-*- Mode: diff -*-
--- a/core/fxcrt/fx_memory_wrappers.h	2025-02-13 13:38:35.761778900 +0100
+++ b/core/fxcrt/fx_memory_wrappers.h	2025-02-13 13:38:48.136654800 +0100
@@ -33,9 +33,6 @@
 template <class T, void* Alloc(size_t, size_t), void Free(void*)>
 struct FxPartitionAllocAllocator {
  public:
-  static_assert(std::is_arithmetic<T>::value || std::is_enum<T>::value ||
-                    IsFXDataPartitionException<T>::value,
-                "Only numeric types allowed in this partition");
 
   using value_type = T;
   using pointer = T*;
diff --git a/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp b/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp
index a8e9e6090..0c341ab7f 100644
--- a/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp
+++ b/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp
@@ -289,7 +289,7 @@ void CloneResourcesDictEntries(CPDF_Document* doc,
           pdfium::Contains(kResourceKeys, key)) {
         RetainPtr<const CPDF_Object> direct_object = object->GetDirect();
         if (direct_object) {
-          entries_to_maybe_clone.emplace_back(key, std::move(direct_object));
+          entries_to_maybe_clone.push_back(KeyAndObject{key, std::move(direct_object)});
         }
       }
     }
diff --git a/core/fxcrt/numerics/safe_conversions_impl.h b/core/fxcrt/numerics/safe_conversions_impl.h
index b51078761..5e5d9fca7 100644
--- a/core/fxcrt/numerics/safe_conversions_impl.h
+++ b/core/fxcrt/numerics/safe_conversions_impl.h
@@ -373,7 +373,7 @@ INTEGER_FOR_DIGITS_AND_SIGN(uint64_t);
 
 template <size_t Size, bool IsSigned>
 using IntegerForDigitsAndSign =
-    IntegerForDigitsAndSignImpl<Size, IsSigned>::type;
+    typename IntegerForDigitsAndSignImpl<Size, IsSigned>::type;
 
 // WARNING: We have no IntegerForSizeAndSign<16, *>. If we ever add one to
 // support 128-bit math, then the ArithmeticPromotion template below will need
@@ -437,7 +437,7 @@ struct BigEnoughPromotionImpl<Lhs, Rhs, true, false> {
 };
 
 template <typename Lhs, typename Rhs>
-using BigEnoughPromotion = BigEnoughPromotionImpl<Lhs, Rhs>::type;
+using BigEnoughPromotion = typename BigEnoughPromotionImpl<Lhs, Rhs>::type;
 
 template <typename Lhs, typename Rhs>
 inline constexpr bool kIsBigEnoughPromotionContained =
@@ -480,7 +480,7 @@ struct FastIntegerArithmeticPromotionImpl<Lhs, Rhs> {
 
 template <typename Lhs, typename Rhs>
 using FastIntegerArithmeticPromotion =
-    FastIntegerArithmeticPromotionImpl<Lhs, Rhs>::type;
+    typename FastIntegerArithmeticPromotionImpl<Lhs, Rhs>::type;
 
 template <typename Lhs, typename Rhs>
 inline constexpr bool kIsFastIntegerArithmeticPromotionContained =
@@ -494,7 +494,7 @@ struct ArithmeticOrIntegralConstant {
 template <typename T>
   requires IntegralConstantLike<T>
 struct ArithmeticOrIntegralConstant<T> {
-  using type = T::value_type;
+  using type = typename T::value_type;
 };
 
