big endian detection fails on stock Apple compilers (gcc 4.2 and less) on PPC

[kencu]

I noticed that on some older PPC systems I have, the SHA1 hashes created in git were failing since this code was included. When built with newer gcc compilers (e.g. gcc6) git would generate properly working binaries.

The stock Apple compilers are gcc-4.2 and less, and they don't generate the #defines needed to succeed in the current big endian tests. Forcing big endian with -DSHA1DC_FORCE_BIGENDIAN does work to create a working git.

Perhaps the big endian detection might be tweaked to add support for these older stock Apple compilers, and that would fix git on these systems.

Here's the output:

$ ./gcc-apple-4.2 -E -dM  - < /dev/null
#define __DBL_MIN_EXP__ (-1021)
#define __FLT_MIN__ 1.17549435e-38F
#define __DEC64_DEN__ 0.000000000000001E-383DD
#define __CHAR_BIT__ 8
#define _ARCH_PPCGR 1
#define __WCHAR_MAX__ 2147483647
#define __DBL_DENORM_MIN__ 4.9406564584124654e-324
#define __FLT_EVAL_METHOD__ 0
#define __DBL_MIN_10_EXP__ (-307)
#define __FINITE_MATH_ONLY__ 0
#define __GNUC_PATCHLEVEL__ 1
#define __DEC64_MAX_EXP__ 384
#define __SHRT_MAX__ 32767
#define __LDBL_MAX__ 1.79769313486231580793728971405301e+308L
#define __APPLE_CC__ 5666
#define __UINTMAX_TYPE__ long long unsigned int
#define __DEC32_EPSILON__ 1E-6DF
#define __block __attribute__((__blocks__(byref)))
#define __LDBL_MAX_EXP__ 1024
#define __SCHAR_MAX__ 127
#define __USER_LABEL_PREFIX__ _
#define __STDC_HOSTED__ 1
#define __LDBL_HAS_INFINITY__ 1
#define __DEC64_MIN_EXP__ (-383)
#define __DBL_DIG__ 15
#define __FLT_EPSILON__ 1.19209290e-7F
#define __LDBL_MIN__ 2.00416836000897277799610805135016e-292L
#define __DEC32_MAX__ 9.999999E96DF
#define __ppc__ 1
#define __strong 
#define __APPLE__ 1
#define __DECIMAL_DIG__ 33
#define __LDBL_HAS_QUIET_NAN__ 1
#define __DYNAMIC__ 1
#define __GNUC__ 4
#define __FLT_HAS_DENORM__ 1
#define __DBL_MAX__ 1.7976931348623157e+308
#define __DBL_HAS_INFINITY__ 1
#define __DEC32_MIN_EXP__ (-95)
#define OBJC_NEW_PROPERTIES 1
#define __LDBL_HAS_DENORM__ 1
#define __DEC128_MAX__ 9.999999999999999999999999999999999E6144DL
#define __DEC32_MIN__ 1E-95DF
#define __weak __attribute__((objc_gc(weak)))
#define __DBL_MAX_EXP__ 1024
#define __DEC128_EPSILON__ 1E-33DL
#define __LONG_LONG_MAX__ 9223372036854775807LL
#define __GXX_ABI_VERSION 1002
#define __FLT_MIN_EXP__ (-125)
#define __DBL_MIN__ 2.2250738585072014e-308
#define __DBL_HAS_QUIET_NAN__ 1
#define __DEC128_MIN__ 1E-6143DL
#define __REGISTER_PREFIX__ 
#define __DBL_HAS_DENORM__ 1
#define __NO_INLINE__ 1
#define __DEC_EVAL_METHOD__ 2
#define _ARCH_PPC 1
#define __FLT_MANT_DIG__ 24
#define __VERSION__ "4.2.1 (Apple Inc. build 5666) (dot 3) (MacPorts apple-gcc42 5666.3_15)"
#define __BIG_ENDIAN__ 1
#define __DEC64_EPSILON__ 1E-15DD
#define __DEC128_MIN_EXP__ (-6143)
#define __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ 1040
#define __SIZE_TYPE__ long unsigned int
#define __DEC32_DEN__ 0.000001E-95DF
#define __FLT_RADIX__ 2
#define __LDBL_EPSILON__ 4.94065645841246544176568792868221e-324L
#define __NATURAL_ALIGNMENT__ 1
#define __LDBL_DIG__ 31
#define __FLT_HAS_QUIET_NAN__ 1
#define __FLT_MAX_10_EXP__ 38
#define __LONG_MAX__ 2147483647L
#define __FLT_HAS_INFINITY__ 1
#define __DEC64_MAX__ 9.999999999999999E384DD
#define __DEC64_MANT_DIG__ 16
#define __DEC32_MAX_EXP__ 96
#define _BIG_ENDIAN 1
#define __DEC128_DEN__ 0.000000000000000000000000000000001E-6143DL
#define __LDBL_MANT_DIG__ 106
#define __CONSTANT_CFSTRINGS__ 1
#define __WCHAR_TYPE__ int
#define __pic__ 2
#define __FLT_DIG__ 6
#define __INT_MAX__ 2147483647
#define __LONG_DOUBLE_128__ 1
#define __FLT_MAX_EXP__ 128
#define __BLOCKS__ 1
#define __DBL_MANT_DIG__ 53
#define __DEC64_MIN__ 1E-383DD
#define __WINT_TYPE__ int
#define __LDBL_MIN_EXP__ (-968)
#define __MACH__ 1
#define __LDBL_MAX_10_EXP__ 308
#define __DBL_EPSILON__ 2.2204460492503131e-16
#define __INTMAX_MAX__ 9223372036854775807LL
#define __FLT_DENORM_MIN__ 1.40129846e-45F
#define __PIC__ 2
#define __FLT_MAX__ 3.40282347e+38F
#define __FLT_MIN_10_EXP__ (-37)
#define __INTMAX_TYPE__ long long int
#define __DEC128_MAX_EXP__ 6144
#define __GNUC_MINOR__ 2
#define __DEC32_MANT_DIG__ 7
#define __DBL_MAX_10_EXP__ 308
#define __LDBL_DENORM_MIN__ 4.94065645841246544176568792868221e-324L
#define __STDC__ 1
#define __PTRDIFF_TYPE__ int
#define __DEC128_MANT_DIG__ 34
#define __LDBL_MIN_10_EXP__ (-291)
#define __POWERPC__ 1
#define __GNUC_GNU_INLINE__ 1

perhaps checking for __APPLE__ and __BIG_ENDIAN__ would do it?

[kencu]

See also https://trac.macports.org/ticket/54602 for the ticket this was worked on.

[kencu]

https://github.com/kencu/macports-ports/blob/0261b9a80b537020f07b58831c2b5eb44404a27a/devel/git/files/patch-sha1dc-older-apple-gcc-versions.diff