diff --git a/Eigen/src/Core/PlainObjectBase.h b/Eigen/src/Core/PlainObjectBase.h
index f9bf737ca..58783850f 100644
--- a/Eigen/src/Core/PlainObjectBase.h
+++ b/Eigen/src/Core/PlainObjectBase.h
@@ -31,6 +31,7 @@ namespace Eigen {
 
 namespace internal {
 
+#ifndef EIGEN_NO_DEBUG
 template <int MaxSizeAtCompileTime, int MaxRowsAtCompileTime, int MaxColsAtCompileTime>
 struct check_rows_cols_for_overflow {
   EIGEN_STATIC_ASSERT(MaxRowsAtCompileTime* MaxColsAtCompileTime == MaxSizeAtCompileTime,
@@ -44,7 +45,7 @@ struct check_rows_cols_for_overflow<Dynamic, MaxRowsAtCompileTime, Dynamic> {
   template <typename Index>
   EIGEN_DEVICE_FUNC static EIGEN_ALWAYS_INLINE constexpr void run(Index, Index cols) {
     constexpr Index MaxIndex = NumTraits<Index>::highest();
-    bool error = cols > MaxIndex / MaxRowsAtCompileTime;
+    bool error = cols > (MaxIndex / MaxRowsAtCompileTime);
     if (error) throw_std_bad_alloc();
   }
 };
@@ -54,7 +55,7 @@ struct check_rows_cols_for_overflow<Dynamic, Dynamic, MaxColsAtCompileTime> {
   template <typename Index>
   EIGEN_DEVICE_FUNC static EIGEN_ALWAYS_INLINE constexpr void run(Index rows, Index) {
     constexpr Index MaxIndex = NumTraits<Index>::highest();
-    bool error = rows > MaxIndex / MaxColsAtCompileTime;
+    bool error = rows > (MaxIndex / MaxColsAtCompileTime);
     if (error) throw_std_bad_alloc();
   }
 };
@@ -64,10 +65,11 @@ struct check_rows_cols_for_overflow<Dynamic, Dynamic, Dynamic> {
   template <typename Index>
   EIGEN_DEVICE_FUNC static EIGEN_ALWAYS_INLINE constexpr void run(Index rows, Index cols) {
     constexpr Index MaxIndex = NumTraits<Index>::highest();
-    bool error = cols == 0 ? false : (rows > MaxIndex / cols);
+    bool error = cols == 0 ? false : (rows > (MaxIndex / cols));
     if (error) throw_std_bad_alloc();
   }
 };
+#endif
 
 template <typename Derived, typename OtherDerived = Derived,
           bool IsVector = bool(Derived::IsVectorAtCompileTime) && bool(OtherDerived::IsVectorAtCompileTime)>
@@ -297,8 +299,10 @@ class PlainObjectBase : public internal::dense_xpr_base<Derived>::type
                  internal::check_implication(ColsAtCompileTime == Dynamic && MaxColsAtCompileTime != Dynamic,
                                              cols <= MaxColsAtCompileTime) &&
                  rows >= 0 && cols >= 0 && "Invalid sizes when resizing a matrix or array.");
+#ifndef EIGEN_NO_DEBUG
     internal::check_rows_cols_for_overflow<MaxSizeAtCompileTime, MaxRowsAtCompileTime, MaxColsAtCompileTime>::run(rows,
                                                                                                                   cols);
+#endif
 #ifdef EIGEN_INITIALIZE_COEFFS
     Index size = rows * cols;
     bool size_changed = size != this->size();
@@ -367,8 +371,10 @@ class PlainObjectBase : public internal::dense_xpr_base<Derived>::type
   template <typename OtherDerived>
   EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void resizeLike(const EigenBase<OtherDerived>& _other) {
     const OtherDerived& other = _other.derived();
+#ifndef EIGEN_NO_DEBUG
     internal::check_rows_cols_for_overflow<MaxSizeAtCompileTime, MaxRowsAtCompileTime, MaxColsAtCompileTime>::run(
         other.rows(), other.cols());
+#endif
     const Index othersize = other.rows() * other.cols();
     if (RowsAtCompileTime == 1) {
       eigen_assert(other.rows() == 1 || other.cols() == 1);
@@ -941,8 +947,10 @@ struct conservative_resize_like_impl {
         ((Derived::IsRowMajor && _this.cols() == cols) ||  // row-major and we change only the number of rows
          (!Derived::IsRowMajor && _this.rows() == rows)))  // column-major and we change only the number of columns
     {
+#ifndef EIGEN_NO_DEBUG
       internal::check_rows_cols_for_overflow<Derived::MaxSizeAtCompileTime, Derived::MaxRowsAtCompileTime,
                                              Derived::MaxColsAtCompileTime>::run(rows, cols);
+#endif
       _this.derived().m_storage.conservativeResize(rows * cols, rows, cols);
     } else {
       // The storage order does not allow us to use reallocation.
diff --git a/unsupported/Eigen/CXX11/src/Tensor/Tensor.h b/unsupported/Eigen/CXX11/src/Tensor/Tensor.h
index 3b9eff7f0..9417469d2 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/Tensor.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/Tensor.h
@@ -303,12 +303,16 @@ class Tensor : public TensorBase<Tensor<Scalar_, NumIndices_, Options_, IndexTyp
 
