From 8115b45e503705d01fae5d4e1e23cc92c0dda87b Mon Sep 17 00:00:00 2001
From: Rasmus Munk Larsen <4643818-rmlarsen1@users.noreply.gitlab.com>
Date: Fri, 20 Mar 2026 17:27:02 -0700
Subject: [PATCH] Fix integer sanitizer issues in shifts and test ranges

libeigen/eigen!2320

Co-authored-by: Rasmus Munk Larsen <rmlarsen@gmail.com>
---
 Eigen/src/Core/MathFunctions.h |  3 ++-
 test/numext.cpp                | 18 +++++++++++++++---
 test/product.h                 | 11 ++++++++++-
 test/redux.cpp                 |  7 ++++++-
 4 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/Eigen/src/Core/MathFunctions.h b/Eigen/src/Core/MathFunctions.h
index 54da17cc1..c428a58f3 100644
--- a/Eigen/src/Core/MathFunctions.h
+++ b/Eigen/src/Core/MathFunctions.h
@@ -1923,7 +1923,8 @@ EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE double fmod(const double& a, const double&
 
 template <typename Scalar, typename Enable = std::enable_if_t<std::is_integral<Scalar>::value>>
 EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Scalar logical_shift_left(const Scalar& a, int n) {
-  return a << n;
+  using UnsignedScalar = typename numext::get_integer_by_size<sizeof(Scalar)>::unsigned_type;
+  return bit_cast<Scalar, UnsignedScalar>(bit_cast<UnsignedScalar, Scalar>(a) << n);
 }
 
 template <typename Scalar, typename Enable = std::enable_if_t<std::is_integral<Scalar>::value>>
diff --git a/test/numext.cpp b/test/numext.cpp
index ebe9fb069..98ffdcc4f 100644
--- a/test/numext.cpp
+++ b/test/numext.cpp
@@ -44,6 +44,19 @@ void check_negate() {
   }
 }
 
+template <typename T>
+std::enable_if_t<NumTraits<T>::IsInteger, T> random_abs2_input() {
+  const T safeAbs2Input = static_cast<T>(std::sqrt(static_cast<long double>(NumTraits<T>::highest())));
+  return NumTraits<T>::IsSigned ? internal::random<T>(-safeAbs2Input, safeAbs2Input)
+                                : internal::random<T>(T(0), safeAbs2Input);
+}
+
+template <typename T>
+std::enable_if_t<!NumTraits<T>::IsInteger, T> random_abs2_input() {
+  typedef typename NumTraits<T>::Real Real;
+  return internal::random<T>() / Real(2);
+}
+
 template <typename T>
 void check_abs() {
   typedef typename NumTraits<T>::Real Real;
@@ -54,8 +67,7 @@ void check_abs() {
   VERIFY_IS_EQUAL(numext::abs(T(1)), T(1));
 
   for (int k = 0; k < 100; ++k) {
-    T x = internal::random<T>();
-    x = x / Real(2);
+    T x = random_abs2_input<T>();
     if (NumTraits<T>::IsSigned) {
       VERIFY_IS_EQUAL(numext::abs(x), numext::abs(numext::negate(x)));
       VERIFY(numext::abs(numext::negate(x)) >= zero);
@@ -301,7 +313,7 @@ void check_shift() {
     const T a = internal::random<T>();
     for (int s = 1; s < kNumBits; s++) {
       T a_bsll = numext::logical_shift_left(a, s);
-      T a_bsll_ref = a << s;
+      T a_bsll_ref = numext::bit_cast<T, UnsignedT>(numext::bit_cast<UnsignedT, T>(a) << s);
       VERIFY_IS_EQUAL(a_bsll, a_bsll_ref);
       T a_bsrl = numext::logical_shift_right(a, s);
       T a_bsrl_ref = numext::bit_cast<T, UnsignedT>(numext::bit_cast<UnsignedT, T>(a) >> s);
diff --git a/test/product.h b/test/product.h
index 00e67efe3..0449a5af7 100644
--- a/test/product.h
+++ b/test/product.h
@@ -81,15 +81,24 @@ void product(const MatrixType& m) {
 
   // Prevent overflows for integer types.
   if (Eigen::NumTraits<Scalar>::IsInteger) {
-    Scalar kMaxVal = Scalar(10000);
+    Scalar kMaxVal = Scalar(8);
     m1.array() = m1.array() - kMaxVal * (m1.array() / kMaxVal);
     m2.array() = m2.array() - kMaxVal * (m2.array() / kMaxVal);
+    square.array() = square.array() - kMaxVal * (square.array() / kMaxVal);
+    res.array() = res.array() - kMaxVal * (res.array() / kMaxVal);
+    square2.array() = square2.array() - kMaxVal * (square2.array() / kMaxVal);
+    res2.array() = res2.array() - kMaxVal * (res2.array() / kMaxVal);
     v1.array() = v1.array() - kMaxVal * (v1.array() / kMaxVal);
+    vc2.array() = vc2.array() - kMaxVal * (vc2.array() / kMaxVal);
   }
 
   OtherMajorMatrixType tm1 = m1;
 
   Scalar s1 = internal::random<Scalar>();
+  if (Eigen::NumTraits<Scalar>::IsInteger) {
+    Scalar kMaxVal = Scalar(8);
+    s1 = s1 - kMaxVal * (s1 / kMaxVal);
+  }
 
   Index r = internal::random<Index>(0, rows - 1), c = internal::random<Index>(0, cols - 1),
         c2 = internal::random<Index>(0, cols - 1);
diff --git a/test/redux.cpp b/test/redux.cpp
index ad3ff1fe2..d0cefb064 100644
--- a/test/redux.cpp
+++ b/test/redux.cpp
@@ -32,7 +32,7 @@ void matrixRedux(const MatrixType& m) {
   m2.setRandom();
   // Prevent overflows for integer types.
   if (Eigen::NumTraits<Scalar>::IsInteger) {
-    Scalar kMaxVal = Scalar(10000);
+    Scalar kMaxVal = Scalar(8);
     m1.array() = m1.array() - kMaxVal * (m1.array() / kMaxVal);
     m2.array() = m2.array() - kMaxVal * (m2.array() / kMaxVal);
   }
@@ -98,6 +98,11 @@ void vectorRedux(const VectorType& w) {
 
   VectorType v = VectorType::Random(size);
   VectorType v_for_prod = VectorType::Ones(size) + Scalar(0.2) * v;  // see comment above declaration of m1_for_prod
+  if (Eigen::NumTraits<Scalar>::IsInteger) {
+    Scalar kMaxVal = Scalar(8);
+    v.array() = v.array() - kMaxVal * (v.array() / kMaxVal);
+    v_for_prod = VectorType::Ones(size) + Scalar(0.2) * v;
+  }
 
   for (int i = 1; i < size; i++) {
     Scalar s(0), p(1);