71 lines
3.1 KiB
Diff
71 lines
3.1 KiB
Diff
From 80071371601233408b4d919dfe7cc05cfee93d02 Mon Sep 17 00:00:00 2001
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From: AnkitAhlawat <Ankit.Ahlawat@ibm.com>
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Date: Thu, 30 Apr 2026 19:18:10 +0530
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Subject: [PATCH] BUG: Fix signed overflow issue in npy_gcd for INT_MIN on
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s390x (#31360)
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This PR fixes signed overflow issue in npy_gcd when one of the inputs is the minimum value of a signed integer type (INT_MIN) on s390x architecture.
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issue was the expression a < 0 ? -a : a in npy_math_internal.h.src causes undefined behavior when a = INT_MIN because negating INT_MIN overflows a signed integer on s390x. i see it is working fine with other arch so fix only provided to s390x
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---
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numpy/_core/src/npymath/npy_math_internal.h.src | 11 ++++++++++-
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numpy/_core/tests/test_umath.py | 12 ++++++++----
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2 files changed, 18 insertions(+), 5 deletions(-)
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diff --git a/numpy/_core/src/npymath/npy_math_internal.h.src b/numpy/_core/src/npymath/npy_math_internal.h.src
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index 2f38497..787f7e6 100644
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--- a/numpy/_core/src/npymath/npy_math_internal.h.src
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+++ b/numpy/_core/src/npymath/npy_math_internal.h.src
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@@ -650,12 +650,21 @@ npy_lcm@c@(@type@ a, @type@ b)
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*
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* #type = (npy_int, npy_long, npy_longlong)*2#
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* #c = (,l,ll)*2#
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+ * #utype = (npy_uint, npy_ulong, npy_ulonglong)*2#
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* #func=gcd*3,lcm*3#
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*/
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NPY_INPLACE @type@
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npy_@func@@c@(@type@ a, @type@ b)
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{
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- return npy_@func@u@c@(a < 0 ? -a : a, b < 0 ? -b : b);
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+ /*
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+ * Cast to unsigned to avoid overflow when negating minimum signed value.
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+ * For negative values, cast to unsigned first, then apply negation in
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+ * unsigned arithmetic to avoid undefined behavior.
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+ * This ensures correct behavior across all architectures. #31359
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+ */
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+ @utype@ a_abs = a < 0 ? (@utype@)(0) - (@utype@)a : (@utype@)a;
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+ @utype@ b_abs = b < 0 ? (@utype@)(0) - (@utype@)b : (@utype@)b;
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+ return (@type@)npy_@func@u@c@(a_abs, b_abs);
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}
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/**end repeat**/
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diff --git a/numpy/_core/tests/test_umath.py b/numpy/_core/tests/test_umath.py
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index 8eac236..1575dd6 100644
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--- a/numpy/_core/tests/test_umath.py
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+++ b/numpy/_core/tests/test_umath.py
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@@ -4131,13 +4131,17 @@ def test_lcm_overflow(self):
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assert_equal(np.lcm(a, b), 10 * big)
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def test_gcd_overflow(self):
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- for dtype in (np.int32, np.int64):
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- # verify that we don't overflow when taking abs(x)
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- # not relevant for lcm, where the result is unrepresentable anyway
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- a = dtype(np.iinfo(dtype).min) # negative power of two
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+ # verify that we don't overflow when taking abs(x) for INT_MIN
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+ # this was undefined behavior that manifested on s390x with GCC 11.5
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+ for dtype in (np.int8, np.int16, np.int32, np.int64):
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+ a = dtype(np.iinfo(dtype).min) # INT_MIN
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q = -(a // 4)
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+ # Test with INT_MIN as first argument
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assert_equal(np.gcd(a, q * 3), q)
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assert_equal(np.gcd(a, -q * 3), q)
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+ # Test with INT_MIN as second argument
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+ assert_equal(np.gcd(q * 3, a), q)
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+ assert_equal(np.gcd(-q * 3, a), q)
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def test_decimal(self):
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from decimal import Decimal
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--
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2.54.0
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