41 files changed, 1890 insertions, 392 deletions

diff --git a/src/burn/engine/approvedexe.cpp b/src/burn/engine/approvedexe.cpp
index 2a96868e..d8bd956b 100644
--- a/src/burn/engine/approvedexe.cpp
+++ b/src/burn/engine/approvedexe.cpp
@@ -148,6 +148,7 @@ extern "C" HRESULT ApprovedExesLaunch(
     LPWSTR sczCommand = NULL;
     LPWSTR sczCommandObfuscated = NULL;
     LPWSTR sczExecutableDirectory = NULL;
+    size_t cchExecutableDirectory = 0;
     STARTUPINFOW si = { };
     PROCESS_INFORMATION pi = { };
 
@@ -177,9 +178,17 @@ extern "C" HRESULT ApprovedExesLaunch(
     // Try to get the directory of the executable so we can set the current directory of the process to help those executables
     // that expect stuff to be relative to them.  Best effort only.
     hr = PathGetDirectory(pLaunchApprovedExe->sczExecutablePath, &sczExecutableDirectory);
+    if (SUCCEEDED(hr))
+    {
+        // CreateProcessW has undocumented MAX_PATH restriction for lpCurrentDirectory even when long path support is enabled.
+        hr = ::StringCchLengthW(sczExecutableDirectory, MAX_PATH - 1, &cchExecutableDirectory);
+    }
+
     if (FAILED(hr))
     {
         ReleaseNullStr(sczExecutableDirectory);
+
+        hr = S_OK;
     }
 
     LogId(REPORT_STANDARD, MSG_LAUNCHING_APPROVED_EXE, pLaunchApprovedExe->sczExecutablePath, sczCommandObfuscated);
diff --git a/src/burn/engine/cache.cpp b/src/burn/engine/cache.cpp
index cf9de1c3..eb5cc508 100644
--- a/src/burn/engine/cache.cpp
+++ b/src/burn/engine/cache.cpp
@@ -174,7 +174,7 @@ extern "C" HRESULT CacheInitialize(
 
     // Cache paths are initialized once so they cannot be changed while the engine is caching payloads.
     // Always construct the default machine package cache path so we can determine if we're redirected.
-    hr = PathGetKnownFolder(CSIDL_COMMON_APPDATA, &sczAppData);
+    hr = ShelGetFolder(&sczAppData, CSIDL_COMMON_APPDATA);
     ExitOnFailure(hr, "Failed to find local %hs appdata directory.", "per-machine");
 
     hr = PathConcat(sczAppData, PACKAGE_CACHE_FOLDER_NAME, &pCache->sczDefaultMachinePackageCache);
@@ -210,7 +210,7 @@ extern "C" HRESULT CacheInitialize(
     pCache->fCustomMachinePackageCache = !fPathEqual;
 
 
-    hr = PathGetKnownFolder(CSIDL_LOCAL_APPDATA, &sczAppData);
+    hr = ShelGetFolder(&sczAppData, CSIDL_LOCAL_APPDATA);
     ExitOnFailure(hr, "Failed to find local %hs appdata directory.", "per-user");
 
     hr = PathConcat(sczAppData, PACKAGE_CACHE_FOLDER_NAME, &pCache->sczDefaultUserPackageCache);
@@ -1469,7 +1469,7 @@ static HRESULT CalculateWorkingFolders(
     HRESULT hr = S_OK;
     LPWSTR sczBaseAcquisitionPath = NULL;
 
-    hr = PathGetTempPath(&sczBaseAcquisitionPath);
+    hr = PathGetTempPath(&sczBaseAcquisitionPath, NULL);
     ExitOnFailure(hr, "Failed to get temp folder path for acquisition folder base.");
 
     hr = PathBackslashTerminate(&sczBaseAcquisitionPath);
diff --git a/src/burn/engine/engine.cpp b/src/burn/engine/engine.cpp
index 7fca1141..13075497 100644
--- a/src/burn/engine/engine.cpp
+++ b/src/burn/engine/engine.cpp
@@ -486,7 +486,7 @@ static HRESULT RunUntrusted(
 
     si.cb = sizeof(si);
     si.wShowWindow = static_cast<WORD>(pEngineState->command.nCmdShow);
-    if (!::CreateProcessW(wzCleanRoomBundlePath, sczFullCommandLine, NULL, NULL, TRUE, 0, 0, NULL, &si, &pi))
+    if (!::CreateProcessW(wzCleanRoomBundlePath, sczFullCommandLine, NULL, NULL, TRUE, 0, NULL, NULL, &si, &pi))
     {
         ExitWithLastError(hr, "Failed to launch clean room process: %ls", sczFullCommandLine);
     }
diff --git a/src/burn/engine/exeengine.cpp b/src/burn/engine/exeengine.cpp
index f7be082d..701adb74 100644
--- a/src/burn/engine/exeengine.cpp
+++ b/src/burn/engine/exeengine.cpp
@@ -695,6 +695,7 @@ extern "C" HRESULT ExeEngineRunProcess(
     BOOL fDelayedCancel = FALSE;
     BOOL fFireAndForget = BURN_PACKAGE_TYPE_EXE == pPackage->type && pPackage->Exe.fFireAndForget;
     BOOL fInheritHandles = BURN_PACKAGE_TYPE_BUNDLE == pPackage->type;
+    size_t cchCachedDirectory = 0;
 
     // Always add user supplied arguments last.
     if (wzUserArgs)
@@ -703,6 +704,12 @@ extern "C" HRESULT ExeEngineRunProcess(
         ExitOnFailure(hr, "Failed to append user args.");
     }
 
+    // CreateProcessW has undocumented MAX_PATH restriction for lpCurrentDirectory even when long path support is enabled.
+    if (wzCachedDirectory && FAILED(::StringCchLengthW(wzCachedDirectory, MAX_PATH - 1, &cchCachedDirectory)))
+    {
+        wzCachedDirectory = NULL;
+    }
+
     // Make the cache location of the executable the current directory to help those executables
     // that expect stuff to be relative to them.
     si.cb = sizeof(si);
diff --git a/src/burn/engine/logging.cpp b/src/burn/engine/logging.cpp
index 1020d01f..68f0c35b 100644
--- a/src/burn/engine/logging.cpp
+++ b/src/burn/engine/logging.cpp
@@ -211,7 +211,7 @@ extern "C" void LoggingOpenFailed()
     LPCWSTR* lpStrings = const_cast<LPCWSTR*>(&LOG_FAILED_EVENT_LOG_MESSAGE);
     WORD wNumStrings = 1;
 
-    hr = LogOpen(NULL, L"Setup", L"_Failed", L"txt", FALSE, FALSE, NULL);
+    hr = LogOpen(NULL, L"Setup", L"_Failed", L"log", FALSE, FALSE, NULL);
     if (SUCCEEDED(hr))
     {
         ExitFunction();
@@ -965,19 +965,14 @@ static HRESULT GetNonSessionSpecificTempFolder(
     )
 {
     HRESULT hr = S_OK;
-    WCHAR wzTempFolder[MAX_PATH] = { };
+    LPWSTR sczTempFolder = NULL;
     SIZE_T cchTempFolder = 0;
     DWORD dwSessionId = 0;
     LPWSTR sczSessionId = 0;
     SIZE_T cchSessionId = 0;
 
-    if (!::GetTempPathW(countof(wzTempFolder), wzTempFolder))
-    {
-        ExitWithLastError(hr, "Failed to get temp folder.");
-    }
-
-    hr = ::StringCchLengthW(wzTempFolder, countof(wzTempFolder), reinterpret_cast<size_t*>(&cchTempFolder));
-    ExitOnFailure(hr, "Failed to get length of temp folder.");
+    hr = PathGetTempPath(&sczTempFolder, &cchTempFolder);
+    ExitOnFailure(hr, "Failed to get temp folder.");
 
     // If our session id is in the TEMP path then remove that part so we get the non-session
     // specific temporary folder.
@@ -989,17 +984,18 @@ static HRESULT GetNonSessionSpecificTempFolder(
         hr = ::StringCchLengthW(sczSessionId, STRSAFE_MAX_CCH, reinterpret_cast<size_t*>(&cchSessionId));
         ExitOnFailure(hr, "Failed to get length of session id string.");
 
-        if (CSTR_EQUAL == ::CompareStringW(LOCALE_NEUTRAL, 0, wzTempFolder + cchTempFolder - cchSessionId, static_cast<DWORD>(cchSessionId), sczSessionId, static_cast<DWORD>(cchSessionId)))
+        if (CSTR_EQUAL == ::CompareStringW(LOCALE_NEUTRAL, 0, sczTempFolder + cchTempFolder - cchSessionId, static_cast<DWORD>(cchSessionId), sczSessionId, static_cast<DWORD>(cchSessionId)))
         {
             cchTempFolder -= cchSessionId;
         }
     }
 
-    hr = StrAllocString(psczNonSessionTempFolder, wzTempFolder, cchTempFolder);
+    hr = StrAllocString(psczNonSessionTempFolder, sczTempFolder, cchTempFolder);
     ExitOnFailure(hr, "Failed to copy temp folder.");
 
 LExit:
     ReleaseStr(sczSessionId);
+    ReleaseStr(sczTempFolder);
 
     return hr;
 }
diff --git a/src/burn/engine/msuengine.cpp b/src/burn/engine/msuengine.cpp
index 1b051165..400fdc92 100644
--- a/src/burn/engine/msuengine.cpp
+++ b/src/burn/engine/msuengine.cpp
@@ -269,7 +269,6 @@ extern "C" HRESULT MsuEngineExecutePackage(
     HRESULT hr = S_OK;
     LPWSTR sczCachedDirectory = NULL;
     LPWSTR sczMsuPath = NULL;
-    LPWSTR sczWindowsPath = NULL;
     LPWSTR sczSystemPath = NULL;
     LPWSTR sczWusaPath = NULL;
     LPWSTR sczCommand = NULL;
@@ -294,15 +293,12 @@ extern "C" HRESULT MsuEngineExecutePackage(
     // get wusa.exe path
     if (fUseSysNativePath)
     {
-        hr = PathGetKnownFolder(CSIDL_WINDOWS, &sczWindowsPath);
-        ExitOnFailure(hr, "Failed to find Windows directory.");
-
-        hr = PathConcat(sczWindowsPath, L"SysNative\\", &sczSystemPath);
+        hr = PathSystemWindowsSubdirectory(L"SysNative\\", &sczSystemPath);
         ExitOnFailure(hr, "Failed to append SysNative directory.");
     }
     else
     {
-        hr = PathGetKnownFolder(CSIDL_SYSTEM, &sczSystemPath);
+        hr = PathGetSystemDirectory(&sczSystemPath);
         ExitOnFailure(hr, "Failed to find System32 directory.");
     }
 
@@ -390,7 +386,6 @@ LExit:
     ReleaseStr(sczCachedDirectory);
     ReleaseStr(sczMsuPath);
     ReleaseStr(sczSystemPath);
-    ReleaseStr(sczWindowsPath);
     ReleaseStr(sczWusaPath);
     ReleaseStr(sczCommand);
     ReleaseStr(sczEscapedKB);
diff --git a/src/burn/engine/userexperience.cpp b/src/burn/engine/userexperience.cpp
index a97234ef..6f84caba 100644
--- a/src/burn/engine/userexperience.cpp
+++ b/src/burn/engine/userexperience.cpp
@@ -99,6 +99,7 @@ extern "C" HRESULT UserExperienceLoad(
     HRESULT hr = S_OK;
     BOOTSTRAPPER_CREATE_ARGS args = { };
     BOOTSTRAPPER_CREATE_RESULTS results = { };
+    LPCWSTR wzPath = pUserExperience->payloads.rgPayloads[0].sczLocalFilePath;
 
     args.cbSize = sizeof(BOOTSTRAPPER_CREATE_ARGS);
     args.pCommand = pCommand;
@@ -109,8 +110,8 @@ extern "C" HRESULT UserExperienceLoad(
     results.cbSize = sizeof(BOOTSTRAPPER_CREATE_RESULTS);
 
     // Load BA DLL.
-    pUserExperience->hUXModule = ::LoadLibraryExW(pUserExperience->payloads.rgPayloads[0].sczLocalFilePath, NULL, LOAD_WITH_ALTERED_SEARCH_PATH);
-    ExitOnNullWithLastError(pUserExperience->hUXModule, hr, "Failed to load BA DLL.");
+    pUserExperience->hUXModule = ::LoadLibraryExW(wzPath, NULL, LOAD_WITH_ALTERED_SEARCH_PATH);
+    ExitOnNullWithLastError(pUserExperience->hUXModule, hr, "Failed to load BA DLL: %ls", wzPath);
 
     // Get BootstrapperApplicationCreate entry-point.
     PFN_BOOTSTRAPPER_APPLICATION_CREATE pfnCreate = (PFN_BOOTSTRAPPER_APPLICATION_CREATE)::GetProcAddress(pUserExperience->hUXModule, "BootstrapperApplicationCreate");
diff --git a/src/burn/engine/variable.cpp b/src/burn/engine/variable.cpp
index c96e9d95..8d208a66 100644
--- a/src/burn/engine/variable.cpp
+++ b/src/burn/engine/variable.cpp
@@ -1947,18 +1947,18 @@ static HRESULT InitializeVariableTempFolder(
     UNREFERENCED_PARAMETER(dwpData);
 
