestEndianness(variable) {int i=1; variable=PCT_BIG_ENDIAN;\
-        if (*((char*)&i)==1) variable=PCT_LITTLE_ENDIAN;}
-
-#define PCT_LITTLE_ENDIAN 1
-#define PCT_BIG_ENDIAN 0
-
 /* Some useful types */
 
 typedef unsigned char SHA_BYTE;
@@ -50,7 +43,6 @@ typedef struct {
     SHA_INT32 digest[8];                /* Message digest */
     SHA_INT32 count_lo, count_hi;       /* 64-bit bit count */
     SHA_BYTE data[SHA_BLOCKSIZE];       /* SHA data buffer */
-    int Endianness;
     int local;                          /* unprocessed amount in data */
     int digestsize;
 } SHAobject;
@@ -58,13 +50,11 @@ typedef struct {
 /* When run on a little-endian CPU we need to perform byte reversal on an
    array of longwords. */
 
-static void longReverse(SHA_INT32 *buffer, int byteCount, int Endianness)
+#if PY_LITTLE_ENDIAN
+static void longReverse(SHA_INT32 *buffer, int byteCount)
 {
     SHA_INT32 value;
 
-    if ( Endianness == PCT_BIG_ENDIAN )
-        return;
-
     byteCount /= sizeof(*buffer);
     while (byteCount--) {
         value = *buffer;
@@ -73,10 +63,10 @@ static void longReverse(SHA_INT32 *buffer, int byteCount, int Endianness)
         *buffer++ = ( value << 16 ) | ( value >> 16 );
     }
 }
+#endif
 
 static void SHAcopy(SHAobject *src, SHAobject *dest)
 {
-    dest->Endianness = src->Endianness;
     dest->local = src->local;
     dest->digestsize = src->digestsize;
     dest->count_lo = src->count_lo;
@@ -131,7 +121,9 @@ sha_transform(SHAobject *sha_info)
         SHA_INT32 S[8], W[64], t0, t1;
 
     memcpy(W, sha_info->data, sizeof(sha_info->data));
-    longReverse(W, (int)sizeof(sha_info->data), sha_info->Endianness);
+#if PY_LITTLE_ENDIAN
+    longReverse(W, (int)sizeof(sha_info->data));
+#endif
 
     for (i = 16; i < 64; ++i) {
                 W[i] = Gamma1(W[i - 2]) + W[i - 7] + Gamma0(W[i - 15]) + W[i - 16];
@@ -228,7 +220,6 @@ sha_transform(SHAobject *sha_info)
 static void
 sha_init(SHAobject *sha_info)
 {
-    TestEndianness(sha_info->Endianness)
     sha_info->digest[0] = 0x6A09E667L;
     sha_info->digest[1] = 0xBB67AE85L;
     sha_info->digest[2] = 0x3C6EF372L;
@@ -246,7 +237,6 @@ sha_init(SHAobject *sha_info)
 static void
 sha224_init(SHAobject *sha_info)
 {
-    TestEndianness(sha_info->Endianness)
     sha_info->digest[0] = 0xc1059ed8L;
     sha_info->digest[1] = 0x367cd507L;
     sha_info->digest[2] = 0x3070dd17L;
diff --git a/Modules/sha512module.c b/Modules/sha512module.c
index 88f8a64..bfb022c 100644
--- a/Modules/sha512module.c
+++ b/Modules/sha512module.c
@@ -22,13 +22,6 @@
 
 #ifdef PY_LONG_LONG /* If no PY_LONG_LONG, don't compile anything! */
 
-/* Endianness testing and definitions */
-#define TestEndianness(variable) {int i=1; variable=PCT_BIG_ENDIAN;\
-        if (*((char*)&i)==1) variable=PCT_LITTLE_ENDIAN;}
-
-#define PCT_LITTLE_ENDIAN 1
-#define PCT_BIG_ENDIAN 0
-
 /* Some useful types */
 
 typedef unsigned char SHA_BYTE;
@@ -52,7 +45,6 @@ typedef struct {
     SHA_INT64 digest[8];                /* Message digest */
     SHA_INT32 count_lo, count_hi;       /* 64-bit bit count */
     SHA_BYTE data[SHA_BLOCKSIZE];       /* SHA data buffer */
-    int Endianness;
     int local;                          /* unprocessed amount in data */
     int digestsize;
 } SHAobject;
@@ -60,13 +52,11 @@ typedef struct {
 /* When run on a little-endian CPU we need to perform byte reversal on an
    array of longwords. */
 
-static void longReverse(SHA_INT64 *buffer, int byteCount, int Endianness)
+#if PY_LITTLE_ENDIAN
+static void longReverse(SHA_INT64 *buffer, int byteCount)
 {
     SHA_INT64 value;
 
