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| author | Mark Dickinson <mdickinson@enthought.com> | 2021-08-20 10:40:11 (GMT) |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2021-08-20 10:40:11 (GMT) |
| commit | 60b93d9e4922eeae25052bc15909d1f4152babde (patch) | |
| tree | cc4b4b829ba5a2e8a5a4d8b97b99bea473d8f58c | |
| parent | d26dbba9297adb59bc49a6583c647804ef56fc58 (diff) | |
| download | cpython-60b93d9e4922eeae25052bc15909d1f4152babde.zip cpython-60b93d9e4922eeae25052bc15909d1f4152babde.tar.gz cpython-60b93d9e4922eeae25052bc15909d1f4152babde.tar.bz2 | |
bpo-44954: Fix wrong result in float.fromhex corner case (GH-27834)
| -rw-r--r-- | Lib/test/test_float.py | 14 | ||||
| -rw-r--r-- | Misc/NEWS.d/next/Core and Builtins/2021-08-19-14-43-24.bpo-44954.dLn3lg.rst | 2 | ||||
| -rw-r--r-- | Objects/floatobject.c | 4 |
3 files changed, 18 insertions, 2 deletions
diff --git a/Lib/test/test_float.py b/Lib/test/test_float.py index 38a17ce..29f7756 100644 --- a/Lib/test/test_float.py +++ b/Lib/test/test_float.py @@ -1468,6 +1468,20 @@ class HexFloatTestCase(unittest.TestCase): self.identical(fromHex('0X1.0000000000001fp0'), 1.0+2*EPS) self.identical(fromHex('0x1.00000000000020p0'), 1.0+2*EPS) + # Regression test for a corner-case bug reported in b.p.o. 44954 + self.identical(fromHex('0x.8p-1074'), 0.0) + self.identical(fromHex('0x.80p-1074'), 0.0) + self.identical(fromHex('0x.81p-1074'), TINY) + self.identical(fromHex('0x8p-1078'), 0.0) + self.identical(fromHex('0x8.0p-1078'), 0.0) + self.identical(fromHex('0x8.1p-1078'), TINY) + self.identical(fromHex('0x80p-1082'), 0.0) + self.identical(fromHex('0x81p-1082'), TINY) + self.identical(fromHex('.8p-1074'), 0.0) + self.identical(fromHex('8p-1078'), 0.0) + self.identical(fromHex('-.8p-1074'), -0.0) + self.identical(fromHex('+8p-1078'), 0.0) + def test_roundtrip(self): def roundtrip(x): return fromHex(toHex(x)) diff --git a/Misc/NEWS.d/next/Core and Builtins/2021-08-19-14-43-24.bpo-44954.dLn3lg.rst b/Misc/NEWS.d/next/Core and Builtins/2021-08-19-14-43-24.bpo-44954.dLn3lg.rst new file mode 100644 index 0000000..4cdeb34 --- /dev/null +++ b/Misc/NEWS.d/next/Core and Builtins/2021-08-19-14-43-24.bpo-44954.dLn3lg.rst @@ -0,0 +1,2 @@ +Fixed a corner case bug where the result of ``float.fromhex('0x.8p-1074')`` +was rounded the wrong way. diff --git a/Objects/floatobject.c b/Objects/floatobject.c index 7e78132..92faa7c 100644 --- a/Objects/floatobject.c +++ b/Objects/floatobject.c @@ -1463,8 +1463,8 @@ float_fromhex(PyTypeObject *type, PyObject *string) bits lsb, lsb-2, lsb-3, lsb-4, ... is 1. */ if ((digit & half_eps) != 0) { round_up = 0; - if ((digit & (3*half_eps-1)) != 0 || - (half_eps == 8 && (HEX_DIGIT(key_digit+1) & 1) != 0)) + if ((digit & (3*half_eps-1)) != 0 || (half_eps == 8 && + key_digit+1 < ndigits && (HEX_DIGIT(key_digit+1) & 1) != 0)) round_up = 1; else for (i = key_digit-1; i >= 0; i--) |