Enable code coverage support on Unreal Built Tool Linux Toolchain

engine-coverage.patch

--- a/Engine/Source/Programs/UnrealBuildTool/Configuration/ModuleRules.cs
+++ b/Engine/Source/Programs/UnrealBuildTool/Configuration/ModuleRules.cs
@@ -606,6 +606,10 @@ namespace UnrealBuildTool
 		{
 			get
 			{
+				if (bCodeCoverage) {
+					return CodeOptimization.Never;
+				}
+
 				if (OptimizeCodeOverride.HasValue)
 					return OptimizeCodeOverride.Value;
 
@@ -703,6 +707,11 @@ namespace UnrealBuildTool
 		/// </summary>
 		public bool bUseRTTI = false;
 
+		/// <summary>
+		/// Enable code coverage compilation/linking support.
+		/// </summary>
+		public bool bCodeCoverage = false;
+
 		/// <summary>
 		/// Direct the compiler to generate AVX instructions wherever SSE or AVX intrinsics are used, on the platforms that support it.
 		/// Note that by enabling this you are changing the minspec for the PC platform, and the resultant executable will crash on machines without AVX support.
diff --git a/Engine/Source/Programs/UnrealBuildTool/Configuration/TargetRules.cs b/Engine/Source/Programs/UnrealBuildTool/Configuration/TargetRules.cs
index b3dac4efa6c..e0b6e130e9c 100644
--- a/Engine/Source/Programs/UnrealBuildTool/Configuration/TargetRules.cs
+++ b/Engine/Source/Programs/UnrealBuildTool/Configuration/TargetRules.cs
@@ -1083,6 +1083,13 @@ namespace UnrealBuildTool
 		[XmlConfigFile(Category = "BuildConfiguration")]
 		public bool bPGOOptimize = false;
 
+		/// <summary>
+		/// Whether the target requires code coverage compilation and linking.
+		/// </summary>
+		[CommandLine("-CodeCoverage", Value = "true")]
+		[XmlConfigFile(Category = "BuildConfiguration")]
+		public bool bCodeCoverage;
+
 		/// <summary>
 		/// Whether to support edit and continue.  Only works on Microsoft compilers.
 		/// </summary>
@@ -2493,6 +2500,11 @@ namespace UnrealBuildTool
 			get { return Inner.bPGOOptimize; }
 		}
 
+		public bool bCodeCoverage
+		{
+			get {return Inner.bCodeCoverage; }
+		}
+
 		public bool bSupportEditAndContinue
 		{
 			get { return Inner.bSupportEditAndContinue; }
diff --git a/Engine/Source/Programs/UnrealBuildTool/Configuration/UEBuildBinary.cs b/Engine/Source/Programs/UnrealBuildTool/Configuration/UEBuildBinary.cs
index 4809ab00135..ccdaa77f718 100644
--- a/Engine/Source/Programs/UnrealBuildTool/Configuration/UEBuildBinary.cs
+++ b/Engine/Source/Programs/UnrealBuildTool/Configuration/UEBuildBinary.cs
@@ -184,6 +184,7 @@ namespace UnrealBuildTool
 
 			// Setup linking environment.
 			LinkEnvironment BinaryLinkEnvironment = SetupBinaryLinkEnvironment(Target, ToolChain, LinkEnvironment, CompileEnvironment, SpecificFilesToCompile, WorkingSet, ExeDir, Graph);
+			BinaryLinkEnvironment.bCodeCoverage = CompileEnvironment.bCodeCoverage;
 
 			// If we're generating projects, we only need include paths and definitions, there is no need to run the linking logic.
 			if (ProjectFileGenerator.bGenerateProjectFiles)
@@ -231,6 +232,7 @@ namespace UnrealBuildTool
 				ConsoleAppLinkEvironment.bIsBuildingConsoleApplication = true;
 				ConsoleAppLinkEvironment.WindowsEntryPointOverride = "WinMainCRTStartup";		// For WinMain() instead of "main()" for Launch module
 				ConsoleAppLinkEvironment.OutputFilePaths = ConsoleAppLinkEvironment.OutputFilePaths.Select(Path => GetAdditionalConsoleAppPath(Path)).ToList();
+				ConsoleAppLinkEvironment.bCodeCoverage = CompileEnvironment.bCodeCoverage;
 