     HRESULT hr = S_OK;
-    WCHAR wzPath[MAX_PATH] = { };
+    LPWSTR sczPath = NULL;
 
-    if (!::GetTempPathW(MAX_PATH, wzPath))
-    {
-        ExitWithLastError(hr, "Failed to get temp path.");
-    }
+    hr = PathGetTempPath(&sczPath, NULL);
+    ExitOnFailure(hr, "Failed to get temp path.");
 
     // set value
-    hr = BVariantSetString(pValue, wzPath, 0, FALSE);
+    hr = BVariantSetString(pValue, sczPath, 0, FALSE);
     ExitOnFailure(hr, "Failed to set variant value.");
 
 LExit:
+    ReleaseStr(sczPath);
+
     return hr;
 }
 
@@ -1969,7 +1969,7 @@ static HRESULT InitializeVariableSystemFolder(
 {
     HRESULT hr = S_OK;
     BOOL f64 = (BOOL)dwpData;
-    WCHAR wzSystemFolder[MAX_PATH + 2] = { };
+    LPWSTR sczSystemFolder = NULL;
 
 #if !defined(_WIN64)
     BOOL fIsWow64 = FALSE;
@@ -1979,57 +1979,43 @@ static HRESULT InitializeVariableSystemFolder(
     {
         if (f64)
         {
-            if (!::GetSystemDirectoryW(wzSystemFolder, countof(wzSystemFolder)))
-            {
-                ExitWithLastError(hr, "Failed to get 64-bit system folder.");
-            }
+            hr = PathGetSystemDirectory(&sczSystemFolder);
+            ExitOnFailure(hr, "Failed to get 64-bit system folder.");
         }
         else
         {
-            if (!::GetSystemWow64DirectoryW(wzSystemFolder, countof(wzSystemFolder)))
-            {
-                ExitWithLastError(hr, "Failed to get 32-bit system folder.");
-            }
+            hr = PathGetSystemWow64Directory(&sczSystemFolder);
+            ExitOnFailure(hr, "Failed to get 32-bit system folder.");
         }
     }
     else
     {
         if (!f64)
         {
-            if (!::GetSystemDirectoryW(wzSystemFolder, countof(wzSystemFolder)))
-            {
-                ExitWithLastError(hr, "Failed to get 32-bit system folder.");
-            }
+            hr = PathGetSystemDirectory(&sczSystemFolder);
+            ExitOnFailure(hr, "Failed to get 32-bit system folder.");
         }
     }
 #else
     if (f64)
     {
-        if (!::GetSystemDirectoryW(wzSystemFolder, countof(wzSystemFolder)))
-        {
-            ExitWithLastError(hr, "Failed to get 64-bit system folder.");
-        }
+        hr = PathGetSystemDirectory(&sczSystemFolder);
+        ExitOnFailure(hr, "Failed to get 64-bit system folder.");
     }
     else
     {
-        if (!::GetSystemWow64DirectoryW(wzSystemFolder, countof(wzSystemFolder)))
-        {
-            ExitWithLastError(hr, "Failed to get 32-bit system folder.");
-        }
+        hr = PathGetSystemWow64Directory(&sczSystemFolder);
+        ExitOnFailure(hr, "Failed to get 32-bit system folder.");
     }
 #endif
 
-    if (*wzSystemFolder)
-    {
-        hr = PathFixedBackslashTerminate(wzSystemFolder, countof(wzSystemFolder));
-        ExitOnFailure(hr, "Failed to backslash terminate system folder.");
-    }
-
     // set value
-    hr = BVariantSetString(pValue, wzSystemFolder, 0, FALSE);
+    hr = BVariantSetString(pValue, sczSystemFolder, 0, FALSE);
     ExitOnFailure(hr, "Failed to set system folder variant value.");
 
 LExit:
+    ReleaseStr(sczSystemFolder);
+
     return hr;
 }
 
@@ -2041,26 +2027,25 @@ static HRESULT InitializeVariableWindowsVolumeFolder(
     UNREFERENCED_PARAMETER(dwpData);
 
     HRESULT hr = S_OK;
-    WCHAR wzWindowsPath[MAX_PATH] = { };
-    WCHAR wzVolumePath[MAX_PATH] = { };
+    LPWSTR sczWindowsPath = NULL;
+    LPWSTR sczVolumePath = NULL;
 
     // get windows directory
-    if (!::GetWindowsDirectoryW(wzWindowsPath, countof(wzWindowsPath)))
-    {
-        ExitWithLastError(hr, "Failed to get windows directory.");
-    }
+    hr = PathSystemWindowsSubdirectory(NULL, &sczWindowsPath);
+    ExitOnFailure(hr, "Failed to get windows directory.");
 
     // get volume path name
-    if (!::GetVolumePathNameW(wzWindowsPath, wzVolumePath, MAX_PATH))
-    {
-        ExitWithLastError(hr, "Failed to get volume path name.");
-    }
+    hr = PathGetVolumePathName(sczWindowsPath, &sczVolumePath);
+    ExitOnFailure(hr, "Failed to get volume path name.");
 
     // set value
-    hr = BVariantSetString(pValue, wzVolumePath, 0, FALSE);
+    hr = BVariantSetString(pValue, sczVolumePath, 0, FALSE);
     ExitOnFailure(hr, "Failed to set variant value.");
 
 LExit:
+    ReleaseStr(sczWindowsPath);
+    ReleaseStr(sczVolumePath);
+
     return hr;
 }
 
diff --git a/src/burn/test/BurnUnitTest/RegistrationTest.cpp b/src/burn/test/BurnUnitTest/RegistrationTest.cpp
index 883b9cc8..aa3bd34b 100644
--- a/src/burn/test/BurnUnitTest/RegistrationTest.cpp
+++ b/src/burn/test/BurnUnitTest/RegistrationTest.cpp
@@ -108,8 +108,8 @@ namespace Bootstrapper
                 TestThrowOnFailure(hr, L"Failed to register bundle.");
 
                 // verify that registration was created
-                Assert::True(Directory::Exists(cacheDirectory));
-                Assert::True(File::Exists(Path::Combine(cacheDirectory, gcnew String(L"setup.exe"))));
+                Assert::True(Directory::Exists(cacheDirectory), "Cache directory didn't exist.");
+                Assert::True(File::Exists(Path::Combine(cacheDirectory, gcnew String(L"setup.exe"))), "Bundle exe wasn't cached.");
 
                 this->ValidateUninstallKeyResume(Int32(BURN_RESUME_MODE_ACTIVE));
                 this->ValidateRunOnceKeyEntry(cacheExePath);
@@ -119,7 +119,7 @@ namespace Bootstrapper
                 TestThrowOnFailure(hr, L"Failed to unregister bundle.");
 
                 // verify that registration was removed
-                Assert::False(Directory::Exists(cacheDirectory));
+                Assert::False(Directory::Exists(cacheDirectory), "Cache directory wasn't removed.");
 
                 this->ValidateUninstallKeyNull(L"Resume");
                 this->ValidateRunOnceKeyString(TEST_BUNDLE_ID, nullptr);
diff --git a/src/internal/WixBuildTools.TestSupport/ExternalExecutable.cs b/src/internal/WixBuildTools.TestSupport/ExternalExecutable.cs
index eb07aa13..4a932645 100644
--- a/src/internal/WixBuildTools.TestSupport/ExternalExecutable.cs
+++ b/src/internal/WixBuildTools.TestSupport/ExternalExecutable.cs
@@ -2,11 +2,16 @@
 
 namespace WixBuildTools.TestSupport
 {
+    using System;
     using System.Collections.Concurrent;
     using System.Collections.Generic;
+    using System.ComponentModel;
     using System.Diagnostics;
     using System.IO;
+    using System.Runtime.InteropServices;
     using System.Text;
+    using System.Threading.Tasks;
+    using Microsoft.Win32.SafeHandles;
 
     public abstract class ExternalExecutable
     {
@@ -19,6 +24,125 @@ namespace WixBuildTools.TestSupport
 
         protected ExternalExecutableResult Run(string args, bool mergeErrorIntoOutput = false, string workingDirectory = null)
         {
+            // https://github.com/dotnet/runtime/issues/58492
+            // Process.Start doesn't currently support starting a process with a long path,
+            // but the way to support long paths doesn't support searching for the executable if it was a relative path.
+            // Avoid the managed way of doing this even if the target isn't a long path to help verify that the native way works.
+            if (!Path.IsPathRooted(this.exePath))
+            {
+                return this.RunManaged(args, mergeErrorIntoOutput, workingDirectory);
+            }
+
+            // https://web.archive.org/web/20150331190801/https://support.microsoft.com/en-us/kb/190351
+            var commandLine = $"\"{this.exePath}\" {args}";
+            var currentDirectory = workingDirectory ?? Path.GetDirectoryName(this.exePath);
+            if (String.IsNullOrEmpty(currentDirectory))
+            {
+                currentDirectory = null;
+            }
+            var processInfo = new PROCESS_INFORMATION();
+            var startInfo = new STARTUPINFOW
+            {
+                cb = Marshal.SizeOf(typeof(STARTUPINFOW)),
+                dwFlags = StartupInfoFlags.STARTF_FORCEOFFFEEDBACK | StartupInfoFlags.STARTF_USESTDHANDLES,
+                hStdInput = GetStdHandle(StdHandleType.STD_INPUT_HANDLE),
+            };
+            SafeFileHandle hStdOutputParent = null;
+            SafeFileHandle hStdErrorParent = null;
+
+            try
+            {
+                CreatePipeForProcess(out hStdOutputParent, out startInfo.hStdOutput);
+
+                if (!mergeErrorIntoOutput)
+                {
+                    CreatePipeForProcess(out hStdErrorParent, out startInfo.hStdError);
+                }
+                else
+                {
+                    if (!DuplicateHandle(GetCurrentProcess(), startInfo.hStdOutput, GetCurrentProcess(), out startInfo.hStdError, 0, true, DuplicateHandleOptions.DUPLICATE_SAME_ACCESS))
+                    {
+                        throw new Win32Exception();
+                    }
+                }
+
+                if (!CreateProcessW(this.exePath, commandLine, IntPtr.Zero, IntPtr.Zero, true, CreateProcessFlags.CREATE_NO_WINDOW, IntPtr.Zero,
+                                    currentDirectory, ref startInfo, ref processInfo))
+                {
+                    throw new Win32Exception();
+                }
+
+                startInfo.Dispose();
+
+                return GetResultFromNative(mergeErrorIntoOutput, hStdOutputParent, hStdErrorParent, processInfo.hProcess, this.exePath, args);
+            }
+            finally
+            {
+                hStdErrorParent?.Dispose();
+                hStdOutputParent?.Dispose();
+
+                startInfo.Dispose();
+                processInfo.Dispose();
+            }
+        }
+
+        private static ExternalExecutableResult GetResultFromNative(bool mergeErrorIntoOutput, SafeFileHandle hStdOutputParent, SafeFileHandle hStdErrorParent, IntPtr hProcess, string fileName, string args)
+        {
+            using (var outputStream = new StreamReader(new FileStream(hStdOutputParent, FileAccess.Read)))
+            using (var errorStream = mergeErrorIntoOutput ? null : new StreamReader(new FileStream(hStdErrorParent, FileAccess.Read)))
+            {
+                var outputTask = Task.Run(() => ReadProcessStreamLines(outputStream));
+                var errorTask = Task.Run(() => ReadProcessStreamLines(errorStream));
+
+                while (!outputTask.Wait(100) || !errorTask.Wait(100)) { Task.Yield(); }
+                var standardOutput = outputTask.Result;
+                var standardError = errorTask.Result;
+
+                if (WaitForSingleObject(hProcess, -1) != 0)
+                {
+                    throw new Win32Exception();
+                }
+
+                if (!GetExitCodeProcess(hProcess, out var exitCode))
+                {
+                    throw new Win32Exception();
+                }
+
+                return new ExternalExecutableResult
+                {
+                    ExitCode = exitCode,
+                    StandardError = standardError,
+                    StandardOutput = standardOutput,
+                    FileName = fileName,
+                    Arguments = args,
+                };
+            }
+        }
+
+        private static string[] ReadProcessStreamLines(StreamReader streamReader)
+        {
+            if (streamReader == null)
+            {
+                return null;
+            }
+
+            var lines = new List<string>();
+            while (true)
+            {
+                var line = streamReader.ReadLine();
+                if (line == null)
+                {
+                    break;
+                }
+
+                lines.Add(line);
+            }
+
+            return lines.ToArray();
+        }
+
+        protected ExternalExecutableResult RunManaged(string args, bool mergeErrorIntoOutput = false, string workingDirectory = null)
+        {
             var startInfo = new ProcessStartInfo(this.exePath, args)
             {
                 CreateNoWindow = true,
@@ -48,7 +172,8 @@ namespace WixBuildTools.TestSupport
                     ExitCode = process.ExitCode,
                     StandardError = mergeErrorIntoOutput ? null : standardError.ToArray(),
                     StandardOutput = standardOutput.ToArray(),
-                    StartInfo = startInfo,
+                    FileName = this.exePath,
+                    Arguments = args,
                 };
             }
         }
@@ -84,5 +209,166 @@ namespace WixBuildTools.TestSupport
 
