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authorMark Dickinson <dickinsm@gmail.com>2009-03-20 23:23:15 (GMT)
committerMark Dickinson <dickinsm@gmail.com>2009-03-20 23:23:15 (GMT)
commit16f966ee2618f7a6604b94de2e478637676f550e (patch)
treed5485383f759cbf9952847c04a5f09f1b0cb2c1a /Include
parentbe075b1c4ed96d3b7550833a9a558690c2e6c0f9 (diff)
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Merged revisions 70489 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk ........ r70489 | mark.dickinson | 2009-03-20 23:16:14 +0000 (Fri, 20 Mar 2009) | 4 lines Rewrite Py_ARITHMETIC_RIGHT_SHIFT so that it's valid for all signed integer types T, not just those for which "unsigned T" is legal. ........
Diffstat (limited to 'Include')
-rw-r--r--Include/pyport.h18
1 files changed, 11 insertions, 7 deletions
diff --git a/Include/pyport.h b/Include/pyport.h
index 9449b5f..bf75d89 100644
--- a/Include/pyport.h
+++ b/Include/pyport.h
@@ -361,19 +361,23 @@ extern "C" {
* C doesn't define whether a right-shift of a signed integer sign-extends
* or zero-fills. Here a macro to force sign extension:
* Py_ARITHMETIC_RIGHT_SHIFT(TYPE, I, J)
- * Return I >> J, forcing sign extension.
+ * Return I >> J, forcing sign extension. Arithmetically, return the
+ * floor of I/2**J.
* Requirements:
- * I is of basic signed type TYPE (char, short, int, long, or long long).
- * TYPE is one of char, short, int, long, or long long, although long long
- * must not be used except on platforms that support it.
- * J is an integer >= 0 and strictly less than the number of bits in TYPE
- * (because C doesn't define what happens for J outside that range either).
+ * I should have signed integer type. In the terminology of C99, this can
+ * be either one of the five standard signed integer types (signed char,
+ * short, int, long, long long) or an extended signed integer type.
+ * J is an integer >= 0 and strictly less than the number of bits in the
+ * type of I (because C doesn't define what happens for J outside that
+ * range either).
+ * TYPE used to specify the type of I, but is now ignored. It's been left
+ * in for backwards compatibility with versions <= 2.6 or 3.0.
* Caution:
* I may be evaluated more than once.
*/
#ifdef SIGNED_RIGHT_SHIFT_ZERO_FILLS
#define Py_ARITHMETIC_RIGHT_SHIFT(TYPE, I, J) \
- ((I) < 0 ? ~((~(unsigned TYPE)(I)) >> (J)) : (I) >> (J))
+ ((I) < 0 ? -1-((-1-(I)) >> (J)) : (I) >> (J))
#else
#define Py_ARITHMETIC_RIGHT_SHIFT(TYPE, I, J) ((I) >> (J))
#endif