   /** Normal Dimension */
   EIGEN_DEVICE_FUNC void resize(const array<Index, NumIndices>& dimensions) {
-    int i;
+#ifndef EIGEN_NO_DEBUG
     Index size = Index(1);
-    for (i = 0; i < NumIndices; i++) {
+    for (int i = 0; i < NumIndices; i++) {
       internal::check_rows_cols_for_overflow<Dynamic, Dynamic, Dynamic>::run(size, dimensions[i]);
       size *= dimensions[i];
     }
+#else
+    Index size = internal::array_prod(dimensions);
+#endif
+
 #ifdef EIGEN_INITIALIZE_COEFFS
     bool size_changed = size != this->size();
     m_storage.resize(size, dimensions);
@@ -318,15 +322,6 @@ class Tensor : public TensorBase<Tensor<Scalar_, NumIndices_, Options_, IndexTyp
 #endif
   }
 
-  // Why this overload, DSizes is derived from array ??? //
-  EIGEN_DEVICE_FUNC void resize(const DSizes<Index, NumIndices>& dimensions) {
-    array<Index, NumIndices> dims;
-    for (int i = 0; i < NumIndices; ++i) {
-      dims[i] = dimensions[i];
-    }
-    resize(dims);
-  }
-
   EIGEN_DEVICE_FUNC void resize() {
     EIGEN_STATIC_ASSERT(NumIndices == 0, YOU_MADE_A_PROGRAMMING_MISTAKE);
     // Nothing to do: rank 0 tensors have fixed size
@@ -347,7 +342,6 @@ class Tensor : public TensorBase<Tensor<Scalar_, NumIndices_, Options_, IndexTyp
     resize(internal::customIndices2Array<Index, NumIndices>(dimensions));
   }
 
-#ifndef EIGEN_EMULATE_CXX11_META_H
   template <typename std::ptrdiff_t... Indices>
   EIGEN_DEVICE_FUNC void resize(const Sizes<Indices...>& dimensions) {
     array<Index, NumIndices> dims;
@@ -356,16 +350,6 @@ class Tensor : public TensorBase<Tensor<Scalar_, NumIndices_, Options_, IndexTyp
     }
     resize(dims);
   }
-#else
-  template <std::size_t V1, std::size_t V2, std::size_t V3, std::size_t V4, std::size_t V5>
-  EIGEN_DEVICE_FUNC void resize(const Sizes<V1, V2, V3, V4, V5>& dimensions) {
-    array<Index, NumIndices> dims;
-    for (int i = 0; i < NumIndices; ++i) {
-      dims[i] = static_cast<Index>(dimensions[i]);
-    }
-    resize(dims);
-  }
-#endif
 
