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| author | Mark Dickinson <dickinsm@gmail.com> | 2009-01-26 21:43:42 (GMT) |
|---|---|---|
| committer | Mark Dickinson <dickinsm@gmail.com> | 2009-01-26 21:43:42 (GMT) |
| commit | 24058549f59dcad3d11b04430366d7dbfdcfe27a (patch) | |
| tree | 11bd05b4f999aeb384812f17bdfc3220bced880e /Objects | |
| parent | f66326f8bd182659a31f3e762efb47cdfd24b588 (diff) | |
| download | cpython-24058549f59dcad3d11b04430366d7dbfdcfe27a.zip cpython-24058549f59dcad3d11b04430366d7dbfdcfe27a.tar.gz cpython-24058549f59dcad3d11b04430366d7dbfdcfe27a.tar.bz2 | |
Merged revisions 68974-68975 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk
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r68974 | mark.dickinson | 2009-01-26 21:36:30 +0000 (Mon, 26 Jan 2009) | 4 lines
Fix undefined behaviour (left shift of negative value) in long_hash. Also,
rewrap a line of length > 79, and update comments.
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r68975 | mark.dickinson | 2009-01-26 21:40:08 +0000 (Mon, 26 Jan 2009) | 2 lines
Fix comment.
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Diffstat (limited to 'Objects')
| -rw-r--r-- | Objects/longobject.c | 17 |
1 files changed, 9 insertions, 8 deletions
diff --git a/Objects/longobject.c b/Objects/longobject.c index f19425d..d49752f 100644 --- a/Objects/longobject.c +++ b/Objects/longobject.c @@ -1962,7 +1962,7 @@ long_compare(PyLongObject *a, PyLongObject *b) static long long_hash(PyLongObject *v) { - long x; + unsigned long x; Py_ssize_t i; int sign; @@ -1977,17 +1977,18 @@ long_hash(PyLongObject *v) i = -(i); } #define LONG_BIT_PyLong_SHIFT (8*sizeof(long) - PyLong_SHIFT) - /* The following loop produces a C long x such that (unsigned long)x - is congruent to the absolute value of v modulo ULONG_MAX. The + /* The following loop produces a C unsigned long x such that x is + congruent to the absolute value of v modulo ULONG_MAX. The resulting x is nonzero if and only if v is. */ while (--i >= 0) { /* Force a native long #-bits (32 or 64) circular shift */ - x = ((x << PyLong_SHIFT) & ~PyLong_MASK) | ((x >> LONG_BIT_PyLong_SHIFT) & PyLong_MASK); + x = ((x << PyLong_SHIFT) & ~PyLong_MASK) | + ((x >> LONG_BIT_PyLong_SHIFT) & PyLong_MASK); x += v->ob_digit[i]; - /* If the addition above overflowed (thinking of x as - unsigned), we compensate by incrementing. This preserves - the value modulo ULONG_MAX. */ - if ((unsigned long)x < v->ob_digit[i]) + /* If the addition above overflowed we compensate by + incrementing. This preserves the value modulo + ULONG_MAX. */ + if (x < v->ob_digit[i]) x++; } #undef LONG_BIT_PyLong_SHIFT |