 				// Link the console app executable
 				FileItem[] ConsoleAppOutputFiles = ToolChain.LinkAllFiles(ConsoleAppLinkEvironment, false, Graph);
@@ -700,6 +702,7 @@ namespace UnrealBuildTool
 		private LinkEnvironment SetupBinaryLinkEnvironment(ReadOnlyTargetRules Target, UEToolChain ToolChain, LinkEnvironment LinkEnvironment, CppCompileEnvironment CompileEnvironment, List<FileReference> SpecificFilesToCompile, ISourceFileWorkingSet WorkingSet, DirectoryReference ExeDir, IActionGraphBuilder Graph)
 		{
 			LinkEnvironment BinaryLinkEnvironment = new LinkEnvironment(LinkEnvironment);
+			BinaryLinkEnvironment.bCodeCoverage = CompileEnvironment.bCodeCoverage;
 			HashSet<UEBuildModule> LinkEnvironmentVisitedModules = new HashSet<UEBuildModule>();
 			List<UEBuildBinary> BinaryDependencies = new List<UEBuildBinary>();
 
diff --git a/Engine/Source/Programs/UnrealBuildTool/Configuration/UEBuildModuleCPP.cs b/Engine/Source/Programs/UnrealBuildTool/Configuration/UEBuildModuleCPP.cs
index 481bb6db1f2..a1caeec2253 100644
--- a/Engine/Source/Programs/UnrealBuildTool/Configuration/UEBuildModuleCPP.cs
+++ b/Engine/Source/Programs/UnrealBuildTool/Configuration/UEBuildModuleCPP.cs
@@ -624,6 +624,7 @@ namespace UnrealBuildTool
 			CompileEnvironment.PrecompiledHeaderAction = PrecompiledHeaderAction.Create;
 			CompileEnvironment.PrecompiledHeaderIncludeFilename = WrapperFile.Location;
 			CompileEnvironment.bOptimizeCode = ModuleCompileEnvironment.bOptimizeCode;
+			CompileEnvironment.bCodeCoverage = ModuleCompileEnvironment.bCodeCoverage;
 
 			// Create the action to compile the PCH file.
 			CPPOutput Output;
@@ -822,6 +823,7 @@ namespace UnrealBuildTool
 		private void CopySettingsForSharedPCH(CppCompileEnvironment ModuleCompileEnvironment, CppCompileEnvironment CompileEnvironment)
 		{
 			CompileEnvironment.bOptimizeCode = ModuleCompileEnvironment.bOptimizeCode;
+			CompileEnvironment.bCodeCoverage = ModuleCompileEnvironment.bCodeCoverage;
 			CompileEnvironment.bUseRTTI = ModuleCompileEnvironment.bUseRTTI;
 			CompileEnvironment.bEnableExceptions = ModuleCompileEnvironment.bEnableExceptions;
 			CompileEnvironment.ShadowVariableWarningLevel = ModuleCompileEnvironment.ShadowVariableWarningLevel;
@@ -1238,9 +1240,13 @@ namespace UnrealBuildTool
 		/// <param name="Setting">The optimization setting from the rules file</param>
 		/// <param name="Configuration">The active target configuration</param>
 		/// <param name="bIsEngineModule">Whether the current module is an engine module</param>
+		/// <param name="bCodeCoverage">Whether the current module should be compiled with code coverage support</param>
 		/// <returns>True if optimization should be enabled</returns>
-		public static bool ShouldEnableOptimization(ModuleRules.CodeOptimization Setting, UnrealTargetConfiguration Configuration, bool bIsEngineModule)
+		public static bool ShouldEnableOptimization(ModuleRules.CodeOptimization Setting, UnrealTargetConfiguration Configuration, bool bIsEngineModule, bool bCodeCoverage)
 		{
+			if (bCodeCoverage) {
+				return false;
+			}
 			switch(Setting)
 			{
 				case ModuleRules.CodeOptimization.Never:
@@ -1275,7 +1281,8 @@ namespace UnrealBuildTool
 
