ue4_25-defines-fix.patch

diff --git a/Engine/Source/Programs/UnrealBuildTool/Configuration/UEBuildModuleCPP.cs b/Engine/Source/Programs/UnrealBuildTool/Configuration/UEBuildModuleCPP.cs
index 4c0428ad373..6a6d4f71397 100644
--- a/Engine/Source/Programs/UnrealBuildTool/Configuration/UEBuildModuleCPP.cs
+++ b/Engine/Source/Programs/UnrealBuildTool/Configuration/UEBuildModuleCPP.cs
@@ -404,6 +404,10 @@ namespace UnrealBuildTool
 
 			// Write all the definitions to a separate file
 			CreateHeaderForDefinitions(CompileEnvironment, IntermediateDirectory, null, Graph);
+			if (CompileEnvironment.Definitions.Count > 0)
+			{
+				CompileEnvironment.Definitions.Clear();
+			}
 
 			// Mapping of source file to unity file. We output this to intermediate directories for other tools (eg. live coding) to use.
 			Dictionary<FileItem, FileItem> SourceFileToUnityFile = new Dictionary<FileItem, FileItem>();
@@ -874,6 +878,10 @@ namespace UnrealBuildTool
 		{
 			// Write all the definitions out to a separate file
 			CreateHeaderForDefinitions(CompileEnvironment, IntermediateDirectory, "Adaptive", Graph);
+			if (CompileEnvironment.Definitions.Count > 0)
+			{
+				CompileEnvironment.Definitions.Clear();
+			}
 
 			// Compile the files
 			return ToolChain.CompileCPPFiles(CompileEnvironment, Files, IntermediateDirectory, ModuleName, Graph);
@@ -886,6 +894,10 @@ namespace UnrealBuildTool
 
 			// Write all the definitions out to a separate file
 			CreateHeaderForDefinitions(CompileEnvironment, IntermediateDirectory, "Adaptive", Graph);
+			if (CompileEnvironment.Definitions.Count > 0)
+			{
+				CompileEnvironment.Definitions.Clear();
+			}
 
 			// Compile the files
 			return ToolChain.CompileCPPFiles(CompileEnvironment, Files, IntermediateDirectory, ModuleName, Graph);
@@ -1001,7 +1013,7 @@ namespace UnrealBuildTool
 						}
 
 						CompileEnvironment = new CppCompileEnvironment(CompileEnvironment);
-						CompileEnvironment.Definitions.Clear();
+						// CompileEnvironment.Definitions.Clear(); // @todo: Do not clear definitions prior to end of their usefulness
 						CompileEnvironment.ForceIncludeFiles.Add(PrivateDefinitionsFileItem);
 						CompileEnvironment.PrecompiledHeaderAction = PrecompiledHeaderAction.Include;
 						CompileEnvironment.PrecompiledHeaderIncludeFilename = Instance.HeaderFile.Location;
@@ -1039,7 +1051,7 @@ namespace UnrealBuildTool
 				using (StringWriter Writer = new StringWriter())
 				{
 					WriteDefinitions(CompileEnvironment.Definitions, Writer);
-					CompileEnvironment.Definitions.Clear();
+					//CompileEnvironment.Definitions.Clear(); @todo: Do not clear definitions prior to end of their usefulness
 
 					FileItem PrivateDefinitionsFileItem = Graph.CreateIntermediateTextFile(PrivateDefinitionsFile, Writer.ToString());
 					CompileEnvironment.ForceIncludeFiles.Add(PrivateDefinitionsFileItem);