diff --git a/Eigen/Cholesky b/Eigen/Cholesky
index b05ed8278..e75357a65 100644
--- a/Eigen/Cholesky
+++ b/Eigen/Cholesky
@@ -14,8 +14,6 @@
 #include "src/Core/util/DisableStupidWarnings.h"
 
 /** \defgroup Cholesky_Module Cholesky module
- *
- *
  *
  * This module provides two variants of the Cholesky decomposition for selfadjoint (hermitian) matrices.
  * Those decompositions are also accessible via the following methods:
diff --git a/Eigen/CholmodSupport b/Eigen/CholmodSupport
index adc5f8d63..31725138b 100644
--- a/Eigen/CholmodSupport
+++ b/Eigen/CholmodSupport
@@ -26,7 +26,7 @@
  * For the sake of completeness, this module also propose the two following classes:
  * - class CholmodSimplicialLLT
  * - class CholmodSimplicialLDLT
- * Note that these classes does not bring any particular advantage compared to the built-in
+ * Note that these classes do not bring any particular advantage compared to the built-in
  * SimplicialLLT and SimplicialLDLT factorization classes.
  *
  * \code
diff --git a/Eigen/Core b/Eigen/Core
index 5c9aa37b6..fa33b9672 100644
--- a/Eigen/Core
+++ b/Eigen/Core
@@ -36,12 +36,6 @@
 #include <new>
 #endif
 
-// Disable the ipa-cp-clone optimization flag with MinGW 6.x or older (enabled by default with -O3)
-// See http://eigen.tuxfamily.org/bz/show_bug.cgi?id=556 for details.
-#if EIGEN_COMP_MINGW && EIGEN_GNUC_STRICT_LESS_THAN(6, 0, 0)
-#pragma GCC optimize("-fno-ipa-cp-clone")
-#endif
-
 // Prevent ICC from specializing std::complex operators that silently fail
 // on device. This allows us to use our own device-compatible specializations
 // instead.
@@ -53,7 +47,7 @@
 // this include file manages BLAS and MKL related macros
 // and inclusion of their respective header files
 #include "src/Core/util/MKL_support.h"
-#include "src/Core/util/AOCL_Support.h"    // ← ADD THIS
+#include "src/Core/util/AOCL_Support.h"
 
 
 #if defined(EIGEN_HAS_CUDA_FP16) || defined(EIGEN_HAS_HIP_FP16)
@@ -73,8 +67,7 @@
 #include <omp.h>
 #endif
 
-// MSVC for windows mobile does not have the errno.h file
-#if !(EIGEN_COMP_MSVC && EIGEN_OS_WINCE) && !EIGEN_COMP_ARM
+#if !EIGEN_COMP_ARM
 #define EIGEN_HAS_ERRNO
 #endif
 
@@ -125,7 +118,7 @@
 
 // required for __cpuid, needs to be included after cmath
 // also required for _BitScanReverse on Windows on ARM
-#if EIGEN_COMP_MSVC && (EIGEN_ARCH_i386_OR_x86_64 || EIGEN_ARCH_ARM64) && !EIGEN_OS_WINCE
+#if EIGEN_COMP_MSVC && (EIGEN_ARCH_i386_OR_x86_64 || EIGEN_ARCH_ARM64)
 #include <intrin.h>
 #endif
 
@@ -155,19 +148,9 @@
 #endif
 #endif
 
-#if defined EIGEN2_SUPPORT_STAGE40_FULL_EIGEN3_STRICTNESS || defined EIGEN2_SUPPORT_STAGE30_FULL_EIGEN3_API || \
-    defined EIGEN2_SUPPORT_STAGE20_RESOLVE_API_CONFLICTS || defined EIGEN2_SUPPORT_STAGE10_FULL_EIGEN2_API ||  \
-    defined EIGEN2_SUPPORT
-// This will generate an error message:
-#error Eigen2-support is only available up to version 3.2. Please go to "http://eigen.tuxfamily.org/index.php?title=Eigen2" for further information
-#endif
-
 namespace Eigen {
 
-// we use size_t frequently and we'll never remember to prepend it with std:: every time just to
-// ensure QNX/QCC support
 using std::size_t;
-// gcc 4.6.0 wants std:: for ptrdiff_t
 using std::ptrdiff_t;
 
 }  // namespace Eigen
@@ -373,8 +356,6 @@ using std::ptrdiff_t;
 #include "src/Core/DenseStorage.h"
 #include "src/Core/NestByValue.h"
 