             return sb.ToString();
         }
+
+        private static void CreatePipeForProcess(out SafeFileHandle hReadPipe, out IntPtr hWritePipe)
+        {
+            var securityAttributes = new SECURITY_ATTRIBUTES
+            {
+                nLength = Marshal.SizeOf(typeof(SECURITY_ATTRIBUTES)),
+                bInheritHandle = true,
+            };
+
+            if (!CreatePipe(out var hReadTemp, out hWritePipe, ref securityAttributes, 0))
+            {
+                throw new Win32Exception();
+            }
+
+            // Only the handle passed to the process should be inheritable, so have to duplicate the other handle to get an uninheritable one.
+            if (!DuplicateHandle(GetCurrentProcess(), hReadTemp, GetCurrentProcess(), out var hReadPipePtr, 0, false, DuplicateHandleOptions.DUPLICATE_CLOSE_SOURCE | DuplicateHandleOptions.DUPLICATE_SAME_ACCESS))
+            {
+                throw new Win32Exception();
+            }
+
+            hReadPipe = new SafeFileHandle(hReadPipePtr, true);
+        }
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode, ExactSpelling = true, SetLastError = true)]
+        private extern static IntPtr GetStdHandle(StdHandleType nStdHandle);
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode, ExactSpelling = true, SetLastError = true)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private extern static bool CreatePipe(out IntPtr hReadPipe, out IntPtr hWritePipe, ref SECURITY_ATTRIBUTES lpPipeAttributes, int nSize);
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode, ExactSpelling = true, SetLastError = true)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private extern static bool CreateProcessW(
+            string lpApplicationName,
+            string lpCommandLine,
+            IntPtr lpProcessAttributes,
+            IntPtr lpThreadAttributes,
+            [MarshalAs(UnmanagedType.Bool)] bool bInheritHandles,
+            CreateProcessFlags dwCreationFlags,
+            IntPtr lpEnvironment,
+            string lpCurrentDirectory,
+            ref STARTUPINFOW lpStartupInfo,
+            ref PROCESS_INFORMATION lpProcessInformation);
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode, ExactSpelling = true)]
+        private extern static IntPtr GetCurrentProcess();
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode, ExactSpelling = true, SetLastError = true)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private extern static bool GetExitCodeProcess(IntPtr hHandle, out int lpExitCode);
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode, ExactSpelling = true, SetLastError = true)]
+        private extern static int WaitForSingleObject(IntPtr hHandle, int dwMilliseconds);
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode, ExactSpelling = true, SetLastError = true)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private extern static bool CloseHandle(IntPtr hObject);
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode, ExactSpelling = true, SetLastError = true)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private extern static bool DuplicateHandle(IntPtr hSourceProcessHandle, IntPtr hSourceHandle, IntPtr hTargetProcessHandle, out IntPtr lpTargetHandle, int dwDesiredAccess, [MarshalAs(UnmanagedType.Bool)] bool bInheritHandle, DuplicateHandleOptions dwOptions);
+
+        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+        private struct SECURITY_ATTRIBUTES
+        {
+            public int nLength;
+            public IntPtr lpSecurityDescriptor;
+            [MarshalAs(UnmanagedType.Bool)]
+            public bool bInheritHandle;
+        }
+
+        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+        private struct STARTUPINFOW
+        {
+            public int cb;
+            public string lpReserved;
+            public string lpDesktop;
+            public string lpTitle;
+            public int dwX;
+            public int dwY;
+            public int dwXSize;
+            public int dwYSize;
+            public int dwXCountChars;
+            public int dwYCountChars;
+            public int dwFillAttribute;
+            public StartupInfoFlags dwFlags;
+            public short wShowWindow;
+            public short cbReserved2;
+            public IntPtr lpReserved2;
+            public IntPtr hStdInput;
+            public IntPtr hStdOutput;
+            public IntPtr hStdError;
+
+            public void Dispose()
+            {
+                // This makes assumptions based on how it's used above.
+                if (this.hStdError != IntPtr.Zero)
+                {
+                    CloseHandle(this.hStdError);
+                    this.hStdError = IntPtr.Zero;
+                }
+
+                if (this.hStdOutput != IntPtr.Zero)
+                {
+                    CloseHandle(this.hStdOutput);
+                    this.hStdOutput = IntPtr.Zero;
+                }
+            }
+        }
+
+        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+        private struct PROCESS_INFORMATION
+        {
+            public IntPtr hProcess;
+            public IntPtr hThread;
+            public int dwProcessId;
+            public int dwThreadId;
+
+            public void Dispose()
+            {
+                if (this.hProcess != IntPtr.Zero)
+                {
+                    CloseHandle(this.hProcess);
+                    this.hProcess = IntPtr.Zero;
+                }
+
+                if (this.hThread != IntPtr.Zero)
+                {
+                    CloseHandle(this.hThread);
+                    this.hThread = IntPtr.Zero;
+                }
+            }
+        }
+
+        private enum StdHandleType
+        {
+            STD_INPUT_HANDLE = -10,
+            STD_OUTPUT_HANDLE = -11,
+            STD_ERROR_HANDLE = -12,
+        }
+
+        [Flags]
+        private enum CreateProcessFlags
+        {
+            None = 0x0,
+            CREATE_NO_WINDOW = 0x08000000,
+        }
+
+        [Flags]
+        private enum StartupInfoFlags
+        {
+            None = 0x0,
+            STARTF_FORCEOFFFEEDBACK = 0x80,
+            STARTF_USESTDHANDLES = 0x100,
+        }
+
+        private enum DuplicateHandleOptions
+        {
+            DUPLICATE_CLOSE_SOURCE = 1,
+            DUPLICATE_SAME_ACCESS = 2,
+        }
     }
 }
diff --git a/src/internal/WixBuildTools.TestSupport/ExternalExecutableResult.cs b/src/internal/WixBuildTools.TestSupport/ExternalExecutableResult.cs
index 19b5183b..950ee4bd 100644
--- a/src/internal/WixBuildTools.TestSupport/ExternalExecutableResult.cs
+++ b/src/internal/WixBuildTools.TestSupport/ExternalExecutableResult.cs
@@ -12,6 +12,8 @@ namespace WixBuildTools.TestSupport
 
         public string[] StandardOutput { get; set; }
 
-        public ProcessStartInfo StartInfo { get; set; }
+        public string FileName { get; set; }
+
+        public string Arguments { get; set; }
     }
 }
diff --git a/src/internal/WixBuildTools.TestSupport/TestDataFolderFileSystem.cs b/src/internal/WixBuildTools.TestSupport/TestDataFolderFileSystem.cs
index 8d670bf0..15b7631d 100644
--- a/src/internal/WixBuildTools.TestSupport/TestDataFolderFileSystem.cs
+++ b/src/internal/WixBuildTools.TestSupport/TestDataFolderFileSystem.cs
@@ -33,7 +33,7 @@ namespace WixBuildTools.TestSupport
             RobocopyFolder(sourceDirectoryPath, this.BaseFolder);
         }
 
-        private static ExternalExecutableResult RobocopyFolder(string sourceFolderPath, string destinationFolderPath)
+        public static ExternalExecutableResult RobocopyFolder(string sourceFolderPath, string destinationFolderPath)
         {
             var args = $"\"{sourceFolderPath}\" \"{destinationFolderPath}\" /E /R:1 /W:1";
             return RobocopyRunner.Execute(args);
diff --git a/src/libs/dutil/WixToolset.DUtil/apputil.cpp b/src/libs/dutil/WixToolset.DUtil/apputil.cpp
index b70c8cfb..9e75082a 100644
--- a/src/libs/dutil/WixToolset.DUtil/apputil.cpp
+++ b/src/libs/dutil/WixToolset.DUtil/apputil.cpp
@@ -87,31 +87,27 @@ DAPI_(HRESULT) LoadSystemLibraryWithPath(
     )
 {
     HRESULT hr = S_OK;
-    DWORD cch = 0;
-    WCHAR wzPath[MAX_PATH] = { };
+    LPWSTR sczDirectory = NULL;
+    LPWSTR sczPath = NULL;
 
-    cch = ::GetSystemDirectoryW(wzPath, MAX_PATH);
-    AppExitOnNullWithLastError(cch, hr, "Failed to get the Windows system directory.");
+    hr = PathGetSystemDirectory(&sczDirectory);
+    AppExitOnFailure(hr, "Failed to get the Windows system directory.");
 
-    if (L'\\' != wzPath[cch - 1])
-    {
-        hr = ::StringCchCatNW(wzPath, MAX_PATH, L"\\", 1);
-        AppExitOnRootFailure(hr, "Failed to terminate the string with a backslash.");
-    }
+    hr = StrAllocFormatted(&sczPath, L"%ls%ls", sczDirectory, wzModuleName);
+    AppExitOnFailure(hr, "Failed to create the fully-qualified path to %ls.", wzModuleName);
 
-    hr = ::StringCchCatW(wzPath, MAX_PATH, wzModuleName);
-    AppExitOnRootFailure(hr, "Failed to create the fully-qualified path to %ls.", wzModuleName);
-
-    *phModule = ::LoadLibraryExW(wzPath, NULL, LOAD_WITH_ALTERED_SEARCH_PATH);
-    AppExitOnNullWithLastError(*phModule, hr, "Failed to load the library %ls.", wzModuleName);
+    *phModule = ::LoadLibraryExW(sczPath, NULL, LOAD_WITH_ALTERED_SEARCH_PATH);
+    AppExitOnNullWithLastError(*phModule, hr, "Failed to load the library %ls.", sczPath);
 
     if (psczPath)
     {
-        hr = StrAllocString(psczPath, wzPath, MAX_PATH);
-        AppExitOnFailure(hr, "Failed to copy the path to library.");
+        *psczPath = sczPath;
+        sczPath = NULL;
     }
 
 LExit:
+    ReleaseStr(sczDirectory);
+
     return hr;
 }
 
diff --git a/src/libs/dutil/WixToolset.DUtil/cabcutil.cpp b/src/libs/dutil/WixToolset.DUtil/cabcutil.cpp
index d1edc54d..294669af 100644
--- a/src/libs/dutil/WixToolset.DUtil/cabcutil.cpp
+++ b/src/libs/dutil/WixToolset.DUtil/cabcutil.cpp
@@ -89,8 +89,8 @@ struct CABC_DATA
 
     STRINGDICT_HANDLE shDictHandle;
 
-    WCHAR wzCabinetPath[MAX_PATH];
-    WCHAR wzEmptyFile[MAX_PATH];
+    LPWSTR sczCabinetPath;
+    LPWSTR sczEmptyFile;
     HANDLE hEmptyFile;
     DWORD dwLastFileIndex;
 
@@ -197,33 +197,17 @@ extern "C" HRESULT DAPI CabCBegin(
 
     HRESULT hr = S_OK;
     CABC_DATA *pcd = NULL;
-    WCHAR wzTempPath[MAX_PATH] = { };
 
     C_ASSERT(sizeof(MSIFILEHASHINFO) == 20);
 
-    WCHAR wzPathBuffer [MAX_PATH] = L"";
-    size_t cchPathBuffer;
+    LPWSTR pwzPathBuffer = NULL;
     if (wzCabDir)
     {
-        hr = ::StringCchLengthW(wzCabDir, MAX_PATH, &cchPathBuffer);
-        CabcExitOnFailure(hr, "Failed to get length of cab directory");
-
-        // Need room to terminate with L'\\' and L'\0'
-        if((MAX_PATH - 1) <= cchPathBuffer || 0 == cchPathBuffer)
-        {
-            hr = E_INVALIDARG;
-            CabcExitOnFailure(hr, "Cab directory had invalid length: %u", cchPathBuffer);
-        }
-
-        hr = ::StringCchCopyW(wzPathBuffer, countof(wzPathBuffer), wzCabDir);
+        hr = StrAllocString(&pwzPathBuffer, wzCabDir, 0);
         CabcExitOnFailure(hr, "Failed to copy cab directory to buffer");
 
-        if (L'\\' != wzPathBuffer[cchPathBuffer - 1])
-        {
-            hr = ::StringCchCatW(wzPathBuffer, countof(wzPathBuffer), L"\\");
-            CabcExitOnFailure(hr, "Failed to cat \\ to end of buffer");
-            ++cchPathBuffer;
-        }
+        hr = PathBackslashTerminate(&pwzPathBuffer);
+        CabcExitOnFailure(hr, "Failed to cat \\ to end of buffer");
     }
 
     pcd = static_cast<CABC_DATA*>(MemAlloc(sizeof(CABC_DATA), TRUE));
@@ -290,33 +274,23 @@ extern "C" HRESULT DAPI CabCBegin(
         CabcExitWithLastError(hr, "failed to convert cab name to multi-byte");
     }
 
-    if (0 ==  ::WideCharToMultiByte(CP_ACP, WC_NO_BEST_FIT_CHARS, wzPathBuffer, -1, pcd->ccab.szCabPath, sizeof(pcd->ccab.szCab), NULL, NULL))
+    if (0 == ::WideCharToMultiByte(CP_ACP, WC_NO_BEST_FIT_CHARS, pwzPathBuffer, -1, pcd->ccab.szCabPath, sizeof(pcd->ccab.szCab), NULL, NULL))
     {
         CabcExitWithLastError(hr, "failed to convert cab dir to multi-byte");
     }
 