 			// Override compile environment
 			Result.bUseUnity = Rules.bUseUnity;
-			Result.bOptimizeCode = ShouldEnableOptimization(Rules.OptimizeCode, Target.Configuration, Rules.bTreatAsEngineModule);
+			Result.bCodeCoverage = Target.bCodeCoverage; // From Target!
+			Result.bOptimizeCode = ShouldEnableOptimization(Rules.OptimizeCode, Target.Configuration, Rules.bTreatAsEngineModule, Result.bCodeCoverage);
 			Result.bUseRTTI |= Rules.bUseRTTI;
 			Result.bUseAVX = Rules.bUseAVX;
 			Result.bEnableBufferSecurityChecks = Rules.bEnableBufferSecurityChecks;
@@ -1348,8 +1355,9 @@ namespace UnrealBuildTool
 		{
 			CppCompileEnvironment CompileEnvironment = new CppCompileEnvironment(BaseCompileEnvironment);
 
-			// Use the default optimization setting for 
-			CompileEnvironment.bOptimizeCode = ShouldEnableOptimization(ModuleRules.CodeOptimization.Default, Target.Configuration, Rules.bTreatAsEngineModule);
+			// Use the default optimization setting for
+			CompileEnvironment.bOptimizeCode = ShouldEnableOptimization(ModuleRules.CodeOptimization.Default, Target.Configuration, Rules.bTreatAsEngineModule, Rules.bCodeCoverage);
+			CompileEnvironment.bCodeCoverage = Rules.bCodeCoverage;
 
 			// Override compile environment
 			CompileEnvironment.bIsBuildingDLL = !Target.ShouldCompileMonolithic();
diff --git a/Engine/Source/Programs/UnrealBuildTool/Configuration/UEBuildTarget.cs b/Engine/Source/Programs/UnrealBuildTool/Configuration/UEBuildTarget.cs
index 97a937d41af..2b401a4f326 100644
--- a/Engine/Source/Programs/UnrealBuildTool/Configuration/UEBuildTarget.cs
+++ b/Engine/Source/Programs/UnrealBuildTool/Configuration/UEBuildTarget.cs
@@ -3439,6 +3439,7 @@ namespace UnrealBuildTool
 			GlobalCompileEnvironment.bHideSymbolsByDefault = !Rules.bPublicSymbolsByDefault;
 			GlobalCompileEnvironment.CppStandard = Rules.CppStandard;
 			GlobalCompileEnvironment.AdditionalArguments = Rules.AdditionalCompilerArguments;
+			GlobalCompileEnvironment.bCodeCoverage = Rules.bCodeCoverage;
 
 			GlobalLinkEnvironment.bIsBuildingConsoleApplication = Rules.bIsBuildingConsoleApplication;
 			GlobalLinkEnvironment.bOptimizeForSize = Rules.bCompileForSize;
@@ -3456,6 +3457,7 @@ namespace UnrealBuildTool
 			GlobalLinkEnvironment.bUseFastPDBLinking = Rules.bUseFastPDBLinking ?? false;
 			GlobalLinkEnvironment.bPrintTimingInfo = Rules.bPrintToolChainTimingInfo;
 			GlobalLinkEnvironment.AdditionalArguments = Rules.AdditionalLinkerArguments;
+			GlobalLinkEnvironment.bCodeCoverage = Rules.bCodeCoverage;
 
 			if (Rules.bPGOOptimize && Rules.bPGOProfile)
 			{
diff --git a/Engine/Source/Programs/UnrealBuildTool/Platform/Linux/LinuxToolChain.cs b/Engine/Source/Programs/UnrealBuildTool/Platform/Linux/LinuxToolChain.cs
index fb38ffe34fe..ba6b28f48d0 100644
--- a/Engine/Source/Programs/UnrealBuildTool/Platform/Linux/LinuxToolChain.cs
+++ b/Engine/Source/Programs/UnrealBuildTool/Platform/Linux/LinuxToolChain.cs
@@ -170,6 +170,7 @@ namespace UnrealBuildTool
 				bIsCrossCompiling = true;
 
