From 328b5f90858f93344ebc1484df8cadfd2a5da6dd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Antonio=20S=C3=A1nchez?= <cantonios@google.com>
Date: Tue, 15 Aug 2023 15:58:41 +0000
Subject: [PATCH] Add temporary macro to allow unaligned scalar UB.

---
 Eigen/src/Core/MapBase.h | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/Eigen/src/Core/MapBase.h b/Eigen/src/Core/MapBase.h
index 4bd29cf84..20a0154f9 100644
--- a/Eigen/src/Core/MapBase.h
+++ b/Eigen/src/Core/MapBase.h
@@ -193,8 +193,12 @@ template<typename Derived> class MapBase<Derived, ReadOnlyAccessors>
     EIGEN_DEVICE_FUNC
     void checkSanity(std::enable_if_t<(internal::traits<T>::Alignment>0),void*> = 0) const
     {
+// Temporary macro to allow scalars to not be properly aligned.  This is while we sort out failures
+// in TensorFlow Lite that are currently relying on this UB.
+#ifndef EIGEN_ALLOW_UNALIGNED_SCALARS
       // 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");
+#endif
 #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);
@@ -207,7 +211,12 @@ 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"); }
+    {
+#ifndef EIGEN_ALLOW_UNALIGNED_SCALARS
+      // 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");
+#endif
+    }
 
     PointerType m_data;
     const internal::variable_if_dynamic<Index, RowsAtCompileTime> m_rows;