     // Remember the path to the cabinet.
-    hr= ::StringCchCopyW(pcd->wzCabinetPath, countof(pcd->wzCabinetPath), wzPathBuffer);
-    CabcExitOnFailure(hr, "Failed to copy cabinet path from path: %ls", wzPathBuffer);
-
-    hr = ::StringCchCatW(pcd->wzCabinetPath, countof(pcd->wzCabinetPath), wzCab);
+    hr = PathConcat(pwzPathBuffer, wzCab, &pcd->sczCabinetPath);
     CabcExitOnFailure(hr, "Failed to concat to cabinet path cabinet name: %ls", wzCab);
 
     // Get the empty file to use as the blank marker for duplicates.
-    if (!::GetTempPathW(countof(wzTempPath), wzTempPath))
-    {
-        CabcExitWithLastError(hr, "Failed to get temp path.");
-    }
-
-    if (!::GetTempFileNameW(wzTempPath, L"WSC", 0, pcd->wzEmptyFile))
-    {
-        CabcExitWithLastError(hr, "Failed to create a temp file name.");
-    }
+    hr = DirCreateTempPath(L"WSC", &pcd->sczEmptyFile);
+    CabcExitOnFailure(hr, "Failed to create a temp file name.");
 
     // Try to open the newly created empty file (remember, GetTempFileName() is kind enough to create a file for us)
     // with a handle to automatically delete the file on close. Ignore any failure that might happen, since the worst
     // case is we'll leave a zero byte file behind in the temp folder.
-    pcd->hEmptyFile = ::CreateFileW(pcd->wzEmptyFile, 0, FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_TEMPORARY | FILE_FLAG_DELETE_ON_CLOSE, NULL);
+    pcd->hEmptyFile = ::CreateFileW(pcd->sczEmptyFile, 0, FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_TEMPORARY | FILE_FLAG_DELETE_ON_CLOSE, NULL);
 
     hr = DictCreateWithEmbeddedKey(&pcd->shDictHandle, dwMaxFiles, reinterpret_cast<void **>(&pcd->prgFiles), offsetof(CABC_FILE, pwzSourcePath), DICT_FLAG_CASEINSENSITIVE);
     CabcExitOnFailure(hr, "Failed to create dictionary to keep track of duplicate files");
@@ -358,6 +332,8 @@ extern "C" HRESULT DAPI CabCBegin(
     *phContext = pcd;
 
 LExit:
+    ReleaseStr(pwzPathBuffer);
+
     if (FAILED(hr) && pcd && pcd->hfci)
     {
         ::FCIDestroy(pcd->hfci);
@@ -527,7 +503,7 @@ extern "C" HRESULT DAPI CabCFinish(
             // files point at the same path (the empty file) so there is no point in tracking them with
             // their path.
             fileInfo.wzSourcePath = pcd->prgDuplicates[dwDupeArrayFileIndex].pwzSourcePath;
-            fileInfo.wzEmptyPath = pcd->wzEmptyFile;
+            fileInfo.wzEmptyPath = pcd->sczEmptyFile;
 
             // Use the provided token, otherwise default to the source file name.
             if (pcd->prgDuplicates[dwDupeArrayFileIndex].pwzToken)
@@ -643,7 +619,7 @@ extern "C" HRESULT DAPI CabCFinish(
     if (pcd->fGoodCab && pcd->cDuplicates)
     {
         hr = UpdateDuplicateFiles(pcd);
-        CabcExitOnFailure(hr, "Failed to update duplicates in cabinet: %ls", pcd->wzCabinetPath);
+        CabcExitOnFailure(hr, "Failed to update duplicates in cabinet: %ls", pcd->sczCabinetPath);
     }
 
 LExit:
@@ -692,6 +668,9 @@ static void FreeCabCData(
         ReleaseMem(pcd->prgFiles);
         ReleaseMem(pcd->prgDuplicates);
 
+        ReleaseStr(pcd->sczCabinetPath);
+        ReleaseStr(pcd->sczEmptyFile);
+
         ReleaseMem(pcd);
     }
 }
@@ -709,7 +688,7 @@ static HRESULT CheckForDuplicateFile(
     __in LONGLONG llFileSize
     )
 {
-    DWORD i;
+    DWORD i = 0;
     HRESULT hr = S_OK;
     UINT er = ERROR_SUCCESS;
 
@@ -916,17 +895,17 @@ static HRESULT UpdateDuplicateFiles(
     LPVOID pv = NULL;
     MS_CABINET_HEADER *pCabinetHeader = NULL;
 
-    hCabinet = ::CreateFileW(pcd->wzCabinetPath, GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_DELETE, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
+    hCabinet = ::CreateFileW(pcd->sczCabinetPath, GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_DELETE, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
     if (INVALID_HANDLE_VALUE == hCabinet)
     {
-        CabcExitWithLastError(hr, "Failed to open cabinet: %ls", pcd->wzCabinetPath);
+        CabcExitWithLastError(hr, "Failed to open cabinet: %ls", pcd->sczCabinetPath);
     }
 
     // Shouldn't need more than 16 MB to get the whole cabinet header into memory so use that as
     // the upper bound for the memory map.
     if (!::GetFileSizeEx(hCabinet, &liCabinetSize))
     {
-        CabcExitWithLastError(hr, "Failed to get size of cabinet: %ls", pcd->wzCabinetPath);
+        CabcExitWithLastError(hr, "Failed to get size of cabinet: %ls", pcd->sczCabinetPath);
     }
 
     if (0 == liCabinetSize.HighPart && liCabinetSize.LowPart < MAX_CABINET_HEADER_SIZE)
@@ -942,11 +921,11 @@ static HRESULT UpdateDuplicateFiles(
     hCabinetMapping = ::CreateFileMappingW(hCabinet, NULL, PAGE_READWRITE | SEC_COMMIT, 0, cbCabinet, NULL);
     if (NULL == hCabinetMapping || INVALID_HANDLE_VALUE == hCabinetMapping)
     {
-        CabcExitWithLastError(hr, "Failed to memory map cabinet file: %ls", pcd->wzCabinetPath);
+        CabcExitWithLastError(hr, "Failed to memory map cabinet file: %ls", pcd->sczCabinetPath);
     }
 
     pv = ::MapViewOfFile(hCabinetMapping, FILE_MAP_WRITE, 0, 0, 0);
-    CabcExitOnNullWithLastError(pv, hr, "Failed to map view of cabinet file: %ls", pcd->wzCabinetPath);
+    CabcExitOnNullWithLastError(pv, hr, "Failed to map view of cabinet file: %ls", pcd->sczCabinetPath);
 
     pCabinetHeader = static_cast<MS_CABINET_HEADER*>(pv);
 
@@ -1155,7 +1134,7 @@ static __callback INT_PTR DIAMONDAPI CabCOpen(
 
     if (INVALID_HANDLE_VALUE == reinterpret_cast<HANDLE>(pFile))
     {
-        CabcExitOnLastError(hr, "failed to open file: %s", pszFile);
+        CabcExitOnLastError(hr, "failed to open file: %hs", pszFile);
     }
 
 LExit:
@@ -1326,11 +1305,12 @@ static __callback BOOL DIAMONDAPI CabCGetTempFile(
 
     HRESULT hr = S_OK;
     char szTempPath[MAX_PATH] = { };
-    DWORD cchTempPath = MAX_PATH;
     DWORD dwProcessId = ::GetCurrentProcessId();
     HANDLE hTempFile = INVALID_HANDLE_VALUE;
 
-    if (MAX_PATH < ::GetTempPathA(cchTempPath, szTempPath))
+    // TODO: Allow user to pass in different temp path in case the default is too long,
+    // and/or see if magic similar to CABC_MAGIC_UNICODE_STRING_MARKER can be used to pass ourselves a path longer than MAX_PATH.
+    if (MAX_PATH < ::GetTempPathA(countof(szTempPath), szTempPath))
     {
         CabcExitWithLastError(hr, "Failed to get temp path during cabinet creation.");
     }
@@ -1339,7 +1319,7 @@ static __callback BOOL DIAMONDAPI CabCGetTempFile(
     {
         LONG dwTempIndex = ::InterlockedIncrement(reinterpret_cast<volatile LONG*>(&dwIndex));
 
-        hr = ::StringCbPrintfA(szFile, cbFile, "%s\\%08x.%03x", szTempPath, dwTempIndex, dwProcessId);
+        hr = ::StringCbPrintfA(szFile, cbFile, "%hs\\%08x.%03x", szTempPath, dwTempIndex, dwProcessId);
         CabcExitOnFailure(hr, "failed to format log file path.");
 
         hTempFile = ::CreateFileA(szFile, 0, FILE_SHARE_DELETE, NULL, CREATE_NEW, FILE_ATTRIBUTE_TEMPORARY | FILE_FLAG_DELETE_ON_CLOSE, NULL);
@@ -1351,7 +1331,11 @@ static __callback BOOL DIAMONDAPI CabCGetTempFile(
         }
         else
         {
-            hr = E_FAIL; // this file was taken so be pessimistic and assume we're not going to find one.
+            hr = HRESULT_FROM_WIN32(::GetLastError()); // this file was taken so be pessimistic and assume we're not going to find one.
+            if (SUCCEEDED(hr))
+            {
+                hr = E_FAIL;
+            }
         }
     }
     CabcExitOnFailure(hr, "failed to find temporary file.");
@@ -1386,7 +1370,7 @@ static __callback BOOL DIAMONDAPI CabCGetNextCabinet(
     if (pccab->iCab == 1)
     {
         pcd->wzFirstCabinetName[0] = '\0';
-        LPCWSTR pwzCabinetName = PathFile(pcd->wzCabinetPath);
+        LPCWSTR pwzCabinetName = PathFile(pcd->sczCabinetPath);
         size_t len = wcsnlen(pwzCabinetName, sizeof(pwzCabinetName));
         if (len > 4)
         {
diff --git a/src/libs/dutil/WixToolset.DUtil/cabutil.cpp b/src/libs/dutil/WixToolset.DUtil/cabutil.cpp
index f3629d57..57463e1a 100644
--- a/src/libs/dutil/WixToolset.DUtil/cabutil.cpp
+++ b/src/libs/dutil/WixToolset.DUtil/cabutil.cpp
@@ -261,15 +261,15 @@ static HRESULT DAPI CabOperation(
     )
 {
     HRESULT hr = S_OK;
-    BOOL fResult;
+    BOOL fResult = FALSE;
 
     LPWSTR sczCabinet = NULL;
     LPWSTR pwz = NULL;
-    CHAR szCabDirectory[MAX_PATH * 4]; // Make sure these are big enough for UTF-8 strings
-    CHAR szCabFile[MAX_PATH * 4];
+    LPSTR pszCabDirectory = NULL;
+    CHAR szCabFile[MAX_PATH * 4] = { }; // Make sure this is big enough for UTF-8 strings
 
-    CAB_CALLBACK_STRUCT ccs;
-    PFNFDINOTIFY pfnFdiNotify;
+    CAB_CALLBACK_STRUCT ccs = { };
+    PFNFDINOTIFY pfnFdiNotify = NULL;
 
     //
     // ensure the cabinet.dll is loaded
@@ -299,15 +299,13 @@ static HRESULT DAPI CabOperation(
     // If a full path was not provided, use the relative current directory.
     if (wzCabinet == pwz)
     {
-        hr = ::StringCchCopyA(szCabDirectory, countof(szCabDirectory), ".\\");
+        hr = StrAnsiAllocStringAnsi(&pszCabDirectory, ".\\", 0);
         CabExitOnFailure(hr, "Failed to copy relative current directory as cabinet directory.");
     }
     else
     {
-        if (!::WideCharToMultiByte(CP_UTF8, 0, sczCabinet, -1, szCabDirectory, countof(szCabDirectory), NULL, NULL))
-        {
-            CabExitWithLastError(hr, "failed to convert cabinet directory to ASCII: %ls", sczCabinet);
-        }
+        hr = StrAnsiAllocString(&pszCabDirectory, sczCabinet, 0, CP_UTF8);
+        CabExitOnFailure(hr, "failed to convert cabinet directory to ASCII: %ls", sczCabinet);
     }
 
     //
@@ -331,7 +329,7 @@ static HRESULT DAPI CabOperation(
         v_pfnNetFx11Notify = pfnNotify;
         pfnFdiNotify = FDINotify;
     }
-    fResult = vpfnFDICopy(vhfdi, szCabFile, szCabDirectory, 0, pfnFdiNotify, NULL, static_cast<void*>(&ccs));
+    fResult = vpfnFDICopy(vhfdi, szCabFile, pszCabDirectory, 0, pfnFdiNotify, NULL, static_cast<void*>(&ccs));
     if (!fResult && !ccs.fStopExtracting)   // if something went wrong and it wasn't us just stopping the extraction, then return a failure
     {
         CabExitWithLastError(hr, "failed to extract cabinet file: %ls", sczCabinet);
@@ -339,6 +337,7 @@ static HRESULT DAPI CabOperation(
 
 LExit:
     ReleaseStr(sczCabinet);
+    ReleaseStr(pszCabDirectory);
     v_pfnNetFx11Notify = NULL;
 
     return hr;
@@ -493,14 +492,15 @@ static __callback INT_PTR DIAMONDAPI CabExtractCallback(__in FDINOTIFICATIONTYPE
     INT_PTR ipResult = 0;   // result to return on success
 
