https://bugs.gentoo.org/924387
https://code.wildfiregames.com/D5219

Index: ps/trunk/libraries/source/fcollada/src/FCollada/FUtils/FUXmlDocument.cpp
===================================================================
--- ps/libraries/source/fcollada/src/FCollada/FUtils/FUXmlDocument.cpp
+++ ps/libraries/source/fcollada/src/FCollada/FUtils/FUXmlDocument.cpp
@@ -2,7 +2,7 @@
 	Copyright (C) 2005-2007 Feeling Software Inc.
 	Portions of the code are:
 	Copyright (C) 2005-2007 Sony Computer Entertainment America
-	
+
 	MIT License: http://www.opensource.org/licenses/mit-license.php
 */
 
@@ -13,10 +13,12 @@
 #include "FUFile.h"
 #include "FCDocument/FCDocument.h"
 
+#include <libxml/parser.h>
+
 #define MAX_FILE_SIZE 10240000
 //
 // FUXmlDocument
-// 
+//
 
 FUXmlDocument::FUXmlDocument(FUFileManager* manager, const fchar* _filename, bool _isParsing)
 :	isParsing(_isParsing), filename(_filename)
Index: ps/libraries/source/fcollada/src/FColladaPlugins/FArchiveXML/FArchiveXML.cpp
===================================================================
--- ps/libraries/source/fcollada/src/FColladaPlugins/FArchiveXML/FArchiveXML.cpp
+++ ps/libraries/source/fcollada/src/FColladaPlugins/FArchiveXML/FArchiveXML.cpp
@@ -2,7 +2,7 @@
 	Copyright (C) 2005-2007 Feeling Software Inc.
 	Portions of the code are:
 	Copyright (C) 2005-2007 Sony Computer Entertainment America
-	
+
 	MIT License: http://www.opensource.org/licenses/mit-license.php
 */
 
@@ -77,6 +77,7 @@
 #include "FCDocument/FCDVersion.h"
 #include "FUtils/FUXmlDocument.h"
 
+#include <libxml/xmlIO.h>
 
 //
 // Constants
@@ -442,7 +443,7 @@
 	}
 
 	if (status) FUError::Error(FUError::DEBUG_LEVEL, FUError::DEBUG_LOAD_SUCCESSFUL);
-	return status;	
+	return status;
 }
 
 bool FArchiveXML::ExportFile(FCDocument* fcdocument, const fchar* filePath)
@@ -515,13 +516,13 @@
 	xmlOutputBufferPtr buf = xmlAllocOutputBuffer(NULL);
 	xmlNodeDumpOutput(buf, rootNode->doc, rootNode, 0, 0, NULL);
 
-#ifdef LIBXML2_NEW_BUFFER
-	outData.resize(xmlOutputBufferGetSize(buf) * sizeof(xmlChar));
-	memcpy(outData.begin(), xmlOutputBufferGetContent(buf), outData.size());
-#else
-	outData.resize(buf->buffer->use * sizeof(xmlChar));
-	memcpy(outData.begin(), buf->buffer->content, outData.size());
-#endif
+#ifdef LIBXML2_NEW_BUFFER
+	outData.resize(xmlOutputBufferGetSize(buf) * sizeof(xmlChar));
+	memcpy(outData.begin(), xmlOutputBufferGetContent(buf), outData.size());
+#else
+	outData.resize(buf->buffer->use * sizeof(xmlChar));
+	memcpy(outData.begin(), buf->buffer->content, outData.size());
+#endif
 
 	xmlOutputBufferClose(buf);
 	daeDocument.ReleaseXmlData();
@@ -591,7 +592,7 @@
 		else if (IsEquivalent(child->name, DAE_LIBRARY_PMATERIAL_ELEMENT)) n.order = PHYSICS_MATERIAL;
 		else if (IsEquivalent(child->name, DAE_LIBRARY_PMODEL_ELEMENT)) n.order = PHYSICS_MODEL;
 		else if (IsEquivalent(child->name, DAE_LIBRARY_PSCENE_ELEMENT)) n.order = PHYSICS_SCENE;
-		else if (IsEquivalent(child->name, DAE_ASSET_ELEMENT)) 
+		else if (IsEquivalent(child->name, DAE_ASSET_ELEMENT))
 		{
 			// Read in the asset information
 			status &= (FArchiveXML::LoadAsset(theDocument->GetAsset(), child));
@@ -679,9 +680,9 @@
 		case IMAGE: status &= (FArchiveXML::LoadImageLibrary(theDocument->GetImageLibrary(), n.node)); break;
 		case LIGHT: status &= (FArchiveXML::LoadLightLibrary(theDocument->GetLightLibrary(), n.node)); break;
 		case MATERIAL: status &= (FArchiveXML::LoadMaterialLibrary(theDocument->GetMaterialLibrary(), n.node)); break;
-		case PHYSICS_MODEL: 
+		case PHYSICS_MODEL:
 			{
-				status &= (FArchiveXML::LoadPhysicsModelLibrary(theDocument->GetPhysicsModelLibrary(), n.node)); 
+				status &= (FArchiveXML::LoadPhysicsModelLibrary(theDocument->GetPhysicsModelLibrary(), n.node));
 				size_t physicsModelCount = theDocument->GetPhysicsModelLibrary()->GetEntityCount();
 				for (size_t physicsModelCounter = 0; physicsModelCounter < physicsModelCount; physicsModelCounter++)
 				{
@@ -790,7 +791,7 @@
 	{
 		// [staylor] Why is this done here?  Shouldn't it be in FCDExternalReferenceManager?
 		// If it is, change it, either way delete the FUAssert (thanks)
-		//FUAssert(false == true, ;);  
+		// FUAssert(false == true, ;);
 		FArchiveXML::RegisterLoadedDocument(theDocument);
 		//FCDExternalReferenceManager::RegisterLoadedDocument(theDocument);
 	}
@@ -891,14 +892,14 @@
 			// Export the emitter library
 			xmlNode* libraryNode = AddChild(typedTechniqueNode, DAE_LIBRARY_EMITTER_ELEMENT);
 
