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py/mpconfig.h: Be stricter when autodetecting machine endianness. 

This patch changes 2 things in the endianness detection:

1. Don't assume that __BYTE_ORDER__ not being __ORDER_LITTLE_ENDIAN__ means
   that the machine is big endian, so add an explicit check that this macro
   is indeed __ORDER_BIG_ENDIAN__ (same with __BYTE_ORDER, __LITTLE_ENDIAN
   and __BIG_ENDIAN).  A machine could have PDP endianness.

2. Remove the checks which base their autodetection decision on whether any
   little or big endian macros are defined (eg __LITTLE_ENDIAN__ or
   __BIG_ENDIAN__).  Just because a system defines these does not mean it
   has that endianness.

See issue #3760.
This commit is contained in:
Damien George 2018-05-07 13:36:52 +10:00
parent 7541be5637
commit 9630376dbc
1 changed files with 6 additions and 9 deletions
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15
py/mpconfig.h
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@ -1256,29 +1256,26 @@ typedef double mp_float_t;
#elif defined(MP_ENDIANNESS_BIG)
#define MP_ENDIANNESS_LITTLE (!MP_ENDIANNESS_BIG)
#else
// Endiannes not defined by port so try to autodetect it.
// Endianness not defined by port so try to autodetect it.
#if defined(__BYTE_ORDER__)
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
#define MP_ENDIANNESS_LITTLE (1)
#else
#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
#define MP_ENDIANNESS_LITTLE (0)
#endif
#elif defined(__LITTLE_ENDIAN__) || defined(__LITTLE_ENDIAN) || defined (_LITTLE_ENDIAN)
#define MP_ENDIANNESS_LITTLE (1)
#elif defined(__BIG_ENDIAN__) || defined(__BIG_ENDIAN) || defined (_BIG_ENDIAN)
#define MP_ENDIANNESS_LITTLE (0)
#else
#include <endian.h>
#if defined(__BYTE_ORDER)
#if __BYTE_ORDER == __LITTLE_ENDIAN
#define MP_ENDIANNESS_LITTLE (1)
#else
#elif __BYTE_ORDER == __BIG_ENDIAN
#define MP_ENDIANNESS_LITTLE (0)
#endif
#else
#error endianness not defined and cannot detect it
#endif
#endif
#ifndef MP_ENDIANNESS_LITTLE
#error endianness not defined and cannot detect it
#endif
#define MP_ENDIANNESS_BIG (!MP_ENDIANNESS_LITTLE)
#endif