     CAB_CALLBACK_STRUCT* pccs = static_cast<CAB_CALLBACK_STRUCT*>(pFDINotify->pv);
-    LPCSTR sz;
-    WCHAR wz[MAX_PATH];
-    FILETIME ft;
+    LPCSTR sz = NULL;
+    LPWSTR pwz = NULL;
+    LPWSTR pwzPath = NULL;
+    FILETIME ft = { };
 
     switch (iNotification)
     {
     case fdintCOPY_FILE:  // begin extracting a resource from cabinet
-        CabExitOnNull(pFDINotify->psz1, hr, E_INVALIDARG, "No cabinet file ID given to convert");
+        Assert(pccs && pFDINotify->psz1);
         CabExitOnNull(pccs, hr, E_INVALIDARG, "Failed to call cabextract callback, because no callback struct was provided");
 
         if (pccs->fStopExtracting)
@@ -510,40 +510,37 @@ static __callback INT_PTR DIAMONDAPI CabExtractCallback(__in FDINOTIFICATIONTYPE
 
         // convert params to useful variables
         sz = static_cast<LPCSTR>(pFDINotify->psz1);
-        if (!::MultiByteToWideChar(CP_ACP, 0, sz, -1, wz, countof(wz)))
-        {
-            CabExitWithLastError(hr, "failed to convert cabinet file id to unicode: %s", sz);
-        }
+        CabExitOnNull(sz, hr, E_INVALIDARG, "No cabinet file ID given to convert");
+
+        hr = StrAllocStringAnsi(&pwz, sz, 0, CP_ACP);
+        CabExitOnFailure(hr, "failed to convert cabinet file id to unicode: %hs", sz);
 
         if (pccs->pfnProgress)
         {
-            hr = pccs->pfnProgress(TRUE, wz, pccs->pvContext);
+            hr = pccs->pfnProgress(TRUE, pwz, pccs->pvContext);
             if (S_OK != hr)
             {
                 ExitFunction();
             }
         }
 
-        if (L'*' == *pccs->pwzExtract || 0 == lstrcmpW(pccs->pwzExtract, wz))
+        if (L'*' == *pccs->pwzExtract || 0 == lstrcmpW(pccs->pwzExtract, pwz))
         {
             // get the created date for the resource in the cabinet
             FILETIME ftLocal;
             if (!::DosDateTimeToFileTime(pFDINotify->date, pFDINotify->time, &ftLocal))
             {
-                CabExitWithLastError(hr, "failed to get time for resource: %ls", wz);
+                CabExitWithLastError(hr, "failed to get time for resource: %ls", pwz);
             }
             ::LocalFileTimeToFileTime(&ftLocal, &ft);
 
-            WCHAR wzPath[MAX_PATH];
-            hr = ::StringCchCopyW(wzPath, countof(wzPath), pccs->pwzExtractDir);
-            CabExitOnFailure(hr, "failed to copy in extract directory: %ls for file: %ls", pccs->pwzExtractDir, wz);
-            hr = ::StringCchCatW(wzPath, countof(wzPath), wz);
-            CabExitOnFailure(hr, "failed to concat onto path: %ls file: %ls", wzPath, wz);
+            hr = PathConcat(pccs->pwzExtractDir, pwz, &pwzPath);
+            CabExitOnFailure(hr, "failed to concat onto path: %ls file: %ls", pccs->pwzExtractDir, pwz);
 
-            hFile = OpenFileWithRetry(wzPath, GENERIC_WRITE, CREATE_ALWAYS);
+            hFile = OpenFileWithRetry(pwzPath, GENERIC_WRITE, CREATE_ALWAYS);
             if (INVALID_HANDLE_VALUE == hFile)
             {
-                CabExitWithLastError(hr, "failed to create file: %ls", wzPath);
+                CabExitWithLastError(hr, "failed to create file: %ls", pwzPath);
             }
 
             ::SetFileTime(hFile, &ft, &ft, &ft);   // try to set the file time (who cares if it fails)
@@ -567,17 +564,15 @@ static __callback INT_PTR DIAMONDAPI CabExtractCallback(__in FDINOTIFICATIONTYPE
 
         break;
     case fdintCLOSE_FILE_INFO:  // resource extraction complete
-        Assert(pFDINotify->hf && pFDINotify->psz1);
+        Assert(pFDINotify->hf && pccs && pFDINotify->psz1);
         CabExitOnNull(pccs, hr, E_INVALIDARG, "Failed to call cabextract callback, because no callback struct was provided");
 
         // convert params to useful variables
         sz = static_cast<LPCSTR>(pFDINotify->psz1);
         CabExitOnNull(sz, hr, E_INVALIDARG, "Failed to convert cabinet file id, because no cabinet file id was provided");
 
-        if (!::MultiByteToWideChar(CP_ACP, 0, sz, -1, wz, countof(wz)))
-        {
-            CabExitWithLastError(hr, "failed to convert cabinet file id to unicode: %s", sz);
-        }
+        hr = StrAllocStringAnsi(&pwz, sz, 0, CP_ACP);
+        CabExitOnFailure(hr, "failed to convert cabinet file id to unicode: %hs", sz);
 
         if (NULL != pFDINotify->hf)  // just close the file
         {
@@ -586,7 +581,7 @@ static __callback INT_PTR DIAMONDAPI CabExtractCallback(__in FDINOTIFICATIONTYPE
 
         if (pccs->pfnProgress)
         {
-            hr = pccs->pfnProgress(FALSE, wz, pccs->pvContext);
+            hr = pccs->pfnProgress(FALSE, pwz, pccs->pvContext);
         }
 
         if (S_OK == hr && L'*' == *pccs->pwzExtract)   // if everything is okay and we're extracting all files, keep going
@@ -613,5 +608,8 @@ static __callback INT_PTR DIAMONDAPI CabExtractCallback(__in FDINOTIFICATIONTYPE
 LExit:
     ReleaseFileHandle(hFile);
 
+    ReleaseStr(pwz);
+    ReleaseStr(pwzPath);
+
     return (S_OK == hr) ? ipResult : -1;
 }
diff --git a/src/libs/dutil/WixToolset.DUtil/dirutil.cpp b/src/libs/dutil/WixToolset.DUtil/dirutil.cpp
index 94eab9e7..2c02225d 100644
--- a/src/libs/dutil/WixToolset.DUtil/dirutil.cpp
+++ b/src/libs/dutil/WixToolset.DUtil/dirutil.cpp
@@ -59,34 +59,10 @@ LExit:
  *******************************************************************/
 extern "C" HRESULT DAPI DirCreateTempPath(
     __in_z LPCWSTR wzPrefix,
-    __out_ecount_z(cchPath) LPWSTR wzPath,
-    __in DWORD cchPath
+    __out_opt LPWSTR* psczTempFile
     )
 {
-    Assert(wzPrefix);
-    Assert(wzPath);
-
-    HRESULT hr = S_OK;
-
-    WCHAR wzDir[MAX_PATH];
-    WCHAR wzFile[MAX_PATH];
-    DWORD cch = 0;
-
-    cch = ::GetTempPathW(countof(wzDir), wzDir);
-    if (!cch || cch >= countof(wzDir))
-    {
-        DirExitWithLastError(hr, "Failed to GetTempPath.");
-    }
-
-    if (!::GetTempFileNameW(wzDir, wzPrefix, 0, wzFile))
-    {
-        DirExitWithLastError(hr, "Failed to GetTempFileName.");
-    }
-
-    hr = ::StringCchCopyW(wzPath, cchPath, wzFile);
-
-LExit:
-    return hr;
+    return PathCreateTempFile(NULL, NULL, 0, wzPrefix, 0, psczTempFile, NULL);
 }
 
 
@@ -192,18 +168,19 @@ extern "C" HRESULT DAPI DirEnsureDeleteEx(
     Assert(wzPath && *wzPath);
 
     HRESULT hr = S_OK;
-    DWORD er;
+    DWORD er = ERROR_SUCCESS;
 
-    DWORD dwAttrib;
+    DWORD dwAttrib = 0;
     HANDLE hFind = INVALID_HANDLE_VALUE;
     LPWSTR sczDelete = NULL;
-    WIN32_FIND_DATAW wfd;
+    WIN32_FIND_DATAW wfd = { };
 
     BOOL fDeleteFiles = (DIR_DELETE_FILES == (dwFlags & DIR_DELETE_FILES));
     BOOL fRecurse = (DIR_DELETE_RECURSE == (dwFlags & DIR_DELETE_RECURSE));
     BOOL fScheduleDelete = (DIR_DELETE_SCHEDULE == (dwFlags & DIR_DELETE_SCHEDULE));
-    WCHAR wzTempDirectory[MAX_PATH] = { };
-    WCHAR wzTempPath[MAX_PATH] = { };
+    WCHAR wzSafeFileName[MAX_PATH + 1] = { };
+    LPWSTR sczTempDirectory = NULL;
+    LPWSTR sczTempPath = NULL;
 
     if (-1 == (dwAttrib = ::GetFileAttributesW(wzPath)))
     {
@@ -231,10 +208,8 @@ extern "C" HRESULT DAPI DirEnsureDeleteEx(
         {
             if (fScheduleDelete)
             {
-                if (!::GetTempPathW(countof(wzTempDirectory), wzTempDirectory))
-                {
-                    DirExitWithLastError(hr, "Failed to get temp directory.");
-                }
+                hr = PathGetTempPath(&sczTempDirectory, NULL);
+                DirExitOnFailure(hr, "Failed to get temp directory.");
             }
 
             // Delete everything in this directory.
@@ -256,10 +231,11 @@ extern "C" HRESULT DAPI DirEnsureDeleteEx(
                 }
 
                 // For extra safety and to silence OACR.
-                wfd.cFileName[MAX_PATH - 1] = L'\0';
+                hr = ::StringCchCopyNExW(wzSafeFileName, countof(wzSafeFileName), wfd.cFileName, countof(wfd.cFileName), NULL, NULL, STRSAFE_FILL_BEHIND_NULL | STRSAFE_NULL_ON_FAILURE);
+                DirExitOnFailure(hr, "Failed to ensure file name was null terminated.");
 
-                hr = PathConcat(wzPath, wfd.cFileName, &sczDelete);
-                DirExitOnFailure(hr, "Failed to concat filename '%ls' to directory: %ls", wfd.cFileName, wzPath);
+                hr = PathConcat(wzPath, wzSafeFileName, &sczDelete);
+                DirExitOnFailure(hr, "Failed to concat filename '%ls' to directory: %ls", wzSafeFileName, wzPath);
 
                 if (fRecurse && wfd.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
                 {
@@ -288,16 +264,14 @@ extern "C" HRESULT DAPI DirEnsureDeleteEx(
                     {
                         if (fScheduleDelete)
                         {
-                            if (!::GetTempFileNameW(wzTempDirectory, L"DEL", 0, wzTempPath))
-                            {
-                                DirExitWithLastError(hr, "Failed to get temp file to move to.");
-                            }
+                            hr = PathGetTempFileName(sczTempDirectory, L"DEL", 0, &sczTempPath);
+                            DirExitOnFailure(hr, "Failed to get temp file to move to.");
 
                             // Try to move the file to the temp directory then schedule for delete,
                             // otherwise just schedule for delete.
-                            if (::MoveFileExW(sczDelete, wzTempPath, MOVEFILE_REPLACE_EXISTING))
+                            if (::MoveFileExW(sczDelete, sczTempPath, MOVEFILE_REPLACE_EXISTING))
                             {
-                                ::MoveFileExW(wzTempPath, NULL, MOVEFILE_DELAY_UNTIL_REBOOT);
+                                ::MoveFileExW(sczTempPath, NULL, MOVEFILE_DELAY_UNTIL_REBOOT);
                             }
                             else
                             {
@@ -348,6 +322,8 @@ extern "C" HRESULT DAPI DirEnsureDeleteEx(
 LExit:
     ReleaseFileFindHandle(hFind);
     ReleaseStr(sczDelete);
+    ReleaseStr(sczTempDirectory);
+    ReleaseStr(sczTempPath);
 
     return hr;
 }
diff --git a/src/libs/dutil/WixToolset.DUtil/fileutil.cpp b/src/libs/dutil/WixToolset.DUtil/fileutil.cpp
index 9f68ee52..ac407916 100644
--- a/src/libs/dutil/WixToolset.DUtil/fileutil.cpp
+++ b/src/libs/dutil/WixToolset.DUtil/fileutil.cpp
@@ -1284,21 +1284,18 @@ extern "C" HRESULT DAPI FileCreateTempW(
     Assert(wzPrefix && *wzPrefix);
     HRESULT hr = E_FAIL;
 
-    WCHAR wzTempPath[MAX_PATH];
-    DWORD cchTempPath = countof(wzTempPath);
+    LPWSTR pwzTempPath = NULL;
     LPWSTR pwzTempFile = NULL;
 
     HANDLE hTempFile = INVALID_HANDLE_VALUE;
     int i = 0;
 
