diff --git a/include/itertools.hpp b/include/itertools.hpp
index 0ffeba65..f7d2b430 100644
--- a/include/itertools.hpp
+++ b/include/itertools.hpp
@@ -3,9 +3,57 @@
 #ifndef RGBDS_ITERTOOLS_HPP
 #define RGBDS_ITERTOOLS_HPP
 
+#include <deque>
+#include <optional>
+#include <stddef.h>
+#include <string>
 #include <tuple>
+#include <unordered_map>
 #include <utility>
 
+template<typename T>
+class InsertionOrderedMap {
+	std::deque<T> list;
+	std::unordered_map<std::string, size_t> map; // Indexes into `list`
+
+public:
+	size_t size() const { return list.size(); }
+
+	bool empty() const { return list.empty(); }
+
+	bool contains(std::string const &name) const { return map.find(name) != map.end(); }
+
+	T &operator[](size_t i) { return list[i]; }
+
+	typename decltype(list)::iterator begin() { return list.begin(); }
+	typename decltype(list)::iterator end() { return list.end(); }
+	typename decltype(list)::const_iterator begin() const { return list.begin(); }
+	typename decltype(list)::const_iterator end() const { return list.end(); }
+
+	T &add(std::string const &name) {
+		map[name] = list.size();
+		return list.emplace_back();
+	}
+
+	T &add(std::string const &name, T &&value) {
+		map[name] = list.size();
+		list.emplace_back(std::move(value));
+		return list.back();
+	}
+
+	T &addAnonymous() {
+		// Add the new item to the list, but do not update the map
+		return list.emplace_back();
+	}
+
+	std::optional<size_t> findIndex(std::string const &name) const {
+		if (auto search = map.find(name); search != map.end()) {
+			return search->second;
+		}
+		return std::nullopt;
+	}
+};
+
 template<typename T>
 class EnumSeq {
 	T _start;
diff --git a/src/asm/charmap.cpp b/src/asm/charmap.cpp
index f2ab2778..cd999cc1 100644
--- a/src/asm/charmap.cpp
+++ b/src/asm/charmap.cpp
@@ -2,7 +2,6 @@
 
 #include "asm/charmap.hpp"
 
-#include <deque>
 #include <map>
 #include <optional>
 #include <stack>
@@ -12,12 +11,12 @@
 #include <string.h>
 #include <string>
 #include <string_view>
-#include <unordered_map>
 #include <utility>
 #include <vector>
 
 #include "extern/utf8decoder.hpp"
 #include "helpers.hpp"
+#include "itertools.hpp" // InsertionOrderedMap
 #include "util.hpp"
 
 #include "asm/warning.hpp"
@@ -59,8 +58,7 @@ bool forEachChar(Charmap const &charmap, F callback) {
 	return true;
 }
 
-static std::deque<Charmap> charmapList;
-static std::unordered_map<std::string, size_t> charmapMap; // Indexes into `charmapList`
+static InsertionOrderedMap<Charmap> charmaps;
 
 static Charmap *currentCharmap;
 static std::stack<Charmap *> charmapStack;
@@ -69,7 +67,7 @@ bool charmap_ForEach(
     void (*mapFunc)(std::string const &),
     void (*charFunc)(std::string const &, std::vector<int32_t>)
 ) {
-	for (Charmap const &charmap : charmapList) {
+	for (Charmap const &charmap : charmaps) {
 		std::map<size_t, std::string> mappings;
 		forEachChar(charmap, [&mappings](size_t nodeIdx, std::string const &mapping) {
 			mappings[nodeIdx] = mapping;
@@ -81,45 +79,41 @@ bool charmap_ForEach(
 			charFunc(mapping, charmap.nodes[nodeIdx].value);
 		}
 	}
-	return !charmapList.empty();
+	return !charmaps.empty();
 }
 
 void charmap_New(std::string const &name, std::string const *baseName) {
-	size_t baseIdx = SIZE_MAX;
+	std::optional<size_t> baseIdx = std::nullopt;
 
 	if (baseName != nullptr) {
-		if (auto search = charmapMap.find(*baseName); search == charmapMap.end()) {
+		baseIdx = charmaps.findIndex(*baseName);
+		if (!baseIdx) {
 			error("Undefined base charmap `%s`", baseName->c_str());
-		} else {
-			baseIdx = search->second;
 		}
 	}
 
-	if (charmapMap.find(name) != charmapMap.end()) {
+	if (charmaps.contains(name)) {
 		error("Charmap `%s` is already defined", name.c_str());
 		return;
 	}
 
 	// Init the new charmap's fields
-	charmapMap[name] = charmapList.size();
-	Charmap &charmap = charmapList.emplace_back();
-
-	if (baseIdx != SIZE_MAX) {
-		charmap.nodes = charmapList[baseIdx].nodes; // Copies `charmapList[baseIdx].nodes`
+	Charmap &charmap = charmaps.add(name);
+	charmap.name = name;
+	if (baseIdx) {
+		charmap.nodes = charmaps[*baseIdx].nodes; // Copies `charmaps[*baseIdx].nodes`
 	} else {
 		charmap.nodes.emplace_back(); // Zero-init the root node
 	}
 
-	charmap.name = name;
-
 	currentCharmap = &charmap;
 }
 
 void charmap_Set(std::string const &name) {
-	if (auto search = charmapMap.find(name); search == charmapMap.end()) {
-		error("Undefined charmap `%s`", name.c_str());
+	if (auto index = charmaps.findIndex(name); index) {
+		currentCharmap = &charmaps[*index];
 	} else {
-		currentCharmap = &charmapList[search->second];
+		error("Undefined charmap `%s`", name.c_str());
 	}
 }
 
diff --git a/src/asm/section.cpp b/src/asm/section.cpp
index bf5d2f9e..4b663134 100644
--- a/src/asm/section.cpp
+++ b/src/asm/section.cpp
@@ -14,11 +14,11 @@
 #include <stdlib.h>
 #include <string.h>
 #include <string>
-#include <unordered_map>
 #include <utility>
 #include <vector>
 
