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[3.14] gh-145633: Fix struct.pack('f') on s390x (GH-146422) (#146460)

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gh-145633: Fix struct.pack('f') on s390x (GH-146422)

Use PyFloat_Pack4() to raise OverflowError.
Add more tests on packing/unpacking floats.
(cherry picked from commit 8de70b31c5)

Co-authored-by: Victor Stinner <vstinner@python.org>
Co-authored-by: Sergey B Kirpichev <skirpichev@gmail.com>
This commit is contained in:
Miss Islington (bot) 2026-03-26 12:38:42 +01:00 • committed by GitHub
parent 7efa72a6e4
commit 8a25840a2a
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3 changed files with 37 additions and 3 deletions
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33
Lib/test/test_struct.py
View file

@ -397,6 +397,21 @@ def test_705836(self):
big = (1 << 25) - 1
big = math.ldexp(big, 127 - 24)
self.assertRaises(OverflowError, struct.pack, ">f", big)
self.assertRaises(OverflowError, struct.pack, "<f", big)
# same for native format, see gh-145633
self.assertRaises(OverflowError, struct.pack, "f", big)
# And for half-floats
big = (1 << 11) - 1
big = math.ldexp(big, 15 - 10)
packed = struct.pack(">e", big)
unpacked = struct.unpack(">e", packed)[0]
self.assertEqual(big, unpacked)
big = (1 << 12) - 1
big = math.ldexp(big, 15 - 11)
self.assertRaises(OverflowError, struct.pack, ">e", big)
self.assertRaises(OverflowError, struct.pack, "<e", big)
self.assertRaises(OverflowError, struct.pack, "e", big)
def test_1530559(self):
for code, byteorder in iter_integer_formats():
@ -862,6 +877,24 @@ def test_operations_on_half_initialized_Struct(self):
self.assertRaises(RuntimeError, repr, S)
self.assertEqual(S.size, -1)
def test_float_round_trip(self):
for format in (
"f", "<f", ">f",
"d", "<d", ">d",
"e", "<e", ">e",
):
with self.subTest(format=format):
f = struct.unpack(format, struct.pack(format, 1.5))[0]
self.assertEqual(f, 1.5)
f = struct.unpack(format, struct.pack(format, NAN))[0]
self.assertTrue(math.isnan(f), f)
f = struct.unpack(format, struct.pack(format, INF))[0]
self.assertTrue(math.isinf(f), f)
self.assertEqual(math.copysign(1.0, f), 1.0)
f = struct.unpack(format, struct.pack(format, -INF))[0]
self.assertTrue(math.isinf(f), f)
self.assertEqual(math.copysign(1.0, f), -1.0)
class UnpackIteratorTest(unittest.TestCase):
"""

2
Misc/NEWS.d/next/Library/2026-03-26-11-04-42.gh-issue-145633.RWjlaX.rst Normal file
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@ -0,0 +1,2 @@
Fix ``struct.pack('f', float)``: use :c:func:`PyFloat_Pack4` to raise
:exc:`OverflowError`. Patch by Sergey B Kirpichev and Victor Stinner.

5
Modules/_struct.c
View file

@ -762,14 +762,13 @@ np_halffloat(_structmodulestate *state, char *p, PyObject *v, const formatdef *f
static int
np_float(_structmodulestate *state, char *p, PyObject *v, const formatdef *f)
{
float x = (float)PyFloat_AsDouble(v);
double x = PyFloat_AsDouble(v);
if (x == -1 && PyErr_Occurred()) {
PyErr_SetString(state->StructError,
"required argument is not a float");
return -1;
}
memcpy(p, &x, sizeof x);
return 0;
return PyFloat_Pack4(x, p, PY_LITTLE_ENDIAN);
}
static int