-    if (!::GetTempPathW(cchTempPath, wzTempPath))
-    {
-        FileExitOnLastError(hr, "failed to get temp path");
-    }
+    hr = PathGetTempPath(&pwzTempPath, NULL);
+    FileExitOnFailure(hr, "failed to get temp path");
 
     for (i = 0; i < 1000 && INVALID_HANDLE_VALUE == hTempFile; ++i)
     {
-        hr = StrAllocFormatted(&pwzTempFile, L"%s%s%05d.%s", wzTempPath, wzPrefix, i, wzExtension);
+        hr = StrAllocFormatted(&pwzTempFile, L"%s%s%05d.%s", pwzTempPath, wzPrefix, i, wzExtension);
         FileExitOnFailure(hr, "failed to allocate memory for temp filename");
 
         hTempFile = ::CreateFileW(pwzTempFile, GENERIC_WRITE, FILE_SHARE_READ, NULL, CREATE_NEW, FILE_ATTRIBUTE_NORMAL, NULL);
@@ -1330,6 +1327,7 @@ extern "C" HRESULT DAPI FileCreateTempW(
 LExit:
     ReleaseFile(hTempFile);
     ReleaseStr(pwzTempFile);
+    ReleaseStr(pwzTempPath);
 
     return hr;
 }
diff --git a/src/libs/dutil/WixToolset.DUtil/inc/dirutil.h b/src/libs/dutil/WixToolset.DUtil/inc/dirutil.h
index 42268a16..b8fc0431 100644
--- a/src/libs/dutil/WixToolset.DUtil/inc/dirutil.h
+++ b/src/libs/dutil/WixToolset.DUtil/inc/dirutil.h
@@ -20,8 +20,7 @@ BOOL DAPI DirExists(
 
 HRESULT DAPI DirCreateTempPath(
     __in_z LPCWSTR wzPrefix,
-    __out_ecount_z(cchPath) LPWSTR wzPath,
-    __in DWORD cchPath
+    __out_opt LPWSTR* psczTempFile
     );
 
 HRESULT DAPI DirEnsureExists(
diff --git a/src/libs/dutil/WixToolset.DUtil/inc/pathutil.h b/src/libs/dutil/WixToolset.DUtil/inc/pathutil.h
index 971ef887..de46b95d 100644
--- a/src/libs/dutil/WixToolset.DUtil/inc/pathutil.h
+++ b/src/libs/dutil/WixToolset.DUtil/inc/pathutil.h
@@ -159,19 +159,31 @@ DAPI_(HRESULT) PathRelativeToModule(
 /*******************************************************************
  PathCreateTempFile
 
- Note: if wzDirectory is null, ::GetTempPath() will be used instead.
+ Note: if wzDirectory is null, ::GetTempPath2() will be used instead.
        if wzFileNameTemplate is null, GetTempFileName() will be used instead.
 *******************************************************************/
 DAPI_(HRESULT) PathCreateTempFile(
     __in_opt LPCWSTR wzDirectory,
     __in_opt __format_string LPCWSTR wzFileNameTemplate,
     __in DWORD dwUniqueCount,
+    __in_z LPCWSTR wzPrefix,
     __in DWORD dwFileAttributes,
     __out_opt LPWSTR* psczTempFile,
     __out_opt HANDLE* phTempFile
     );
 
 /*******************************************************************
+ PathGetTempFileName - wrapper around ::GetTempFileName.
+    If the wzPathName is too long, it will use its own algorithm.
+*******************************************************************/
+DAPI_(HRESULT) PathGetTempFileName(
+    __in LPCWSTR wzPathName,
+    __in LPCWSTR wzPrefixString,
+    __in UINT uUnique,
+    __out LPWSTR* psczTempFileName
+    );
+
+/*******************************************************************
  PathCreateTimeBasedTempFile - creates an empty temp file based on current
                            system time
 ********************************************************************/
@@ -187,7 +199,7 @@ DAPI_(HRESULT) PathCreateTimeBasedTempFile(
 /*******************************************************************
  PathCreateTempDirectory
 
- Note: if wzDirectory is null, ::GetTempPath() will be used instead.
+ Note: if wzDirectory is null, ::GetTempPath2() will be used instead.
 *******************************************************************/
 DAPI_(HRESULT) PathCreateTempDirectory(
     __in_opt LPCWSTR wzDirectory,
@@ -201,7 +213,24 @@ DAPI_(HRESULT) PathCreateTempDirectory(
     that is backslash terminated.
 *******************************************************************/
 DAPI_(HRESULT) PathGetTempPath(
-    __out_z LPWSTR* psczTempPath
+    __out_z LPWSTR* psczTempPath,
+    __out_opt SIZE_T* pcch
+    );
+
+/*******************************************************************
+ PathGetSystemDirectory - returns the path to the system folder
+    that is backslash terminated.
+*******************************************************************/
+DAPI_(HRESULT) PathGetSystemDirectory(
+    __out_z LPWSTR* psczSystemPath
+    );
+
+/*******************************************************************
+ PathGetSystemWow64Directory - returns the path to the system WoW 64 folder
+    that is backslash terminated.
+*******************************************************************/
+DAPI_(HRESULT) PathGetSystemWow64Directory(
+    __out_z LPWSTR* psczSystemPath
     );
 
 /*******************************************************************
@@ -223,12 +252,11 @@ DAPI_(HRESULT) PathGetSystemTempPaths(
     );
 
 /*******************************************************************
- PathGetKnownFolder - returns the path to a well-known shell folder
-
+ PathGetVolumePathName - wrapper for ::GetVolumePathNameW.
 *******************************************************************/
-DAPI_(HRESULT) PathGetKnownFolder(
-    __in int csidl,
-    __out LPWSTR* psczKnownFolder
+DAPI_(HRESULT) PathGetVolumePathName(
+    __in_z LPCWSTR wzFileName,
+    __out_z LPWSTR* psczVolumePathName
     );
 
 /*******************************************************************
@@ -340,6 +368,20 @@ DAPI_(HRESULT) PathGetHierarchyArray(
     __inout LPUINT pcPathArray
     );
 
+/********************************************************************
+ Path2FunctionAllowFallback - allow functions only available in newer versions of Windows.
+                              Typically used for unit testing.
+
+*********************************************************************/
+void DAPI Path2FunctionAllowFallback();
+
+/********************************************************************
+ Path2FunctionForceFallback - ignore functions only available in newer versions of Windows.
+                              Typically used for unit testing.
+
+*********************************************************************/
+void DAPI Path2FunctionForceFallback();
+
 /*******************************************************************
  PathCanonicalizePath - wrapper around PathCanonicalizeW.
 *******************************************************************/
@@ -349,6 +391,15 @@ DAPI_(HRESULT) PathCanonicalizePath(
     );
 
 /*******************************************************************
+ PathAllocCanonicalizePath - wrapper around PathAllocCanonicalize.
+*******************************************************************/
+DAPI_(HRESULT) PathAllocCanonicalizePath(
+    __in_z LPCWSTR wzPath,
+    __in DWORD dwFlags,
+    __deref_out_z LPWSTR* psczCanonicalized
+    );
+
+/*******************************************************************
  PathCanonicalizeForComparison - canonicalizes the path based on the given flags.
     . and .. directories are collapsed.
     All / are replaced with \.
diff --git a/src/libs/dutil/WixToolset.DUtil/inc/shelutil.h b/src/libs/dutil/WixToolset.DUtil/inc/shelutil.h
index 0b9f539d..2ee7ce87 100644
--- a/src/libs/dutil/WixToolset.DUtil/inc/shelutil.h
+++ b/src/libs/dutil/WixToolset.DUtil/inc/shelutil.h
@@ -33,10 +33,25 @@ HRESULT DAPI ShelExecUnelevated(
     __in_z_opt LPCWSTR wzWorkingDirectory,
     __in int nShowCmd
     );
+
+/********************************************************************
+ ShelGetFolder() - translates the CSIDL into KNOWNFOLDERID and calls ShelGetKnownFolder.
+    If that returns E_NOTIMPL then falls back to ::SHGetFolderPathW.
+    The CSIDL_FLAG values are not supported, CSIDL_FLAG_CREATE is always used.
+    The path is backslash terminated.
+
+*******************************************************************/
 HRESULT DAPI ShelGetFolder(
     __out_z LPWSTR* psczFolderPath,
     __in int csidlFolder
     );
+
+/********************************************************************
+ ShelGetKnownFolder() - gets a folder by KNOWNFOLDERID with ::SHGetKnownFolderPath.
+    The path is backslash terminated.
+
+ Note: return E_NOTIMPL if called on pre-Vista operating systems.
+*******************************************************************/
 HRESULT DAPI ShelGetKnownFolder(
     __out_z LPWSTR* psczFolderPath,
     __in REFKNOWNFOLDERID rfidFolder
diff --git a/src/libs/dutil/WixToolset.DUtil/logutil.cpp b/src/libs/dutil/WixToolset.DUtil/logutil.cpp
index 88a90d8c..3a130b4e 100644
--- a/src/libs/dutil/WixToolset.DUtil/logutil.cpp
+++ b/src/libs/dutil/WixToolset.DUtil/logutil.cpp
@@ -684,9 +684,10 @@ LExit:
 extern "C" HRESULT DAPI LogHeader()
 {
     HRESULT hr = S_OK;
-    WCHAR wzComputerName[MAX_PATH];
+    WCHAR wzComputerName[MAX_COMPUTERNAME_LENGTH + 1] = { };
     DWORD cchComputerName = countof(wzComputerName);
-    WCHAR wzPath[MAX_PATH];
+    LPWSTR sczPath = NULL;
+    LPCWSTR wzPath = NULL;
     DWORD dwMajorVersion = 0;
     DWORD dwMinorVersion = 0;
     LPCSTR szLevel = LOGUTIL_UNKNOWN;
@@ -695,12 +696,19 @@ extern "C" HRESULT DAPI LogHeader()
     //
     // get the interesting data
     //
-    if (!::GetModuleFileNameW(NULL, wzPath, countof(wzPath)))
+
+    hr = PathForCurrentProcess(&sczPath, NULL);
+    if (FAILED(hr))
+    {
+        wzPath = L"";
+    }
+    else
     {
-        memset(wzPath, 0, sizeof(wzPath));
+        wzPath = sczPath;
+
+        hr = FileVersion(wzPath, &dwMajorVersion, &dwMinorVersion);
     }
 
-    hr = FileVersion(wzPath, &dwMajorVersion, &dwMinorVersion);
     if (FAILED(hr))
     {
         dwMajorVersion = 0;
@@ -743,6 +751,7 @@ extern "C" HRESULT DAPI LogHeader()
     hr = S_OK;
 
     ReleaseStr(sczCurrentDateTime);
+    ReleaseStr(sczPath);
 
     return hr;
 }
diff --git a/src/libs/dutil/WixToolset.DUtil/path2utl.cpp b/src/libs/dutil/WixToolset.DUtil/path2utl.cpp
index 3c4b2f88..862a743d 100644
--- a/src/libs/dutil/WixToolset.DUtil/path2utl.cpp
+++ b/src/libs/dutil/WixToolset.DUtil/path2utl.cpp
@@ -19,6 +19,65 @@
 #define PathExitOnGdipFailure(g, x, s, ...) ExitOnGdipFailureSource(DUTIL_SOURCE_PATHUTIL, g, x, s, __VA_ARGS__)
 
 
+typedef HRESULT(WINAPI* PFN_PATH_ALLOC_CANONICALIZE)(
+    __in LPCWSTR wzSource,
+    __in DWORD dwFlags,
+    __out_z LPWSTR* psczPathOut
+    );
+
+static BOOL vfInitialized = FALSE;
+static HMODULE vhPathApiSet_1_1_0 = NULL;
+static PFN_PATH_ALLOC_CANONICALIZE vpfnPathAllocCanonicalize = NULL;
+static BOOL vfForceFallback = FALSE;
+
+// from PathCch.h
+#ifndef PATHCCH_ALLOW_LONG_PATHS
+#define PATHCCH_ALLOW_LONG_PATHS       0x01
+#endif
+
+static HRESULT Initialize()
+{
+    HRESULT hr = S_OK;
+    DWORD er = ERROR_SUCCESS;
+
+    if (vfInitialized)
+    {
+        ExitFunction();
+    }
+
+    hr = LoadSystemApiSet(L"api-ms-win-core-path-l1-1-0.dll", &vhPathApiSet_1_1_0);
+    if (E_MODNOTFOUND == hr)
+    {
+        hr = E_NOTIMPL;
+    }
+    PathExitOnFailure(hr, "Failed to load api-ms-win-core-path-l1-1-0.dll");
+
+    vpfnPathAllocCanonicalize = reinterpret_cast<PFN_PATH_ALLOC_CANONICALIZE>(::GetProcAddress(vhPathApiSet_1_1_0, "PathAllocCanonicalize"));
+    if (!vpfnPathAllocCanonicalize)
+    {
+        er = ::GetLastError();
+        PathExitWithRootFailure(hr, ERROR_PROC_NOT_FOUND == er ? E_NOTIMPL : HRESULT_FROM_WIN32(er), "Failed to get address of PathAllocCanonicalize.");
+    }
+
+    vfInitialized = TRUE;
+
+LExit:
+    return hr;
+}
+
+
+DAPI_(void) Path2FunctionAllowFallback()
+{
+    vfForceFallback = FALSE;
+}
+
+
+DAPI_(void) Path2FunctionForceFallback()
+{
+    vfForceFallback = TRUE;
+}
+
+
 DAPI_(HRESULT) PathCanonicalizePath(
     __in_z LPCWSTR wzPath,
     __deref_out_z LPWSTR* psczCanonicalized
@@ -43,6 +102,37 @@ LExit:
     return hr;
 }
 