-			if (!theDocument->GetEmitterLibrary()->GetTransientFlag()) 
+			if (!theDocument->GetEmitterLibrary()->GetTransientFlag())
 				FArchiveXML::WriteLibrary(theDocument->GetEmitterLibrary(), libraryNode);
 		}
 
 		// Write out the animations
 		if (animationLibraryNode != NULL)
 		{
-			if (!theDocument->GetAnimationLibrary()->GetTransientFlag()) 
+			if (!theDocument->GetAnimationLibrary()->GetTransientFlag())
 				FArchiveXML::WriteLibrary(theDocument->GetAnimationLibrary(), animationLibraryNode);
 		}
 
@@ -978,7 +979,7 @@
 	{
 		return FArchiveXML::WriteSwitch(object, &objectType->GetParent(), node);
 	}
-	else 
+	else
 	{
 		FUBreak;
 		return NULL;
@@ -986,7 +987,7 @@
 }
 
 bool FArchiveXML::LoadAnimationLibrary(FCDObject* object, xmlNode* node)
-{ 
+{
 	return FArchiveXML::LoadLibrary<FCDAnimation>(object, node);
 }
 
@@ -996,17 +997,17 @@
 }
 
 bool FArchiveXML::LoadCameraLibrary(FCDObject* object, xmlNode* node)
-{ 
+{
 	return FArchiveXML::LoadLibrary<FCDCamera>(object, node);
 }
 
 bool FArchiveXML::LoadControllerLibrary(FCDObject* object, xmlNode* node)
-{ 
+{
 	return FArchiveXML::LoadLibrary<FCDController>(object, node);
 }
 
 bool FArchiveXML::LoadEffectLibrary(FCDObject* object, xmlNode* node)
-{ 
+{
 	return FArchiveXML::LoadLibrary<FCDEffect>(object, node);
 }
 
@@ -1016,7 +1017,7 @@
 }
 
 bool FArchiveXML::LoadForceFieldLibrary(FCDObject* object, xmlNode* node)
-{ 
+{
 	return FArchiveXML::LoadLibrary<FCDForceField>(object, node);
 }
 
Index: ps/source/collada/CommonConvert.cpp
===================================================================
--- ps/source/collada/CommonConvert.cpp
+++ ps/source/collada/CommonConvert.cpp
@@ -1,4 +1,4 @@
-/* Copyright (C) 2018 Wildfire Games.
+/* Copyright (C) 2023 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -28,8 +28,9 @@
 #include "FUtils/FUDaeSyntax.h"
 #include "FUtils/FUFileManager.h"
 
-#include <cassert>
 #include <algorithm>
+#include <cassert>
+#include <libxml/xmlerror.h>
 
 void require_(int line, bool value, const char* type, const char* message)
 {
Index: ps/source/collada/XMLFix.cpp
===================================================================
--- ps/source/collada/XMLFix.cpp
+++ ps/source/collada/XMLFix.cpp
@@ -1,4 +1,4 @@
-/* Copyright (C) 2009 Wildfire Games.
+/* Copyright (C) 2023 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -23,6 +23,8 @@
 
 #include "FUtils/FUXmlParser.h"
 
+#include <libxml/parser.h>
+
 /*
 
 Things that are fixed here:
Index: ps/source/ps/XML/RelaxNG.cpp
===================================================================
--- ps/source/ps/XML/RelaxNG.cpp
+++ ps/source/ps/XML/RelaxNG.cpp
@@ -1,4 +1,4 @@
-/* Copyright (C) 2021 Wildfire Games.
+/* Copyright (C) 2023 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -25,9 +25,11 @@
 #include "ps/CStr.h"
 #include "ps/Filesystem.h"
 
+#include <libxml/parser.h>
 #include <libxml/relaxng.h>
 #include <map>
 #include <mutex>
+#include <type_traits>
 
 TIMER_ADD_CLIENT(xml_validation);
 
@@ -46,7 +48,8 @@
 	g_SchemaCache.clear();
 }
 
-static void relaxNGErrorHandler(void* UNUSED(userData), xmlErrorPtr error)
+static void relaxNGErrorHandler(void* UNUSED(userData),
+	std::conditional_t<LIBXML_VERSION >= 21200, const xmlError, xmlError>* error)
 {
 	// Strip a trailing newline
 	std::string message = error->message;
Index: ps/source/ps/XML/Xeromyces.cpp
===================================================================
--- ps/source/ps/XML/Xeromyces.cpp
+++ ps/source/ps/XML/Xeromyces.cpp
@@ -1,4 +1,4 @@
-/* Copyright (C) 2021 Wildfire Games.
+/* Copyright (C) 2023 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -33,12 +33,14 @@
 #include "Xeromyces.h"
 
 #include <libxml/parser.h>
+#include <type_traits>
 
 static std::mutex g_ValidatorCacheLock;
 static std::map<const std::string, RelaxNGValidator> g_ValidatorCache;
 static bool g_XeromycesStarted = false;
 
-static void errorHandler(void* UNUSED(userData), xmlErrorPtr error)
+static void errorHandler(void* UNUSED(userData),
+	std::conditional_t<LIBXML_VERSION >= 21200, const xmlError, xmlError>* error)
 {
 	// Strip a trailing newline
 	std::string message = error->message;