 #include "helpers.hpp"
+#include "itertools.hpp" // InsertionOrderedMap
 #include "linkdefs.hpp"
 
 #include "asm/fstack.hpp"
@@ -46,8 +46,7 @@ struct SectionStackEntry {
 };
 
 static Section *currentSection = nullptr;
-static std::deque<Section> sectionList;
-static std::unordered_map<std::string, size_t> sectionMap; // Indexes into `sectionList`
+static InsertionOrderedMap<Section> sections;
 
 static uint32_t curOffset; // Offset into the current section (see `sect_GetSymbolOffset`)
 
@@ -87,17 +86,17 @@ static bool requireCodeSection() {
 }
 
 size_t sect_CountSections() {
-	return sectionList.size();
+	return sections.size();
 }
 
 void sect_ForEach(void (*callback)(Section &)) {
-	for (Section &sect : sectionList) {
+	for (Section &sect : sections) {
 		callback(sect);
 	}
 }
 
 void sect_CheckSizes() {
-	for (Section const &sect : sectionList) {
+	for (Section const &sect : sections) {
 		if (uint32_t maxSize = sectionTypeInfo[sect.type].size; sect.size > maxSize) {
 			error(
 			    "Section \"%s\" grew too big (max size = 0x%" PRIX32 " bytes, reached 0x%" PRIX32
@@ -111,8 +110,8 @@ void sect_CheckSizes() {
 }
 
 Section *sect_FindSectionByName(std::string const &name) {
-	auto search = sectionMap.find(name);
-	return search != sectionMap.end() ? &sectionList[search->second] : nullptr;
+	auto index = sections.findIndex(name);
+	return index ? &sections[*index] : nullptr;
 }
 
 #define sectError(...) \
@@ -324,8 +323,7 @@ static Section *createSection(
     SectionModifier mod
 ) {
 	// Add the new section to the list
-	Section &sect = sectionList.emplace_back();
-	sectionMap.emplace(name, sectionMap.size());
+	Section &sect = sections.add(name);
 
 	sect.name = name;
 	sect.type = type;
@@ -349,9 +347,8 @@ static Section *createSection(
 }
 
 static Section *createSectionFragmentLiteral(Section const &parent) {
-	// Add the new section to the list, but do not update the map
-	Section &sect = sectionList.emplace_back();
-	assume(sectionMap.find(parent.name) != sectionMap.end());
+	assume(sections.contains(parent.name));
+	Section &sect = sections.addAnonymous();
 
 	sect.name = parent.name;
 	sect.type = parent.type;
@@ -478,9 +475,9 @@ static void changeSection() {
 uint32_t Section::getID() const {
 	// Section fragments share the same name but have different IDs, so search by identity
 	if (auto search =
-	        std::find_if(RANGE(sectionList), [this](Section const &s) { return &s == this; });
-	    search != sectionList.end()) {
-		return static_cast<uint32_t>(std::distance(sectionList.begin(), search));
+	        std::find_if(RANGE(sections), [this](Section const &s) { return &s == this; });
+	    search != sections.end()) {
+		return static_cast<uint32_t>(std::distance(sections.begin(), search));
 	}
 	return UINT32_MAX; // LCOV_EXCL_LINE
 }
diff --git a/src/link/section.cpp b/src/link/section.cpp
index 04368bfe..1bc848dd 100644
--- a/src/link/section.cpp
+++ b/src/link/section.cpp
@@ -13,16 +13,16 @@
 #include <vector>
 
 #include "helpers.hpp"
+#include "itertools.hpp" // InsertionOrderedMap
 #include "linkdefs.hpp"
 
 #include "link/main.hpp"
 #include "link/warning.hpp"
 
-static std::vector<std::unique_ptr<Section>> sectionList;
-static std::unordered_map<std::string, size_t> sectionMap; // Indexes into `sectionList`
+static InsertionOrderedMap<std::unique_ptr<Section>> sections;
 
 void sect_ForEach(void (*callback)(Section &)) {
-	for (std::unique_ptr<Section> &ptr : sectionList) {
+	for (std::unique_ptr<Section> &ptr : sections) {
 		callback(*ptr);
 	}
 }
@@ -198,7 +198,7 @@ static void mergeSections(Section &target, std::unique_ptr<Section> &&other) {
 }
 
 void sect_AddSection(std::unique_ptr<Section> &&section) {
-	// Check if the section already exists
+	// Check if the section already exists; if not, add it
 	if (Section *target = sect_GetSection(section->name); target) {
 		mergeSections(*target, std::move(section));
 	} else if (section->modifier == SECTION_UNION && sectTypeHasData(section->type)) {
@@ -208,15 +208,13 @@ void sect_AddSection(std::unique_ptr<Section> &&section) {
 		    sectionTypeInfo[section->type].name.c_str()
 		);
 	} else {
-		// If not, add it
-		sectionMap.emplace(section->name, sectionList.size());
-		sectionList.push_back(std::move(section));
+		sections.add(section->name, std::move(section));
 	}
 }
 
 Section *sect_GetSection(std::string const &name) {
-	auto search = sectionMap.find(name);
-	return search != sectionMap.end() ? sectionList[search->second].get() : nullptr;
+	auto index = sections.findIndex(name);
+	return index ? sections[*index].get() : nullptr;
 }
 
 static void doSanityChecks(Section &section) {