-// #include "src/Core/ForceAlignedAccess.h"
-
 #include "src/Core/ReturnByValue.h"
 #include "src/Core/NoAlias.h"
 #include "src/Core/PlainObjectBase.h"
diff --git a/Eigen/Dense b/Eigen/Dense
index 5768910bd..c90db7657 100644
--- a/Eigen/Dense
+++ b/Eigen/Dense
@@ -1,3 +1,13 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef EIGEN_DENSE_MODULE_H
+#define EIGEN_DENSE_MODULE_H
+
 #include "Core"
 #include "LU"
 #include "Cholesky"
@@ -5,3 +15,5 @@
 #include "SVD"
 #include "Geometry"
 #include "Eigenvalues"
+
+#endif  // EIGEN_DENSE_MODULE_H
diff --git a/Eigen/Eigen b/Eigen/Eigen
index 654c8dc63..bb8f02f04 100644
--- a/Eigen/Eigen
+++ b/Eigen/Eigen
@@ -1,2 +1,14 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef EIGEN_EIGEN_MODULE_H
+#define EIGEN_EIGEN_MODULE_H
+
 #include "Dense"
 #include "Sparse"
+
+#endif  // EIGEN_EIGEN_MODULE_H
diff --git a/Eigen/Eigenvalues b/Eigen/Eigenvalues
index 60d0d5396..f68eb8542 100644
--- a/Eigen/Eigenvalues
+++ b/Eigen/Eigenvalues
@@ -11,8 +11,6 @@
 #include "Core"
 
 #include "Cholesky"
-#include "Jacobi"
-#include "Householder"
 #include "LU"
 #include "Geometry"
 #include "Sparse"  // Needed by ComplexQZ.
@@ -20,8 +18,6 @@
 #include "src/Core/util/DisableStupidWarnings.h"
 
 /** \defgroup Eigenvalues_Module Eigenvalues module
- *
- *
  *
  * This module mainly provides various eigenvalue solvers.
  * This module also provides some MatrixBase methods, including:
diff --git a/Eigen/Geometry b/Eigen/Geometry
index fd81ae2c7..c3ddb3d8a 100644
--- a/Eigen/Geometry
+++ b/Eigen/Geometry
@@ -12,7 +12,6 @@
 
 #include "SVD"
 #include "LU"
-#include <limits>
 
 #include "src/Core/util/DisableStupidWarnings.h"
 
diff --git a/Eigen/KLUSupport b/Eigen/KLUSupport
index 13959a3c8..6a5c59710 100644
--- a/Eigen/KLUSupport
+++ b/Eigen/KLUSupport
@@ -29,7 +29,7 @@ extern "C" {
  * \endcode
  *
  * In order to use this module, the klu and btf headers must be accessible from the include paths, and your binary must
- * be linked to the klu library and its dependencies. The dependencies depend on how umfpack has been compiled. For a
+ * be linked to the klu library and its dependencies. The dependencies depend on how KLU has been compiled. For a
  * cmake based project, you can use our FindKLU.cmake module to help you in this task.
  *
  */
diff --git a/Eigen/LU b/Eigen/LU
index d46bacf4b..ea54e353e 100644
--- a/Eigen/LU
+++ b/Eigen/LU
@@ -23,11 +23,10 @@
  * \endcode
  */
 
+// IWYU pragma: begin_exports
 #include "src/misc/Kernel.h"
 #include "src/misc/Image.h"
 #include "src/misc/RankRevealingBase.h"
-
-// IWYU pragma: begin_exports
 #include "src/LU/FullPivLU.h"
 #include "src/LU/PartialPivLU.h"
 #ifdef EIGEN_USE_LAPACKE
diff --git a/Eigen/PaStiXSupport b/Eigen/PaStiXSupport
index dd1cfcb12..59442316e 100644
--- a/Eigen/PaStiXSupport
+++ b/Eigen/PaStiXSupport
@@ -36,7 +36,7 @@ extern "C" {
  * \endcode
  *
  * In order to use this module, the PaSTiX headers must be accessible from the include paths, and your binary must be
- * linked to the PaSTiX library and its dependencies. This wrapper resuires PaStiX version 5.x compiled without MPI
+ * linked to the PaSTiX library and its dependencies. This wrapper requires PaStiX version 5.x compiled without MPI
  * support. The dependencies depend on how PaSTiX has been compiled. For a cmake based project, you can use our
  * FindPaSTiX.cmake module to help you in this task.
  *
diff --git a/Eigen/QR b/Eigen/QR
index 78c05632e..b29abce9b 100644
--- a/Eigen/QR
+++ b/Eigen/QR
@@ -11,14 +11,11 @@
 #include "Core"
 
 #include "Cholesky"
-#include "Jacobi"
 #include "Householder"
 
 #include "src/Core/util/DisableStupidWarnings.h"
 
 /** \defgroup QR_Module QR module
- *
- *
  *
  * This module provides various QR decompositions
  * This module also provides some MatrixBase methods, including:
diff --git a/Eigen/QtAlignedMalloc b/Eigen/QtAlignedMalloc
index 585f8e81c..6e15b26e6 100644
--- a/Eigen/QtAlignedMalloc
+++ b/Eigen/QtAlignedMalloc
@@ -14,11 +14,11 @@
 