-    if ( Endianness == PCT_BIG_ENDIAN )
-        return;
-
     byteCount /= sizeof(*buffer);
     while (byteCount--) {
         value = *buffer;
@@ -83,10 +73,10 @@ static void longReverse(SHA_INT64 *buffer, int byteCount, int Endianness)
                 buffer++;
     }
 }
+#endif
 
 static void SHAcopy(SHAobject *src, SHAobject *dest)
 {
-    dest->Endianness = src->Endianness;
     dest->local = src->local;
     dest->digestsize = src->digestsize;
     dest->count_lo = src->count_lo;
@@ -141,7 +131,9 @@ sha512_transform(SHAobject *sha_info)
     SHA_INT64 S[8], W[80], t0, t1;
 
     memcpy(W, sha_info->data, sizeof(sha_info->data));
-    longReverse(W, (int)sizeof(sha_info->data), sha_info->Endianness);
+#if PY_LITTLE_ENDIAN
+    longReverse(W, (int)sizeof(sha_info->data));
+#endif
 
     for (i = 16; i < 80; ++i) {
                 W[i] = Gamma1(W[i - 2]) + W[i - 7] + Gamma0(W[i - 15]) + W[i - 16];
@@ -254,7 +246,6 @@ sha512_transform(SHAobject *sha_info)
 static void
 sha512_init(SHAobject *sha_info)
 {
-    TestEndianness(sha_info->Endianness)
     sha_info->digest[0] = Py_ULL(0x6a09e667f3bcc908);
     sha_info->digest[1] = Py_ULL(0xbb67ae8584caa73b);
     sha_info->digest[2] = Py_ULL(0x3c6ef372fe94f82b);
@@ -272,7 +263,6 @@ sha512_init(SHAobject *sha_info)
 static void
 sha384_init(SHAobject *sha_info)
 {
-    TestEndianness(sha_info->Endianness)
     sha_info->digest[0] = Py_ULL(0xcbbb9d5dc1059ed8);
     sha_info->digest[1] = Py_ULL(0x629a292a367cd507);
     sha_info->digest[2] = Py_ULL(0x9159015a3070dd17);
diff --git a/Objects/longobject.c b/Objects/longobject.c
index 2aac8e4..ead4680 100644
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -988,7 +988,6 @@ PyLong_AsVoidPtr(PyObject *vv)
  * rewritten to use the newer PyLong_{As,From}ByteArray API.
  */
 
-#define IS_LITTLE_ENDIAN (int)*(unsigned char*)&one
 #define PY_ABS_LLONG_MIN (0-(unsigned PY_LONG_LONG)PY_LLONG_MIN)
 
 /* Create a new long int object from a C PY_LONG_LONG int. */
@@ -1141,7 +1140,6 @@ PyLong_AsLongLong(PyObject *vv)
 {
     PyLongObject *v;
     PY_LONG_LONG bytes;
-    int one = 1;
     int res;
 
     if (vv == NULL) {
@@ -1176,7 +1174,7 @@ PyLong_AsLongLong(PyObject *vv)
     case 1: return v->ob_digit[0];
     }
     res = _PyLong_AsByteArray((PyLongObject *)vv, (unsigned char *)&bytes,
-                              SIZEOF_LONG_LONG, IS_LITTLE_ENDIAN, 1);
+                              SIZEOF_LONG_LONG, PY_LITTLE_ENDIAN, 1);
 
     /* Plan 9 can't handle PY_LONG_LONG in ? : expressions */
     if (res < 0)
@@ -1193,7 +1191,6 @@ PyLong_AsUnsignedLongLong(PyObject *vv)
 {
     PyLongObject *v;
     unsigned PY_LONG_LONG bytes;
-    int one = 1;
     int res;
 
     if (vv == NULL) {
@@ -1212,7 +1209,7 @@ PyLong_AsUnsignedLongLong(PyObject *vv)
     }
 
     res = _PyLong_AsByteArray((PyLongObject *)vv, (unsigned char *)&bytes,
-                              SIZEOF_LONG_LONG, IS_LITTLE_ENDIAN, 0);
+                              SIZEOF_LONG_LONG, PY_LITTLE_ENDIAN, 0);
 
     /* Plan 9 can't handle PY_LONG_LONG in ? : expressions */
     if (res < 0)
@@ -1288,7 +1285,6 @@ PyLong_AsUnsignedLongLongMask(register PyObject *op)
         return (unsigned PY_LONG_LONG)-1;
     }
 }
-#undef IS_LITTLE_ENDIAN
 