 				bHasValidCompiler = DetermineCompilerVersion();
+				CompilerRTPath = Path.Combine(Path.Combine(BaseLinuxPath, String.Format("lib/clang/{0}/lib/linux/", CompilerVersionString)));
 			}
 
 			if (!bHasValidCompiler)
@@ -767,8 +768,13 @@ namespace UnrealBuildTool
 				}
 			}
 
-			// optimization level
-			if (!CompileEnvironment.bOptimizeCode)
+			if (CompileEnvironment.bCodeCoverage)
+			{
+				Result += " -O0";
+				Result += " -fprofile-arcs -ftest-coverage"; // gcov
+				//Result += " -fprofile-instr-generate -fcoverage-mapping"; // llvm-cov
+			}
+			else if (!CompileEnvironment.bOptimizeCode) // optimization level
 			{
 				Result += " -O0";
 			}
@@ -1019,6 +1025,15 @@ namespace UnrealBuildTool
 				Result += " -Wl,--gdb-index";
 			}
 
+			if (LinkEnvironment.bCodeCoverage)
+			{
+				// Unreal Separates the linking phase and the compilation phase.
+				// We pass to clang the flag `--coverage` during the compile time
+				// And we link the correct compiler-rt library (shipped by UE, and part of the LLVM toolchain)
+				// to every binary produced.
+				Result += string.Format(" -L{0} -l{1}", CompilerRTPath, "clang_rt.profile-x86_64"); // gcov
+				// Result += " -fprofile-instr-generate"; // llvm-cov
+			}
 			// RPATH for third party libs
 			Result += " -Wl,-rpath=${ORIGIN}";
 			Result += " -Wl,-rpath-link=${ORIGIN}";
@@ -1142,6 +1157,7 @@ namespace UnrealBuildTool
 		protected string BaseLinuxPath;
 		protected string ClangPath;
 		protected string GCCPath;
+		protected string CompilerRTPath;
 		protected string ArPath;
 		protected string LlvmArPath;
 		protected string RanlibPath;
@@ -1270,6 +1286,11 @@ namespace UnrealBuildTool
 				Log.TraceInformation("  Prefix for PGO data files='{0}'", CompileEnvironment.PGOFilenamePrefix);
 			}
 
+			if (CompileEnvironment.bCodeCoverage)
+			{
+				Log.TraceInformation("Using --coverage build flag");
+			}
+
 			if (CompileEnvironment.bPGOProfile)
 			{
 				Log.TraceInformation("Using PGI (profile guided instrumentation).");
diff --git a/Engine/Source/Programs/UnrealBuildTool/Platform/Linux/UEBuildLinux.cs b/Engine/Source/Programs/UnrealBuildTool/Platform/Linux/UEBuildLinux.cs
index d8b35ac02ab..de3fc2d944e 100644
--- a/Engine/Source/Programs/UnrealBuildTool/Platform/Linux/UEBuildLinux.cs
+++ b/Engine/Source/Programs/UnrealBuildTool/Platform/Linux/UEBuildLinux.cs
@@ -526,6 +526,8 @@ namespace UnrealBuildTool
 				LinkEnvironment.PGOFilenamePrefix = CompileEnvironment.PGOFilenamePrefix;
 			}
 