 #ifdef EIGEN_TENSOR_PLUGIN
 #include EIGEN_TENSOR_PLUGIN
diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorBroadcasting.h b/unsupported/Eigen/CXX11/src/Tensor/TensorBroadcasting.h
index 6c91d938f..9ef4bbce0 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorBroadcasting.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorBroadcasting.h
@@ -55,12 +55,10 @@ template <>
 struct is_input_scalar<Sizes<>> {
   static const bool value = true;
 };
-#ifndef EIGEN_EMULATE_CXX11_META_H
 template <typename std::ptrdiff_t... Indices>
 struct is_input_scalar<Sizes<Indices...>> {
-  static const bool value = (Sizes<Indices...>::total_size == 1);
+  static constexpr bool value = (Sizes<Indices...>::total_size == 1);
 };
-#endif
 
 }  // end namespace internal
 
diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorDimensions.h b/unsupported/Eigen/CXX11/src/Tensor/TensorDimensions.h
index 4043e5eba..ae8f25f87 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorDimensions.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorDimensions.h
@@ -81,7 +81,6 @@ struct fixed_size_tensor_index_extraction_helper<Index, 0> {
 }  // end namespace internal
 
 // Fixed size
-#ifndef EIGEN_EMULATE_CXX11_META_H
 template <typename std::ptrdiff_t... Indices>
 struct Sizes {
   typedef internal::numeric_list<std::ptrdiff_t, Indices...> Base;
@@ -133,87 +132,6 @@ EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE std::ptrdiff_t array_prod(const Sizes<Indi
 }
 }  // namespace internal
 
-#else
-
-template <std::ptrdiff_t n>
-struct non_zero_size {
-  typedef internal::type2val<std::ptrdiff_t, n> type;
-};
-template <>
-struct non_zero_size<0> {
-  typedef internal::null_type type;
-};
-
-template <std::ptrdiff_t V1 = 0, std::ptrdiff_t V2 = 0, std::ptrdiff_t V3 = 0, std::ptrdiff_t V4 = 0,
-          std::ptrdiff_t V5 = 0>
-struct Sizes {
-  typedef typename internal::make_type_list<typename non_zero_size<V1>::type, typename non_zero_size<V2>::type,
-                                            typename non_zero_size<V3>::type, typename non_zero_size<V4>::type,
-                                            typename non_zero_size<V5>::type>::type Base;
-  static const std::ptrdiff_t count = Base::count;
-  static const std::ptrdiff_t total_size = internal::arg_prod<Base>::value;
-
-  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE ptrdiff_t rank() const { return count; }
-
-  static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE ptrdiff_t TotalSize() { return internal::arg_prod<Base>::value; }
-
-  Sizes() {}
-  template <typename DenseIndex>
-  explicit Sizes(const array<DenseIndex, Base::count>& /*indices*/) {
-    // todo: add assertion
-  }
-
-  template <typename T>
-  Sizes& operator=(const T& /*other*/) {
-    // add assertion failure if the size of other is different
-    return *this;
-  }
-
-  template <typename... DenseIndex>
-  Sizes(DenseIndex... /*indices*/) {}
-  explicit Sizes(std::initializer_list<std::ptrdiff_t>) {
-    // todo: add assertion
-  }
-
-  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Index operator[](const Index index) const {
-    switch (index) {
-      case 0:
-        return internal::get<0, Base>::value;
-      case 1:
-        return internal::get<1, Base>::value;
-      case 2:
-        return internal::get<2, Base>::value;
-      case 3:
-        return internal::get<3, Base>::value;
-      case 4:
-        return internal::get<4, Base>::value;
-      default:
-        eigen_assert(false && "index overflow");
-        return static_cast<Index>(-1);
-    }
-  }
-
-  template <typename DenseIndex>
-  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE ptrdiff_t IndexOfColMajor(const array<DenseIndex, Base::count>& indices) const {
-    return internal::fixed_size_tensor_index_linearization_helper<DenseIndex, Base::count, Base::count, false>::run(
-        indices, *reinterpret_cast<const Base*>(this));
-  }
-  template <typename DenseIndex>
-  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE ptrdiff_t IndexOfRowMajor(const array<DenseIndex, Base::count>& indices) const {
-    return internal::fixed_size_tensor_index_linearization_helper<DenseIndex, Base::count, Base::count, true>::run(
-        indices, *reinterpret_cast<const Base*>(this));
-  }
-};
-
-namespace internal {
-template <std::ptrdiff_t V1, std::ptrdiff_t V2, std::ptrdiff_t V3, std::ptrdiff_t V4, std::ptrdiff_t V5>
-EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE std::ptrdiff_t array_prod(const Sizes<V1, V2, V3, V4, V5>&) {
-  return Sizes<V1, V2, V3, V4, V5>::total_size;
-}
-}  // namespace internal
-
-#endif
-
 // Boilerplate
 namespace internal {
 template <typename Index, std::ptrdiff_t NumIndices, std::ptrdiff_t n, bool RowMajor>
@@ -289,21 +207,12 @@ struct DSizes : array<DenseIndex, NumDims> {
     }
   }
 