+DAPI_(HRESULT) PathAllocCanonicalizePath(
+    __in_z LPCWSTR wzPath,
+    __in DWORD dwFlags,
+    __deref_out_z LPWSTR* psczCanonicalized
+    )
+{
+    HRESULT hr = S_OK;
+    LPWSTR sczCanonicalizedPath = NULL;
+
+    hr = Initialize();
+    if (E_NOTIMPL == hr || SUCCEEDED(hr) && !vpfnPathAllocCanonicalize)
+    {
+        ExitFunction1(hr = E_NOTIMPL);
+    }
+    PathExitOnFailure(hr, "Failed to initialize path2utl.");
+
+    hr = vpfnPathAllocCanonicalize(wzPath, dwFlags, &sczCanonicalizedPath);
+    PathExitOnFailure(hr, "Failed to canonicalize: %ls", wzPath);
+
+    hr = StrAllocString(psczCanonicalized, sczCanonicalizedPath, 0);
+    PathExitOnFailure(hr, "Failed to copy the canonicalized path.");
+
+LExit:
+    if (sczCanonicalizedPath)
+    {
+        ::LocalFree(sczCanonicalizedPath);
+    }
+
+    return hr;
+}
+
 DAPI_(HRESULT) PathCanonicalizeForComparison(
     __in_z LPCWSTR wzPath,
     __in DWORD dwCanonicalizeFlags,
@@ -75,7 +165,19 @@ DAPI_(HRESULT) PathCanonicalizeForComparison(
 
     if (*wzNormalizedPath)
     {
-        hr = PathCanonicalizePath(wzNormalizedPath, psczCanonicalized);
+        if (!vfForceFallback)
+        {
+            hr = PathAllocCanonicalizePath(wzNormalizedPath, PATHCCH_ALLOW_LONG_PATHS, psczCanonicalized);
+        }
+        else
+        {
+            hr = E_NOTIMPL;
+        }
+
+        if (E_NOTIMPL == hr)
+        {
+            hr = PathCanonicalizePath(wzNormalizedPath, psczCanonicalized);
+        }
         PathExitOnFailure(hr, "Failed to canonicalize: %ls", wzNormalizedPath);
     }
     else
@@ -273,33 +375,52 @@ DAPI_(HRESULT) PathSystemWindowsSubdirectory(
     )
 {
     HRESULT hr = S_OK;
-    WCHAR wzTempPath[MAX_PATH + 1] = { };
+    LPWSTR sczWindowsPath = NULL;
+    DWORD cchBuffer = MAX_PATH + 1;
     DWORD cch = 0;
 
-    cch = ::GetSystemWindowsDirectoryW(wzTempPath, countof(wzTempPath));
-    if (!cch)
-    {
-        PathExitWithLastError(hr, "Failed to get Windows directory path.");
-    }
-    else if (cch >= countof(wzTempPath))
+    hr = StrAlloc(&sczWindowsPath, cchBuffer);
+    PathExitOnFailure(hr, "Failed to alloc Windows directory path.");
+
+    cch = ::GetSystemWindowsDirectoryW(sczWindowsPath, cchBuffer);
+    PathExitOnNullWithLastError(cch, hr, "Failed to get Windows directory path with default size.");
+
+    cch += 1; // add 1 for null terminator.
+
+    if (cch > cchBuffer)
     {
-        PathExitWithRootFailure(hr, E_INSUFFICIENT_BUFFER, "Windows directory path too long.");
+        hr = StrAlloc(&sczWindowsPath, cch);
+        PathExitOnFailure(hr, "Failed to realloc Windows directory path.");
+
+        cchBuffer = cch;
+
+        cch = ::GetSystemWindowsDirectoryW(sczWindowsPath, cchBuffer);
+        PathExitOnNullWithLastError(cch, hr, "Failed to get Windows directory path with returned size.");
+
+        cch += 1; // add 1 for null terminator.
+
+        if (cch > cchBuffer)
+        {
+            PathExitWithRootFailure(hr, E_INSUFFICIENT_BUFFER, "Failed to get Windows directory path with returned size.");
+        }
     }
 
     if (wzSubdirectory)
     {
-        hr = PathConcatRelativeToBase(wzTempPath, wzSubdirectory, psczFullPath);
+        hr = PathConcatRelativeToBase(sczWindowsPath, wzSubdirectory, psczFullPath);
         PathExitOnFailure(hr, "Failed to concat subdirectory on Windows directory path.");
     }
     else
     {
-        hr = StrAllocString(psczFullPath, wzTempPath, 0);
-        PathExitOnFailure(hr, "Failed to copy Windows directory path.");
+        *psczFullPath = sczWindowsPath;
+        sczWindowsPath = NULL;
     }
 
     hr = PathBackslashTerminate(psczFullPath);
     PathExitOnFailure(hr, "Failed to terminate Windows directory path with backslash.");
 
 LExit:
+    ReleaseStr(sczWindowsPath);
+
     return hr;
 }
diff --git a/src/libs/dutil/WixToolset.DUtil/pathutil.cpp b/src/libs/dutil/WixToolset.DUtil/pathutil.cpp
index 0e2a5dec..dd5385fc 100644
--- a/src/libs/dutil/WixToolset.DUtil/pathutil.cpp
+++ b/src/libs/dutil/WixToolset.DUtil/pathutil.cpp
@@ -20,6 +20,11 @@
 
 #define PATH_GOOD_ENOUGH 64
 
+typedef DWORD(APIENTRY* PFN_GETTEMPPATH2W)(
+    __in DWORD BufferLength,
+    __out LPWSTR Buffer
+    );
+
 static BOOL IsPathSeparatorChar(
     __in WCHAR wc
     );
@@ -527,28 +532,55 @@ DAPI_(HRESULT) PathForCurrentProcess(
     )
 {
     HRESULT hr = S_OK;
-    DWORD cch = MAX_PATH;
+    WCHAR smallBuffer[1] = { };
+    SIZE_T cchMax = 0;
+    DWORD cchBuffer = 0;
+    DWORD cch = 0;
+    DWORD dwMaxAttempts = 20;
 
-    do
+    // GetModuleFileNameW didn't originally set the last error when the buffer was too small.
+    ::SetLastError(ERROR_SUCCESS);
+
+    cch = ::GetModuleFileNameW(hModule, smallBuffer, countof(smallBuffer));
+    PathExitOnNullWithLastError(cch, hr, "Failed to get size of path for executing process.");
+
+    if (*psczFullPath && ERROR_INSUFFICIENT_BUFFER == ::GetLastError())
     {
-        hr = StrAlloc(psczFullPath, cch);
-        PathExitOnFailure(hr, "Failed to allocate string for module path.");
+        hr = StrMaxLength(*psczFullPath, &cchMax);
+        PathExitOnFailure(hr, "Failed to get max length of input buffer.");
+
+        cchBuffer = (DWORD)min(DWORD_MAX, cchMax);
+    }
+    else
+    {
+        cchBuffer = MAX_PATH + 1;
+
+        hr = StrAlloc(psczFullPath, cchBuffer);
+        PathExitOnFailure(hr, "Failed to allocate space for module path.");
+    }
+
+    ::SetLastError(ERROR_SUCCESS);
 
-        DWORD cchRequired = ::GetModuleFileNameW(hModule, *psczFullPath, cch);
-        if (0 == cchRequired)
+    for (DWORD i = 0; i < dwMaxAttempts; ++i)
+    {
+        cch = ::GetModuleFileNameW(hModule, *psczFullPath, cchBuffer);
+        PathExitOnNullWithLastError(cch, hr, "Failed to get path for executing process.");
+
+        if (ERROR_INSUFFICIENT_BUFFER != ::GetLastError())
         {
-            PathExitWithLastError(hr, "Failed to get path for executing process.");
+            break;
         }
-        else if (cchRequired == cch)
+
+        if ((dwMaxAttempts - 1) == i)
         {
-            cch = cchRequired + 1;
-            hr = HRESULT_FROM_WIN32(ERROR_INSUFFICIENT_BUFFER);
+            PathExitWithRootFailure(hr, E_FAIL, "Unexpected failure getting path for executing process.");
         }
-        else
-        {
-            hr = S_OK;
-        }
-    } while (HRESULT_FROM_WIN32(ERROR_INSUFFICIENT_BUFFER) == hr);
+
+        cchBuffer *= 2;
+
+        hr = StrAlloc(psczFullPath, cchBuffer);
+        PathExitOnFailure(hr, "Failed to re-allocate more space for module path.");
+    }
 
 LExit:
     return hr;
@@ -582,17 +614,18 @@ DAPI_(HRESULT) PathCreateTempFile(
     __in_opt LPCWSTR wzDirectory,
     __in_opt __format_string LPCWSTR wzFileNameTemplate,
     __in DWORD dwUniqueCount,
+    __in_z LPCWSTR wzPrefix,
     __in DWORD dwFileAttributes,
     __out_opt LPWSTR* psczTempFile,
     __out_opt HANDLE* phTempFile
     )
 {
-    AssertSz(0 < dwUniqueCount, "Must specify a non-zero unique count.");
+    Assert(wzPrefix);
+    AssertSz(!wzFileNameTemplate || !*wzFileNameTemplate || 0 < dwUniqueCount, "Must specify a non-zero unique count.");
 
     HRESULT hr = S_OK;
 
     LPWSTR sczTempPath = NULL;
-    DWORD cchTempPath = MAX_PATH;
 
     HANDLE hTempFile = INVALID_HANDLE_VALUE;
     LPWSTR scz = NULL;
@@ -605,13 +638,8 @@ DAPI_(HRESULT) PathCreateTempFile(
     }
     else
     {
-        hr = StrAlloc(&sczTempPath, cchTempPath);
-        PathExitOnFailure(hr, "Failed to allocate memory for the temp path.");
-
-        if (!::GetTempPathW(cchTempPath, sczTempPath))
-        {
-            PathExitWithLastError(hr, "Failed to get temp path.");
-        }
+        hr = PathGetTempPath(&sczTempPath, NULL);
+        PathExitOnFailure(hr, "Failed to get temp path.");
     }
 
     if (wzFileNameTemplate && *wzFileNameTemplate)
@@ -621,7 +649,7 @@ DAPI_(HRESULT) PathCreateTempFile(
             hr = StrAllocFormatted(&scz, wzFileNameTemplate, i);
             PathExitOnFailure(hr, "Failed to allocate memory for file template.");
 
-            hr = StrAllocFormatted(&sczTempFile, L"%s%s", sczTempPath, scz);
+            hr = StrAllocFormatted(&sczTempFile, L"%ls%ls", sczTempPath, scz);
             PathExitOnFailure(hr, "Failed to allocate temp file name.");
 
             hTempFile = ::CreateFileW(sczTempFile, GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_DELETE, NULL, CREATE_NEW, dwFileAttributes, NULL);
@@ -642,13 +670,8 @@ DAPI_(HRESULT) PathCreateTempFile(
     // the system to provide us a temp file using its built-in mechanism.
     if (INVALID_HANDLE_VALUE == hTempFile)
     {
-        hr = StrAlloc(&sczTempFile, MAX_PATH);
-        PathExitOnFailure(hr, "Failed to allocate memory for the temp path");
-
-        if (!::GetTempFileNameW(sczTempPath, L"TMP", 0, sczTempFile))
-        {
-            PathExitWithLastError(hr, "Failed to create new temp file name.");
-        }
+        hr = PathGetTempFileName(sczTempPath, wzPrefix, 0, &sczTempFile);
+        PathExitOnFailure(hr, "Failed to create new temp file name.");
 
         hTempFile = ::CreateFileW(sczTempFile, GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_DELETE, NULL, OPEN_EXISTING, dwFileAttributes, NULL);
         if (INVALID_HANDLE_VALUE == hTempFile)
@@ -684,6 +707,82 @@ LExit:
 }
 
