From 801a9ee6903e3e80b9cba5d03e0b68335d4f9828 Mon Sep 17 00:00:00 2001
From: Rasmus Munk Larsen <4643818-rmlarsen1@users.noreply.gitlab.com>
Date: Sun, 29 Mar 2026 21:05:49 -0700
Subject: [PATCH] Fix ~1,460 MSVC warnings from generic code instantiated with
 bool

libeigen/eigen!2364

Co-authored-by: Rasmus Munk Larsen <rmlarsen@gmail.com>
---
 Eigen/src/Core/RealView.h                         |  2 +-
 Eigen/src/Core/products/GeneralBlockPanelKernel.h | 11 +++++++++++
 Eigen/src/Core/products/GeneralMatrixVector.h     | 11 +++++++++++
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/Eigen/src/Core/RealView.h b/Eigen/src/Core/RealView.h
index 3be5556a8..59cd6d54e 100644
--- a/Eigen/src/Core/RealView.h
+++ b/Eigen/src/Core/RealView.h
@@ -72,7 +72,7 @@ struct evaluator<RealView<Xpr>> : private evaluator<Xpr> {
   static constexpr int CoeffReadCost = BaseEvaluator::CoeffReadCost;
   static constexpr int Alignment = BaseEvaluator::Alignment;
   static constexpr bool IsRowMajor = ExpressionTraits::IsRowMajor;
-  static constexpr bool DirectAccess = Flags & DirectAccessBit;
+  static constexpr bool DirectAccess = (Flags & DirectAccessBit) != 0;
 
   using ComplexCoeffReturnType = std::conditional_t<DirectAccess, const ComplexScalar&, ComplexScalar>;
   using CoeffReturnType = std::conditional_t<DirectAccess, const Scalar&, Scalar>;
diff --git a/Eigen/src/Core/products/GeneralBlockPanelKernel.h b/Eigen/src/Core/products/GeneralBlockPanelKernel.h
index 7314b2931..49dc85406 100644
--- a/Eigen/src/Core/products/GeneralBlockPanelKernel.h
+++ b/Eigen/src/Core/products/GeneralBlockPanelKernel.h
@@ -13,6 +13,13 @@
 // IWYU pragma: private
 #include "../InternalHeaderCheck.h"
 
+// C4804: unsafe use of type 'bool' in operation. Unavoidable in generic code
+// instantiated with bool scalars (e.g. += and * on bool).
+#if EIGEN_COMP_MSVC
+#pragma warning(push)
+#pragma warning(disable : 4804)
+#endif
+
 namespace Eigen {
 
 namespace internal {
@@ -2396,4 +2403,8 @@ inline void setCpuCacheSizes(std::ptrdiff_t l1, std::ptrdiff_t l2, std::ptrdiff_
 
 }  // end namespace Eigen
 
+#if EIGEN_COMP_MSVC
+#pragma warning(pop)
+#endif
+
 #endif  // EIGEN_GENERAL_BLOCK_PANEL_H
diff --git a/Eigen/src/Core/products/GeneralMatrixVector.h b/Eigen/src/Core/products/GeneralMatrixVector.h
index 40694f2e6..5f6c3958d 100644
--- a/Eigen/src/Core/products/GeneralMatrixVector.h
+++ b/Eigen/src/Core/products/GeneralMatrixVector.h
@@ -13,6 +13,13 @@
 // IWYU pragma: private
 #include "../InternalHeaderCheck.h"
 
+// C4804: unsafe use of type 'bool' in operation. Unavoidable in generic code
+// instantiated with bool scalars (e.g. += and * on bool).
+#if EIGEN_COMP_MSVC
+#pragma warning(push)
+#pragma warning(disable : 4804)
+#endif
+
 namespace Eigen {
 
 namespace internal {
@@ -672,4 +679,8 @@ general_matrix_vector_product<Index, LhsScalar, LhsMapper, RowMajor, ConjugateLh
 
 }  // end namespace Eigen
 
+#if EIGEN_COMP_MSVC
+#pragma warning(pop)
+#endif
+
 #endif  // EIGEN_GENERAL_MATRIX_VECTOR_H