 #include "src/Core/util/DisableStupidWarnings.h"
 
-void *qMalloc(std::size_t size) { return Eigen::internal::aligned_malloc(size); }
+inline void *qMalloc(std::size_t size) { return Eigen::internal::aligned_malloc(size); }
 
-void qFree(void *ptr) { Eigen::internal::aligned_free(ptr); }
+inline void qFree(void *ptr) { Eigen::internal::aligned_free(ptr); }
 
-void *qRealloc(void *ptr, std::size_t size) {
+inline void *qRealloc(void *ptr, std::size_t size) {
   void *newPtr = Eigen::internal::aligned_malloc(size);
   std::memcpy(newPtr, ptr, size);
   Eigen::internal::aligned_free(ptr);
diff --git a/Eigen/SPQRSupport b/Eigen/SPQRSupport
index c01dbe009..bfc2e7bfa 100644
--- a/Eigen/SPQRSupport
+++ b/Eigen/SPQRSupport
@@ -38,4 +38,4 @@
 
 #include "src/Core/util/ReenableStupidWarnings.h"
 
-#endif
+#endif  // EIGEN_SPQRSUPPORT_MODULE_H
diff --git a/Eigen/SVD b/Eigen/SVD
index 40ac3d01e..ef5e36e82 100644
--- a/Eigen/SVD
+++ b/Eigen/SVD
@@ -9,14 +9,10 @@
 #define EIGEN_SVD_MODULE_H
 
 #include "QR"
-#include "Householder"
-#include "Jacobi"
 
 #include "src/Core/util/DisableStupidWarnings.h"
 
 /** \defgroup SVD_Module SVD module
- *
- *
  *
  * This module provides SVD decomposition for matrices (both real and complex).
  * Two decomposition algorithms are provided:
diff --git a/Eigen/SparseCore b/Eigen/SparseCore
index 56a9401af..6020e4285 100644
--- a/Eigen/SparseCore
+++ b/Eigen/SparseCore
@@ -12,11 +12,7 @@
 
 #include "src/Core/util/DisableStupidWarnings.h"
 
-#include <vector>
 #include <map>
-#include <cstdlib>
-#include <cstring>
-#include <algorithm>
 #include <numeric>
 
 /**
diff --git a/Eigen/SparseQR b/Eigen/SparseQR
index b4f1cad6b..1ad51923c 100644
--- a/Eigen/SparseQR
+++ b/Eigen/SparseQR
@@ -35,4 +35,4 @@
 
 #include "src/Core/util/ReenableStupidWarnings.h"
 
-#endif
+#endif  // EIGEN_SPARSEQR_MODULE_H
diff --git a/Eigen/SuperLUSupport b/Eigen/SuperLUSupport
index 79e2222f4..27e14d29e 100644
--- a/Eigen/SuperLUSupport
+++ b/Eigen/SuperLUSupport
@@ -16,6 +16,7 @@
 #define EIGEN_EMPTY_WAS_ALREADY_DEFINED
 #endif
 
+// Required by SuperLU headers, which expect int_t to be defined as a global typedef.
 typedef int int_t;
 #include <slu_Cnames.h>
 #include <supermatrix.h>
diff --git a/Eigen/ThreadPool b/Eigen/ThreadPool
index 39e5d1eec..ac08bef03 100644
--- a/Eigen/ThreadPool
+++ b/Eigen/ThreadPool
@@ -27,7 +27,7 @@
 
 #include <cstddef>
 #include <cstring>
-#include <time.h>
+#include <ctime>
 
 #include <vector>
 #include <atomic>
@@ -77,4 +77,4 @@
 
 #include "src/Core/util/ReenableStupidWarnings.h"
 
-#endif  // EIGEN_CXX11_THREADPOOL_MODULE_H
+#endif  // EIGEN_THREADPOOL_MODULE_H
diff --git a/Eigen/UmfPackSupport b/Eigen/UmfPackSupport
index 126344cba..28e386fad 100644
--- a/Eigen/UmfPackSupport
+++ b/Eigen/UmfPackSupport
@@ -35,7 +35,7 @@ extern "C" {
 
 // IWYU pragma: begin_exports
 #include "src/UmfPackSupport/UmfPackSupport.h"
-// IWYU pragma: endexports
+// IWYU pragma: end_exports
 
 #include "src/Core/util/ReenableStupidWarnings.h"
 
diff --git a/Eigen/Version b/Eigen/Version
index 164c87f62..c10836318 100644
--- a/Eigen/Version
+++ b/Eigen/Version
@@ -1,3 +1,10 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
 #ifndef EIGEN_VERSION_H
 #define EIGEN_VERSION_H