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[3.14] gh-141042: fix sNaN's packing for mixed floating-point formats (GH-141107) (#141459)

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gh-141042: fix sNaN's packing for mixed floating-point formats (GH-141107)
(cherry picked from commit 23d85a2a3f)

Co-authored-by: Sergey B Kirpichev <skirpichev@gmail.com>
This commit is contained in:
Miss Islington (bot) 2025-11-12 11:33:34 +01:00 • committed by GitHub
parent 75b5157e84
commit e9c11b7495
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GPG key ID: B5690EEEBB952194
3 changed files with 59 additions and 14 deletions
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54
Lib/test/test_capi/test_float.py
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@ -29,6 +29,23 @@
NAN = float("nan")
def make_nan(size, sign, quiet, payload=None):
if size == 8:
payload_mask = 0x7ffffffffffff
i = (sign << 63) + (0x7ff << 52) + (quiet << 51)
elif size == 4:
payload_mask = 0x3fffff
i = (sign << 31) + (0xff << 23) + (quiet << 22)
elif size == 2:
payload_mask = 0x1ff
i = (sign << 15) + (0x1f << 10) + (quiet << 9)
else:
raise ValueError("size must be either 2, 4, or 8")
if payload is None:
payload = random.randint(not quiet, payload_mask)
return i + payload
class CAPIFloatTest(unittest.TestCase):
def test_check(self):
# Test PyFloat_Check()
@ -202,16 +219,7 @@ def test_pack_unpack_roundtrip_for_nans(self):
# HP PA RISC uses 0 for quiet, see:
# https://en.wikipedia.org/wiki/NaN#Encoding
signaling = 1
quiet = int(not signaling)
if size == 8:
payload = random.randint(signaling, 0x7ffffffffffff)
i = (sign << 63) + (0x7ff << 52) + (quiet << 51) + payload
elif size == 4:
payload = random.randint(signaling, 0x3fffff)
i = (sign << 31) + (0xff << 23) + (quiet << 22) + payload
elif size == 2:
payload = random.randint(signaling, 0x1ff)
i = (sign << 15) + (0x1f << 10) + (quiet << 9) + payload
i = make_nan(size, sign, not signaling)
data = bytes.fromhex(f'{i:x}')
for endian in (BIG_ENDIAN, LITTLE_ENDIAN):
with self.subTest(data=data, size=size, endian=endian):
@ -221,6 +229,32 @@ def test_pack_unpack_roundtrip_for_nans(self):
self.assertTrue(math.isnan(value))
self.assertEqual(data1, data2)
@unittest.skipUnless(HAVE_IEEE_754, "requires IEEE 754")
@unittest.skipUnless(sys.maxsize != 2147483647, "requires 64-bit mode")
def test_pack_unpack_nans_for_different_formats(self):
pack = _testcapi.float_pack
unpack = _testcapi.float_unpack
for endian in (BIG_ENDIAN, LITTLE_ENDIAN):
with self.subTest(endian=endian):
byteorder = "big" if endian == BIG_ENDIAN else "little"
# Convert sNaN to qNaN, if payload got truncated
data = make_nan(8, 0, False, 0x80001).to_bytes(8, byteorder)
snan_low = unpack(data, endian)
qnan4 = make_nan(4, 0, True, 0).to_bytes(4, byteorder)
qnan2 = make_nan(2, 0, True, 0).to_bytes(2, byteorder)
self.assertEqual(pack(4, snan_low, endian), qnan4)
self.assertEqual(pack(2, snan_low, endian), qnan2)
# Preserve NaN type, if payload not truncated
data = make_nan(8, 0, False, 0x80000000001).to_bytes(8, byteorder)
snan_high = unpack(data, endian)
snan4 = make_nan(4, 0, False, 16384).to_bytes(4, byteorder)
snan2 = make_nan(2, 0, False, 2).to_bytes(2, byteorder)
self.assertEqual(pack(4, snan_high, endian), snan4)
self.assertEqual(pack(2, snan_high, endian), snan2)
if __name__ == "__main__":
unittest.main()