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7d3a511a40
This was a convenient excuse to create the pyport.h file recently discussed! Please use new Py_ARITHMETIC_RIGHT_SHIFT when right-shifting a signed int and you *need* sign-extension. This is #define'd in pyport.h, keying off new config symbol SIGNED_RIGHT_SHIFT_ZERO_FILLS. If you're running on a platform that needs that symbol #define'd, the std tests never would have worked for you (in particular, at least test_long would have failed). The autoconfig stuff got added to Python after my Unix days, so I don't know how that works. Would someone please look into doing & testing an auto-config of the SIGNED_RIGHT_SHIFT_ZERO_FILLS symbol? It needs to be defined if & only if, e.g., (-1) >> 3 is not -1.
58 lines
1.9 KiB
C
58 lines
1.9 KiB
C
/***********************************************************
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Copyright (c) 2000, BeOpen.com.
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All rights reserved.
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See the file "Misc/COPYRIGHT" for information on usage and
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redistribution of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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******************************************************************/
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#ifndef Py_PYPORT_H
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#define Py_PYPORT_H 1
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/**************************************************************************
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Symbols and macros to supply platform-independent interfaces to basic
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C-language operations whose spellings vary across platforms.
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Please try to make documentation here as clear as possible: by definition,
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the stuff here is trying to illuminate C's darkest corners.
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Config #defines referenced here:
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SIGNED_RIGHT_SHIFT_ZERO_FILLS
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Meaning: To be defined iff i>>j does not extend the sign bit when i is a
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signed integral type and i < 0.
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Used in: Py_ARITHMETIC_RIGHT_SHIFT
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**************************************************************************/
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* Py_ARITHMETIC_RIGHT_SHIFT
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* C doesn't define whether a right-shift of a signed integer sign-extends
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* or zero-fills. Here a macro to force sign extension:
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* Py_ARITHMETIC_RIGHT_SHIFT(TYPE, I, J)
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* Return I >> J, forcing sign extension.
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* Requirements:
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* I is of basic signed type TYPE (char, short, int, long, or long long).
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* TYPE is one of char, short, int, long, or long long, although long long
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* must not be used except on platforms that support it.
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* J is an integer >= 0 and strictly less than the number of bits in TYPE
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* (because C doesn't define what happens for J outside that range either).
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* Caution:
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* I may be evaluated more than once.
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*/
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#ifdef SIGNED_RIGHT_SHIFT_ZERO_FILLS
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#define Py_ARITHMETIC_RIGHT_SHIFT(TYPE, I, J) \
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((I) < 0 ? ~((~(unsigned TYPE)(I)) >> (J)) : (I) >> (J))
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#else
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#define Py_ARITHMETIC_RIGHT_SHIFT(TYPE, I, J) ((I) >> (J))
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#endif
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#ifdef __cplusplus
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}
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#endif
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#endif /* Py_PYPORT_H */
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