 // Extracts the underlying type from an enum.
@@ -556,7 +556,7 @@ struct UnderlyingTypeImpl<StrictNumeric<T>> {
   using type = T;
 };
 template <typename T>
-using UnderlyingType = UnderlyingTypeImpl<T>::type;
+using UnderlyingType = typename UnderlyingTypeImpl<T>::type;
 
 template <typename T>
 inline constexpr bool kIsNumeric = std::is_arithmetic_v<UnderlyingType<T>>;
diff --git a/core/fpdfdoc/cpdf_nametree.cpp b/core/fpdfdoc/cpdf_nametree.cpp
index 47fae4b61..65e3e1c40 100644
--- a/core/fpdfdoc/cpdf_nametree.cpp
+++ b/core/fpdfdoc/cpdf_nametree.cpp
@@ -191,7 +191,7 @@ bool UpdateNodesAndLimitsUponDeletion(CPDF_Dictionary* pNode,
 }
 
 bool IsTraversedObject(const CPDF_Object* obj,
-                       absl::flat_hash_set<uint32_t>* seen_obj_nums) {
+                       std::set<uint32_t>* seen_obj_nums) {
   uint32_t obj_num = obj->GetObjNum();
   if (!obj_num) {
     return false;
@@ -202,7 +202,7 @@ bool IsTraversedObject(const CPDF_Object* obj,
 }
 
 bool IsArrayWithTraversedObject(const CPDF_Array* array,
-                                absl::flat_hash_set<uint32_t>* seen_obj_nums) {
+                                std::set<uint32_t>* seen_obj_nums) {
   if (IsTraversedObject(array, seen_obj_nums)) {
     return true;
   }
@@ -227,7 +227,7 @@ RetainPtr<const CPDF_Object> SearchNameNodeByNameInternal(
     int nLevel,
     size_t* nIndex,
     NodeToInsert* node_to_insert,
-    absl::flat_hash_set<uint32_t>* seen_obj_nums) {
+    std::set<uint32_t>* seen_obj_nums) {
   if (nLevel > kNameTreeMaxRecursion) {
     return nullptr;
   }
@@ -317,7 +317,7 @@ RetainPtr<const CPDF_Object> SearchNameNodeByName(
     const WideString& csName,
     NodeToInsert* node_to_insert) {
   size_t nIndex = 0;
-  absl::flat_hash_set<uint32_t> seen_obj_nums;
+  std::set<uint32_t> seen_obj_nums;
   return SearchNameNodeByNameInternal(pNode, csName, 0, &nIndex, node_to_insert,
                                       &seen_obj_nums);
 }
@@ -398,7 +398,7 @@ std::optional<IndexSearchResult> SearchNameNodeByIndex(
 // Get the total number of key-value pairs in the tree with root |pNode|.
 size_t CountNamesInternal(const CPDF_Dictionary* pNode,
                           int nLevel,
-                          absl::flat_hash_set<const CPDF_Dictionary*>& seen) {
+                          std::set<const CPDF_Dictionary*>& seen) {
   if (nLevel > kNameTreeMaxRecursion) {
     return 0;
   }
@@ -535,7 +535,7 @@ RetainPtr<const CPDF_Array> CPDF_NameTree::LookupNamedDest(
 }
 
 size_t CPDF_NameTree::GetCount() const {
-  absl::flat_hash_set<const CPDF_Dictionary*> seen;
+  std::set<const CPDF_Dictionary*> seen;
   return CountNamesInternal(root_.Get(), 0, seen);
 }
 
diff --git a/core/fxcrt/span.h b/core/fxcrt/span.h
index bad07b723..b960f90b4 100644
--- a/core/fxcrt/span.h
+++ b/core/fxcrt/span.h
@@ -791,9 +791,6 @@ class GSL_POINTER span {
   template <typename OtherElementType,
             size_t OtherExtent,
             typename OtherInternalPtrType>
-    requires((OtherExtent == dynamic_extent || extent == OtherExtent) &&
-             std::equality_comparable_with<const element_type,
-                                           const OtherElementType>)
   friend constexpr bool operator==(
       span lhs,
       span<OtherElementType, OtherExtent, OtherInternalPtrType> rhs) {
@@ -826,9 +823,6 @@ class GSL_POINTER span {
   template <typename OtherElementType,
             size_t OtherExtent,
             typename OtherInternalPtrType>
-    requires((OtherExtent == dynamic_extent || extent == OtherExtent) &&
-             std::three_way_comparable_with<const element_type,
-                                            const OtherElementType>)
   friend constexpr auto operator<=>(
       span lhs,
       span<OtherElementType, OtherExtent, OtherInternalPtrType> rhs) {