From 0ae7d7a36117630f544f80a782f95b9f0a293659 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Antonio=20S=C3=A1nchez?= <cantonios@google.com>
Date: Tue, 1 Aug 2023 19:39:08 +0000
Subject: [PATCH] Fix unaligned scalar alignment UB.

---
 Eigen/src/Core/MapBase.h |  4 +++-
 test/mapped_matrix.cpp   | 34 ++++++----------------------------
 2 files changed, 9 insertions(+), 29 deletions(-)

diff --git a/Eigen/src/Core/MapBase.h b/Eigen/src/Core/MapBase.h
index 4dda24d21..4bd29cf84 100644
--- a/Eigen/src/Core/MapBase.h
+++ b/Eigen/src/Core/MapBase.h
@@ -193,6 +193,8 @@ template<typename Derived> class MapBase<Derived, ReadOnlyAccessors>
     EIGEN_DEVICE_FUNC
     void checkSanity(std::enable_if_t<(internal::traits<T>::Alignment>0),void*> = 0) const
     {
+      // Pointer must be aligned to the Scalar type, otherwise we get UB.
+      eigen_assert((std::uintptr_t(m_data) % alignof(Scalar) == 0) && "data is not scalar-aligned");
 #if EIGEN_MAX_ALIGN_BYTES>0
       // innerStride() is not set yet when this function is called, so we optimistically assume the lowest plausible value:
       const Index minInnerStride = InnerStrideAtCompileTime == Dynamic ? 1 : Index(InnerStrideAtCompileTime);
@@ -205,7 +207,7 @@ template<typename Derived> class MapBase<Derived, ReadOnlyAccessors>
     template<typename T>
     EIGEN_DEVICE_FUNC
     void checkSanity(std::enable_if_t<internal::traits<T>::Alignment==0,void*> = 0) const
-    {}
+    { eigen_assert((std::uintptr_t(m_data) % alignof(Scalar) == 0) && "data is not scalar-aligned"); }
 
     PointerType m_data;
     const internal::variable_if_dynamic<Index, RowsAtCompileTime> m_rows;
diff --git a/test/mapped_matrix.cpp b/test/mapped_matrix.cpp
index 7270d030b..f4638f6bc 100644
--- a/test/mapped_matrix.cpp
+++ b/test/mapped_matrix.cpp
@@ -68,12 +68,12 @@ template<typename MatrixType> void map_class_matrix(const MatrixType& m)
   Scalar array4[256];
   if(size<=256)
     for(int i = 0; i < size; i++) array4[i] = Scalar(1);
-  
+
   Map<MatrixType> map1(array1, rows, cols);
   Map<MatrixType, AlignedMax> map2(array2, rows, cols);
   Map<MatrixType> map3(array3unaligned, rows, cols);
   Map<MatrixType> map4(array4, rows, cols);
-  
+
   VERIFY_IS_EQUAL(map1, MatrixType::Ones(rows,cols));
   VERIFY_IS_EQUAL(map2, MatrixType::Ones(rows,cols));
   VERIFY_IS_EQUAL(map3, MatrixType::Ones(rows,cols));
@@ -88,17 +88,17 @@ template<typename MatrixType> void map_class_matrix(const MatrixType& m)
   VERIFY_IS_EQUAL(ma1, ma2);
   VERIFY_IS_EQUAL(ma1, ma3);
   VERIFY_IS_EQUAL(ma1, map3);
-  
+
   VERIFY_IS_APPROX(s1*map1, s1*map2);
   VERIFY_IS_APPROX(s1*ma1, s1*ma2);
   VERIFY_IS_EQUAL(s1*ma1, s1*ma3);
   VERIFY_IS_APPROX(s1*map1, s1*map3);
-  
+
   map2 *= s1;
   map3 *= s1;
   VERIFY_IS_APPROX(s1*map1, map2);
   VERIFY_IS_APPROX(s1*map1, map3);
-  
+
   if(size<=256)
   {
     VERIFY_IS_EQUAL(map4, MatrixType::Ones(rows,cols));
@@ -108,7 +108,7 @@ template<typename MatrixType> void map_class_matrix(const MatrixType& m)
     VERIFY_IS_EQUAL(ma1, map4);
     VERIFY_IS_EQUAL(ma1, ma4);
     VERIFY_IS_APPROX(s1*map1, s1*map4);
-    
+
     map4 *= s1;
     VERIFY_IS_APPROX(s1*map1, map4);
   }
@@ -159,27 +159,6 @@ template<typename PlainObjectType> void check_const_correctness(const PlainObjec
   VERIFY( !(Map<ConstPlainObjectType, AlignedMax>::Flags & LvalueBit) );
 }
 
-template<typename Scalar>
-void map_not_aligned_on_scalar()
-{
-  typedef Matrix<Scalar,Dynamic,Dynamic> MatrixType;
-  Index size = 11;
-  Scalar* array1 = internal::aligned_new<Scalar>((size+1)*(size+1)+1);
-  Scalar* array2 = reinterpret_cast<Scalar*>(sizeof(Scalar)/2+std::size_t(array1));
-  Map<MatrixType,0,OuterStride<> > map2(array2, size, size, OuterStride<>(size+1));
-  MatrixType m2 = MatrixType::Random(size,size);
-  map2 = m2;
-  VERIFY_IS_EQUAL(m2, map2);
-  
-  typedef Matrix<Scalar,Dynamic,1> VectorType;
-  Map<VectorType> map3(array2, size);
-  MatrixType v3 = VectorType::Random(size);
-  map3 = v3;
-  VERIFY_IS_EQUAL(v3, map3);
-  
-  internal::aligned_delete(array1, (size+1)*(size+1)+1);
-}
-
 EIGEN_DECLARE_TEST(mapped_matrix)
 {
   for(int i = 0; i < g_repeat; i++) {
@@ -204,6 +183,5 @@ EIGEN_DECLARE_TEST(mapped_matrix)
     CALL_SUBTEST_8( map_static_methods(RowVector3d()) );
     CALL_SUBTEST_9( map_static_methods(VectorXcd(8)) );
     CALL_SUBTEST_10( map_static_methods(VectorXf(12)) );
-    CALL_SUBTEST_11( map_not_aligned_on_scalar<double>() );
   }
 }