-#ifndef EIGEN_EMULATE_CXX11_META_H
   template <typename std::ptrdiff_t... Indices>
   EIGEN_DEVICE_FUNC DSizes(const Sizes<Indices...>& a) {
     for (int i = 0; i < NumDims; ++i) {
       (*this)[i] = a[i];
     }
   }
-#else
-  template <std::ptrdiff_t V1, std::ptrdiff_t V2, std::ptrdiff_t V3, std::ptrdiff_t V4, std::ptrdiff_t V5>
-  EIGEN_DEVICE_FUNC DSizes(const Sizes<V1, V2, V3, V4, V5>& a) {
-    for (int i = 0; i < NumDims; ++i) {
-      (*this)[i] = a[i];
-    }
-  }
-#endif
 
   template <typename... IndexTypes>
       EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE explicit DSizes(DenseIndex firstDimension, DenseIndex secondDimension,
@@ -374,7 +283,6 @@ template <typename DenseIndex, int NumDims>
 struct array_size<DSizes<DenseIndex, NumDims> > {
   static const ptrdiff_t value = NumDims;
 };
-#ifndef EIGEN_EMULATE_CXX11_META_H
 template <typename std::ptrdiff_t... Indices>
 struct array_size<const Sizes<Indices...> > {
   static const std::ptrdiff_t value = Sizes<Indices...>::count;
@@ -392,22 +300,6 @@ EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE std::ptrdiff_t array_get(const Sizes<>&) {
   eigen_assert(false && "should never be called");
   return -1;
 }
-#else
-template <std::ptrdiff_t V1, std::ptrdiff_t V2, std::ptrdiff_t V3, std::ptrdiff_t V4, std::ptrdiff_t V5>
-struct array_size<const Sizes<V1, V2, V3, V4, V5> > {
-  static const ptrdiff_t value = Sizes<V1, V2, V3, V4, V5>::count;
-};
-template <std::ptrdiff_t V1, std::ptrdiff_t V2, std::ptrdiff_t V3, std::ptrdiff_t V4, std::ptrdiff_t V5>
-struct array_size<Sizes<V1, V2, V3, V4, V5> > {
-  static const ptrdiff_t value = Sizes<V1, V2, V3, V4, V5>::count;
-};
-template <std::ptrdiff_t n, std::ptrdiff_t V1, std::ptrdiff_t V2, std::ptrdiff_t V3, std::ptrdiff_t V4,
-          std::ptrdiff_t V5>
-EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE std::ptrdiff_t array_get(const Sizes<V1, V2, V3, V4, V5>&) {
-  return get<n, typename Sizes<V1, V2, V3, V4, V5>::Base>::value;
-}
-
-#endif
 
