[issue22012] struct.unpack('?', '\x02') returns (False,) on Mac OSX

[Ned Deily]

Ned Deily added the comment:

Doing a quick look, the results vary.  Using current python.org 2.7.8 and 3.4.1 installers, the results are correct.  These interpreters are built with Apple gcc-4.2 (non-LLVM) from Xcode 3.2.6.  Other 2.7 and 3.4.x builds I have available at the moment, including the Apple-supplied Python 2.7, were built with clang LLVM and they all give the incorrect result.
  
$ /usr/bin/python2.7 -c "import sys,struct;print(struct.unpack('????', b'\x00\x01\x02\x03'), sys.version)"
((False, True, False, True), '2.7.5 (default, Mar  9 2014, 22:15:05) \n[GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.0.68)]')

$ arch -i386 /usr/bin/python2.7 -c "import sys,struct;print(struct.unpack('????', b'\x00\x01\x02\x03'), sys.version)"
((False, True, False, True), '2.7.5 (default, Mar  9 2014, 22:15:05) \n[GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.0.68)]')

$ /usr/local/bin/python2.7 -c "import sys,struct;print(struct.unpack('????', b'\x00\x01\x02\x03'), sys.version)"
((False, True, True, True), '2.7.8 (v2.7.8:ee879c0ffa11, Jun 29 2014, 21:07:35) \n[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)]')

$ /usr/local/bin/python2.7-32 -c "import sys,struct;print(struct.unpack('????', b'\x00\x01\x02\x03'), sys.version)"
((False, True, True, True), '2.7.8 (v2.7.8:ee879c0ffa11, Jun 29 2014, 21:07:35) \n[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)]')

$ /usr/local/bin/python3.4 -c "import sys,struct;print(struct.unpack('????', b'\x00\x01\x02\x03'), sys.version)"
(False, True, True, True) 3.4.1 (v3.4.1:c0e311e010fc, May 18 2014, 00:54:21)
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)]

$ /usr/local/bin/python3.4-32 -c "import sys,struct;print(struct.unpack('????', b'\x00\x01\x02\x03'), sys.version)"
(False, True, True, True) 3.4.1 (v3.4.1:c0e311e010fc, May 18 2014, 00:54:21)
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)]

$ ./bin/python3.4 -c "import sys,struct;print(struct.unpack('????', b'\x00\x01\x02\x03'), sys.version)"
(False, True, False, True) 3.4.1+ (3.4:d6b71971b228, Jul 16 2014, 16:30:56)
[GCC 4.2.1 Compatible Apple LLVM 5.1 (clang-503.0.40)]

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nosy: +ned.deily
versions:  -Python 3.1, Python 3.2, Python 3.3

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<http://bugs.python.org/issue22012>
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