 /* Get a C long long int from a long int object or any object that has an
    __int__ method.
diff --git a/Objects/stringlib/codecs.h b/Objects/stringlib/codecs.h
index 2a01089..cbf3508 100644
--- a/Objects/stringlib/codecs.h
+++ b/Objects/stringlib/codecs.h
@@ -47,7 +47,7 @@ STRINGLIB(utf8_decode)(const char **inptr, const char *end,
                     unsigned long value = *(unsigned long *) _s;
                     if (value & ASCII_CHAR_MASK)
                         break;
-#ifdef BYTEORDER_IS_LITTLE_ENDIAN
+#if PY_LITTLE_ENDIAN
                     _p[0] = (STRINGLIB_CHAR)(value & 0xFFu);
                     _p[1] = (STRINGLIB_CHAR)((value >> 8) & 0xFFu);
                     _p[2] = (STRINGLIB_CHAR)((value >> 16) & 0xFFu);
@@ -454,7 +454,7 @@ STRINGLIB(utf16_decode)(const unsigned char **inptr, const unsigned char *e,
     const unsigned char *q = *inptr;
     STRINGLIB_CHAR *p = dest + *outpos;
     /* Offsets from q for retrieving byte pairs in the right order. */
-#ifdef BYTEORDER_IS_LITTLE_ENDIAN
+#if PY_LITTLE_ENDIAN
     int ihi = !!native_ordering, ilo = !native_ordering;
 #else
     int ihi = !native_ordering, ilo = !!native_ordering;
@@ -485,7 +485,7 @@ STRINGLIB(utf16_decode)(const unsigned char **inptr, const unsigned char *e,
                     block = SWAB(block);
 #endif
                 }
-#ifdef BYTEORDER_IS_LITTLE_ENDIAN
+#if PY_LITTLE_ENDIAN
 # if SIZEOF_LONG == 4
                 p[0] = (STRINGLIB_CHAR)(block & 0xFFFFu);
                 p[1] = (STRINGLIB_CHAR)(block >> 16);
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index b4c7ecf..9461563 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -47,14 +47,6 @@ OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 #include <windows.h>
 #endif
 
-/* Endianness switches; defaults to little endian */
-
-#ifdef WORDS_BIGENDIAN
-# define BYTEORDER_IS_BIG_ENDIAN
-#else
-# define BYTEORDER_IS_LITTLE_ENDIAN
-#endif
-
 /* --- Globals ------------------------------------------------------------
 
    The globals are initialized by the _PyUnicode_Init() API and should
@@ -4813,7 +4805,7 @@ PyUnicode_DecodeUTF32Stateful(const char *s,
     int bo = 0;       /* assume native ordering by default */
     const char *errmsg = "";
     /* Offsets from q for retrieving bytes in the right order. */
-#ifdef BYTEORDER_IS_LITTLE_ENDIAN
+#if PY_LITTLE_ENDIAN
     int iorder[] = {0, 1, 2, 3};
 #else
     int iorder[] = {3, 2, 1, 0};
@@ -4835,7 +4827,7 @@ PyUnicode_DecodeUTF32Stateful(const char *s,
         if (size >= 4) {
             const Py_UCS4 bom = (q[iorder[3]] << 24) | (q[iorder[2]] << 16) |
                 (q[iorder[1]] << 8) | q[iorder[0]];
-#ifdef BYTEORDER_IS_LITTLE_ENDIAN
+#if PY_LITTLE_ENDIAN
             if (bom == 0x0000FEFF) {
                 q += 4;
                 bo = -1;
@@ -4949,7 +4941,7 @@ _PyUnicode_EncodeUTF32(PyObject *str,
     unsigned char *p;
     Py_ssize_t nsize, i;
     /* Offsets from p for storing byte pairs in the right order. */
-#ifdef BYTEORDER_IS_LITTLE_ENDIAN
+#if PY_LITTLE_ENDIAN
     int iorder[] = {0, 1, 2, 3};
 #else
     int iorder[] = {3, 2, 1, 0};
@@ -5092,7 +5084,7 @@ PyUnicode_DecodeUTF16Stateful(const char *s,
         return unicode_empty;
     }
 
-#ifdef BYTEORDER_IS_LITTLE_ENDIAN
+#if PY_LITTLE_ENDIAN
     native_ordering = bo <= 0;
 #else
     native_ordering = bo >= 0;
@@ -5209,7 +5201,7 @@ _PyUnicode_EncodeUTF16(PyObject *str,
     unsigned short *out;
     Py_ssize_t bytesize;
     Py_ssize_t pairs;
-#ifdef WORDS_BIGENDIAN
+#if PY_BIG_ENDIAN
     int native_ordering = byteorder >= 0;
 #else
     int native_ordering = byteorder <= 0;
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 20bfa55..cafbb58 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -1561,7 +1561,6 @@ PyObject *
 _PySys_Init(void)
 {
     PyObject *m, *v, *sysdict, *version_info;
-    char *s;
 
     m = PyModule_Create(&sysmodule);
     if (m == NULL)
@@ -1638,20 +1637,14 @@ _PySys_Init(void)
                         PyLong_FromLong(0x10FFFF));
     SET_SYS_FROM_STRING("builtin_module_names",
                         list_builtin_module_names());
-    {
-        /* Assumes that longs are at least 2 bytes long.
-           Should be safe! */
-        unsigned long number = 1;
-        char *value;
-
-        s = (char *) &number;
-        if (s[0] == 0)
-            value = "big";
-        else
-            value = "little";
-        SET_SYS_FROM_STRING("byteorder",
-                            PyUnicode_FromString(value));
-    }
+#if PY_BIG_ENDIAN
+    SET_SYS_FROM_STRING("byteorder",
+                        PyUnicode_FromString("big"));
+#else
+    SET_SYS_FROM_STRING("byteorder",
+                        PyUnicode_FromString("little"));
+#endif
+
 #ifdef MS_COREDLL
     SET_SYS_FROM_STRING("dllhandle",
                         PyLong_FromVoidPtr(PyWin_DLLhModule));