 template <typename Dims1, typename Dims2, ptrdiff_t n, ptrdiff_t m>
 struct sizes_match_below_dim {
diff --git a/unsupported/Eigen/CXX11/src/Tensor/TensorIndexList.h b/unsupported/Eigen/CXX11/src/Tensor/TensorIndexList.h
index fe83b268d..69ab6840c 100644
--- a/unsupported/Eigen/CXX11/src/Tensor/TensorIndexList.h
+++ b/unsupported/Eigen/CXX11/src/Tensor/TensorIndexList.h
@@ -37,7 +37,7 @@ namespace Eigen {
 
 template <Index n>
 struct type2index {
-  static const Index value = n;
+  static constexpr Index value = n;
   EIGEN_DEVICE_FUNC constexpr operator Index() const { return n; }
   EIGEN_DEVICE_FUNC void set(Index val) { eigen_assert(val == n); }
 };
@@ -46,8 +46,8 @@ struct type2index {
 // such as IndexPairList<type2indexpair<1,2>, type2indexpair<3,4>>().
 template <Index f, Index s>
 struct type2indexpair {
-  static const Index first = f;
-  static const Index second = s;
+  static constexpr Index first = f;
+  static constexpr Index second = s;
 
   constexpr EIGEN_DEVICE_FUNC operator IndexPair<Index>() const { return IndexPair<Index>(f, s); }
 
@@ -134,7 +134,7 @@ struct IndexTuple<T, O...> {
   EIGEN_DEVICE_FUNC constexpr IndexTuple() : head(), others() {}
   EIGEN_DEVICE_FUNC constexpr IndexTuple(const T& v, const O... o) : head(v), others(o...) {}
 
-  constexpr static int count = 1 + sizeof...(O);
+  static constexpr int count = 1 + sizeof...(O);
   T head;
   IndexTuple<O...> others;
   typedef T Head;
@@ -194,11 +194,11 @@ EIGEN_DEVICE_FUNC constexpr const typename IndexTupleExtractor<N, T, O...>::ValT
 }
 template <typename T, typename... O>
 struct array_size<IndexTuple<T, O...>> {
-  static const size_t value = IndexTuple<T, O...>::count;
+  static constexpr size_t value = IndexTuple<T, O...>::count;
 };
 template <typename T, typename... O>
 struct array_size<const IndexTuple<T, O...>> {
-  static const size_t value = IndexTuple<T, O...>::count;
+  static constexpr size_t value = IndexTuple<T, O...>::count;
 };
 
 template <Index Idx, typename ValueT>
diff --git a/unsupported/test/cxx11_tensor_concatenation.cpp b/unsupported/test/cxx11_tensor_concatenation.cpp
index 68455b34d..562ac779b 100644
--- a/unsupported/test/cxx11_tensor_concatenation.cpp
+++ b/unsupported/test/cxx11_tensor_concatenation.cpp
@@ -47,13 +47,7 @@ static void test_static_dimension_failure() {
 
   // This can be worked around in this case.
   Tensor<int, 3, DataLayout> concatenation = left.reshape(Tensor<int, 3>::Dimensions(2, 3, 1)).concatenate(right, 0);
-  Tensor<int, 2, DataLayout> alternative = left
-                                               // Clang compiler break with {{{}}} with an ambiguous error on copy
-                                               // constructor the variadic DSize constructor added for #ifndef
-                                               // EIGEN_EMULATE_CXX11_META_H. Solution: either the code should change to
-                                               //  Tensor<int, 2>::Dimensions{{2, 3}}
-                                               // or Tensor<int, 2>::Dimensions{Tensor<int, 2>::Dimensions{{2, 3}}}
-                                               .concatenate(right.reshape(Tensor<int, 2>::Dimensions(2, 3)), 0);
+  Tensor<int, 2, DataLayout> alternative = left.concatenate(right.reshape(Tensor<int, 2>::Dimensions(2, 3)), 0);
 }
 
 template <int DataLayout>