+			LinkEnvironment.bCodeCoverage = CompileEnvironment.bCodeCoverage;
+
 			// For consistency with other platforms, also enable LTO whenever doing profile-guided optimizations.
 			// Obviously both PGI (instrumented) and PGO (optimized) binaries need to have that
 			if (CompileEnvironment.bPGOProfile || CompileEnvironment.bPGOOptimize)
diff --git a/Engine/Source/Programs/UnrealBuildTool/System/CppCompileEnvironment.cs b/Engine/Source/Programs/UnrealBuildTool/System/CppCompileEnvironment.cs
index 189954552a3..f56830c64d2 100644
--- a/Engine/Source/Programs/UnrealBuildTool/System/CppCompileEnvironment.cs
+++ b/Engine/Source/Programs/UnrealBuildTool/System/CppCompileEnvironment.cs
@@ -221,6 +221,11 @@ namespace UnrealBuildTool
 		/// </summary>
 		public bool bOptimizeCode = false;
 
+		/// <summary>
+		/// True if the compilation should produce tracing output for code coverage.
+		/// </summary>
+		public bool bCodeCoverage = false;
+
 		/// <summary>
 		/// Whether to optimize for minimal code size
 		/// </summary>
@@ -428,6 +433,7 @@ namespace UnrealBuildTool
 			bUndefinedIdentifierWarningsAsErrors = Other.bUndefinedIdentifierWarningsAsErrors;
 			bEnableUndefinedIdentifierWarnings = Other.bEnableUndefinedIdentifierWarnings;
 			bOptimizeCode = Other.bOptimizeCode;
+			bCodeCoverage = Other.bCodeCoverage;
 			bOptimizeForSize = Other.bOptimizeForSize;
 			bCreateDebugInfo = Other.bCreateDebugInfo;
 			bIsBuildingLibrary = Other.bIsBuildingLibrary;
diff --git a/Engine/Source/Programs/UnrealBuildTool/System/LinkEnvironment.cs b/Engine/Source/Programs/UnrealBuildTool/System/LinkEnvironment.cs
index 610e4b3db4d..9a94a6b4388 100644
--- a/Engine/Source/Programs/UnrealBuildTool/System/LinkEnvironment.cs
+++ b/Engine/Source/Programs/UnrealBuildTool/System/LinkEnvironment.cs
@@ -196,6 +196,11 @@ namespace UnrealBuildTool
 		/// </summary>
 		public bool bOptimizeForSize = false;
 
+		/// <summary>
+		/// Wether to link code coverage / tracing libs
+		/// </summary>
+		public bool bCodeCoverage = false;
+
 		/// <summary>
 		/// Whether to omit frame pointers or not. Disabling is useful for e.g. memory profiling on the PC
 		/// </summary>
@@ -349,6 +354,7 @@ namespace UnrealBuildTool
 			DefaultStackSize = Other.DefaultStackSize;
 			DefaultStackSizeCommit = Other.DefaultStackSizeCommit;
 			bOptimizeForSize = Other.bOptimizeForSize;
+			bCodeCoverage = Other.bCodeCoverage;
 			bOmitFramePointers = Other.bOmitFramePointers;
 			bSupportEditAndContinue = Other.bSupportEditAndContinue;
 			bUseIncrementalLinking = Other.bUseIncrementalLinking;

awesome, keep me posted!

Awesome work @galeone! Have you considered submitting this as a PR?

I did it, but I'm getting ignored lol EpicGames/UnrealEngine#9294

…

On Wed, Jul 20, 2022, 03:50 Sam Jeeves ***@***.***> wrote: ***@***.**** commented on this gist. ------------------------------ Awesome work @galeone <https://github.com/galeone>! Have you considered submitting this as a PR? — Reply to this email directly, view it on GitHub <https://gist.github.com/f8bdf0fb4fafc517a4f65537b2ae2634#gistcomment-4238767>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACAJSDCAW465ICYB5FNFIWTVU7KXTANCNFSM5S6A5SOQ> . You are receiving this because you were mentioned.Message ID: ***@***.***>

@galeone Really awesome to see this implemented in 5.3.0 as part of CL 25794147 and documented here: https://docs.unrealengine.com/5.3/en-US/static-code-analysis-in-unreal-engine/

@CanisHelix but these are the sanitizers, it's not the code coverage support

@galeone I will be testing shortly, but trying to apply the patch to 5.3.1, it looks like your changes are finally included in the Unreal release!