 
+DAPI_(HRESULT) PathGetTempFileName(
+    __in LPCWSTR wzPathName,
+    __in LPCWSTR wzPrefixString,
+    __in UINT uUnique,
+    __out LPWSTR* psczTempFileName
+    )
+{
+    HRESULT hr = S_OK;
+    size_t cchFullPath = 0;
+    WORD wValue = (WORD)(0xffff & uUnique);
+    LPWSTR scz = NULL;
+    LPWSTR sczTempFile = NULL;
+    HANDLE hTempFile = INVALID_HANDLE_VALUE;
+
+    hr = ::StringCchLengthW(wzPathName, STRSAFE_MAX_CCH, &cchFullPath);
+    PathExitOnFailure(hr, "Failed to get length of path to prefix.");
+
+    if (MAX_PATH - 14 >= cchFullPath)
+    {
+        hr = StrAlloc(psczTempFileName, MAX_PATH);
+        PathExitOnFailure(hr, "Failed to allocate buffer for GetTempFileNameW.");
+
+        if (!::GetTempFileNameW(wzPathName, wzPrefixString, uUnique, *psczTempFileName))
+        {
+            PathExitWithLastError(hr, "Failed to create new temp file name.");
+        }
+
+        ExitFunction();
+    }
+
+    // TODO: when uUnique is 0, consider not always starting at 0 to avoid collisions if this is called repeatedly.
+    // Purposely let it wrap around.
+    for (WORD w = 0; w < WORD_MAX && INVALID_HANDLE_VALUE == hTempFile; ++wValue)
+    {
+        hr = StrAllocFormatted(&scz, L"%ls%x.TMP", wzPrefixString, w);
+        PathExitOnFailure(hr, "Failed to allocate memory for file template.");
+
+        hr = PathConcat(wzPathName, scz, &sczTempFile);
+        PathExitOnFailure(hr, "Failed to allocate temp file name.");
+
+        hTempFile = ::CreateFileW(sczTempFile, GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_DELETE, NULL, CREATE_NEW, 0, NULL);
+        if (INVALID_HANDLE_VALUE == hTempFile)
+        {
+            // if the file already exists, try next one.
+            hr = HRESULT_FROM_WIN32(::GetLastError());
+            if (HRESULT_FROM_WIN32(ERROR_FILE_EXISTS) == hr)
+            {
+                hr = S_OK;
+            }
+            PathExitOnFailure(hr, "Failed to create file: %ls", sczTempFile);
+        }
+
+        ++w;
+    }
+
+    if (INVALID_HANDLE_VALUE == hTempFile)
+    {
+        PathExitWithRootFailure(hr, HRESULT_FROM_WIN32(ERROR_FILE_EXISTS), "Failed to create temp file.");
+    }
+
+    hr = StrAllocString(psczTempFileName, sczTempFile, 0);
+    PathExitOnFailure(hr, "Failed to copy temp file string.");
+
+LExit:
+    if (INVALID_HANDLE_VALUE != hTempFile)
+    {
+        ::CloseHandle(hTempFile);
+    }
+
+    ReleaseStr(scz);
+    ReleaseStr(sczTempFile);
+
+    return hr;
+}
+
+
 DAPI_(HRESULT) PathCreateTimeBasedTempFile(
     __in_z_opt LPCWSTR wzDirectory,
     __in_z LPCWSTR wzPrefix,
@@ -695,7 +794,7 @@ DAPI_(HRESULT) PathCreateTimeBasedTempFile(
 {
     HRESULT hr = S_OK;
     BOOL fRetry = FALSE;
-    WCHAR wzTempPath[MAX_PATH] = { };
+    LPWSTR sczTempParentPath = NULL;
     LPWSTR sczPrefix = NULL;
     LPWSTR sczPrefixFolder = NULL;
     SYSTEMTIME time = { };
@@ -711,12 +810,10 @@ DAPI_(HRESULT) PathCreateTimeBasedTempFile(
     }
     else
     {
-        if (!::GetTempPathW(countof(wzTempPath), wzTempPath))
-        {
-            PathExitWithLastError(hr, "Failed to get temp folder.");
-        }
+        hr = PathGetTempPath(&sczTempParentPath, NULL);
+        PathExitOnFailure(hr, "Failed to get temp folder.");
 
-        hr = PathConcat(wzTempPath, wzPrefix, &sczPrefix);
+        hr = PathConcat(sczTempParentPath, wzPrefix, &sczPrefix);
         PathExitOnFailure(hr, "Failed to concatenate the temp folder and log prefix.");
     }
 
@@ -778,6 +875,7 @@ DAPI_(HRESULT) PathCreateTimeBasedTempFile(
 
 LExit:
     ReleaseFile(hTempFile);
+    ReleaseStr(sczTempParentPath);
     ReleaseStr(sczTempPath);
     ReleaseStr(sczPrefixFolder);
     ReleaseStr(sczPrefix);
@@ -799,7 +897,6 @@ DAPI_(HRESULT) PathCreateTempDirectory(
     HRESULT hr = S_OK;
 
     LPWSTR sczTempPath = NULL;
-    DWORD cchTempPath = MAX_PATH;
 
     LPWSTR scz = NULL;
 
@@ -813,13 +910,8 @@ DAPI_(HRESULT) PathCreateTempDirectory(
     }
     else
     {
-        hr = StrAlloc(&sczTempPath, cchTempPath);
-        PathExitOnFailure(hr, "Failed to allocate memory for the temp path.");
-
-        if (!::GetTempPathW(cchTempPath, sczTempPath))
-        {
-            PathExitWithLastError(hr, "Failed to get temp path.");
-        }
+        hr = PathGetTempPath(&sczTempPath, NULL);
+        PathExitOnFailure(hr, "Failed to get temp path.");
     }
 
     for (DWORD i = 1; i <= dwUniqueCount; ++i)
@@ -869,46 +961,230 @@ LExit:
 
 
 DAPI_(HRESULT) PathGetTempPath(
-    __out_z LPWSTR* psczTempPath
+    __out_z LPWSTR* psczTempPath,
+    __out_opt SIZE_T* pcch
+    )
+{
+
+    HRESULT hr = S_OK;
+    SIZE_T cchMax = 0;
+    DWORD cchBuffer = 0;
+    DWORD cch = 0;
+    DWORD dwAttempts = 0;
+    HMODULE hModule = NULL;
+    PFN_GETTEMPPATH2W pfnGetTempPath = NULL;
+    const DWORD dwMaxAttempts = 10;
+
+    if (*psczTempPath)
+    {
+        hr = StrMaxLength(*psczTempPath, &cchMax);
+        PathExitOnFailure(hr, "Failed to get max length of input buffer.");
+
+        cchBuffer = (DWORD)min(DWORD_MAX, cchMax);
+    }
+    else
+    {
+        cchBuffer = MAX_PATH + 1;
+
+        hr = StrAlloc(psczTempPath, cchBuffer);
+        PathExitOnFailure(hr, "Failed to allocate space for temp path.");
+    }
+
+    hr = LoadSystemLibrary(L"kernel32.dll", &hModule);
+    PathExitOnFailure(hr, "Failed to load kernel32.dll");
+
+    pfnGetTempPath = reinterpret_cast<PFN_GETTEMPPATH2W>(::GetProcAddress(hModule, "GetTempPath2W"));
+    if (!pfnGetTempPath)
+    {
+        pfnGetTempPath = ::GetTempPathW;
+    }
+
+    for (; dwAttempts < dwMaxAttempts; ++dwAttempts)
+    {
+        cch = pfnGetTempPath(cchBuffer, *psczTempPath);
+        PathExitOnNullWithLastError(cch, hr, "Failed to get temp path.");
+
+        cch += 1; // add one for null terminator.
+
+        if (cch <= cchBuffer)
+        {
+            break;
+        }
+
+        hr = StrAlloc(psczTempPath, cch);
+        PathExitOnFailure(hr, "Failed to reallocate space for temp path.");
+
+        cchBuffer = cch;
+    }
+
+    if (dwMaxAttempts == dwAttempts)
+    {
+        PathExitWithRootFailure(hr, E_INSUFFICIENT_BUFFER, "GetTempPathW results never converged.");
+    }
+
+    if (pcch)
+    {
+        *pcch = cch - 1; // remove one for null terminator.
+    }
+
+LExit:
+    return hr;
+}
+
+
+DAPI_(HRESULT) PathGetSystemDirectory(
+    __out_z LPWSTR* psczSystemPath
+    )
+{
+    HRESULT hr = S_OK;
+    SIZE_T cchMax = 0;
+    DWORD cchBuffer = 0;
+    DWORD cch = 0;
+
+    if (*psczSystemPath)
+    {
+        hr = StrMaxLength(*psczSystemPath, &cchMax);
+        PathExitOnFailure(hr, "Failed to get max length of input buffer.");
+
+        cchBuffer = (DWORD)min(DWORD_MAX, cchMax);
+    }
+    else
+    {
+        cchBuffer = MAX_PATH + 1;
+
+        hr = StrAlloc(psczSystemPath, cchBuffer);
+        PathExitOnFailure(hr, "Failed to allocate space for system directory.");
+    }
+
+    cch = ::GetSystemDirectoryW(*psczSystemPath, cchBuffer);
+    PathExitOnNullWithLastError(cch, hr, "Failed to get system directory path with default size.");
+
+    if (cch > cchBuffer)
+    {
+        hr = StrAlloc(psczSystemPath, cch);
+        PathExitOnFailure(hr, "Failed to realloc system directory path.");
+
+        cchBuffer = cch;
+
+        cch = ::GetSystemDirectoryW(*psczSystemPath, cchBuffer);
+        PathExitOnNullWithLastError(cch, hr, "Failed to get system directory path with returned size.");
+
+        if (cch > cchBuffer)
+        {
+            PathExitWithRootFailure(hr, E_INSUFFICIENT_BUFFER, "Failed to get system directory path with returned size.");
+        }
+    }
+
+    hr = PathBackslashTerminate(psczSystemPath);
+    PathExitOnFailure(hr, "Failed to terminate system directory path with backslash.");
+
+LExit:
+    return hr;
+}
+
+
+DAPI_(HRESULT) PathGetSystemWow64Directory(
+    __out_z LPWSTR* psczSystemPath
     )
 {
     HRESULT hr = S_OK;
-    WCHAR wzTempPath[MAX_PATH + 1] = { };
+    SIZE_T cchMax = 0;
+    DWORD cchBuffer = 0;
     DWORD cch = 0;
 
-    cch = ::GetTempPathW(countof(wzTempPath), wzTempPath);
-    if (!cch)
+    if (*psczSystemPath)
     {
-        PathExitWithLastError(hr, "Failed to GetTempPath.");
+        hr = StrMaxLength(*psczSystemPath, &cchMax);
+        PathExitOnFailure(hr, "Failed to get max length of input buffer.");
+
+        cchBuffer = (DWORD)min(DWORD_MAX, cchMax);
     }
-    else if (cch >= countof(wzTempPath))
+    else
     {
-        PathExitWithRootFailure(hr, E_INSUFFICIENT_BUFFER, "TEMP directory path too long.");
+        cchBuffer = MAX_PATH + 1;
+
+        hr = StrAlloc(psczSystemPath, cchBuffer);
+        PathExitOnFailure(hr, "Failed to allocate space for system wow64 directory.");
     }
 
-    hr = StrAllocString(psczTempPath, wzTempPath, cch);
-    PathExitOnFailure(hr, "Failed to copy TEMP directory path.");
+    cch = ::GetSystemWow64DirectoryW(*psczSystemPath, cchBuffer);
+    PathExitOnNullWithLastError(cch, hr, "Failed to get system wow64 directory path with default size.");
+
+    cch += 1; // add one for the null terminator.
+
+    if (cch > cchBuffer)
+    {
+        hr = StrAlloc(psczSystemPath, cch);
+        PathExitOnFailure(hr, "Failed to realloc system wow64 directory path.");
+
+        cchBuffer = cch;
+
+        cch = ::GetSystemWow64DirectoryW(*psczSystemPath, cchBuffer);
+        PathExitOnNullWithLastError(cch, hr, "Failed to get system wow64 directory path with returned size.");
+
+        cch += 1; // add one for the null terminator.
+
+        if (cch > cchBuffer)
+        {
+            PathExitWithRootFailure(hr, E_INSUFFICIENT_BUFFER, "Failed to get system wow64 directory path with returned size.");
+        }
+    }
+
+    hr = PathBackslashTerminate(psczSystemPath);
+    PathExitOnFailure(hr, "Failed to terminate system wow64 directory path with backslash.");
 
 LExit:
     return hr;
 }
 
 
-DAPI_(HRESULT) PathGetKnownFolder(
-    __in int csidl,
-    __out LPWSTR* psczKnownFolder
+DAPI_(HRESULT) PathGetVolumePathName(
+    __in_z LPCWSTR wzFileName,
+    __out_z LPWSTR* psczVolumePathName
     )
 {
     HRESULT hr = S_OK;
+    DWORD cchBuffer = 0;
+    SIZE_T cchMax = 0;
+    const DWORD dwMaxAttempts = 20;
 
-    hr = StrAlloc(psczKnownFolder, MAX_PATH);
-    PathExitOnFailure(hr, "Failed to allocate memory for known folder.");
+    if (*psczVolumePathName)
+    {
+        hr = StrMaxLength(*psczVolumePathName, &cchMax);
+        PathExitOnFailure(hr, "Failed to get max length of input buffer.");
 
-    hr = ::SHGetFolderPathW(NULL, csidl, NULL, SHGFP_TYPE_CURRENT, *psczKnownFolder);
-    PathExitOnFailure(hr, "Failed to get known folder path.");
+        cchBuffer = (DWORD)min(DWORD_MAX, cchMax);
+    }
+    else
+    {
+        cchBuffer = MAX_PATH + 1;
+
+        hr = StrAlloc(psczVolumePathName, cchBuffer);
+        PathExitOnFailure(hr, "Failed to allocate space for volume path name.");
+    }
+
+    for (DWORD i = 0; i < dwMaxAttempts; ++i)
+    {
+        if (::GetVolumePathNameW(wzFileName, *psczVolumePathName, cchBuffer))
+        {
+            break;
+        }
+
+        hr = HRESULT_FROM_WIN32(::GetLastError());
+        if (HRESULT_FROM_WIN32(ERROR_FILENAME_EXCED_RANGE) != hr && E_INSUFFICIENT_BUFFER != hr ||
+            (dwMaxAttempts - 1) == i)
+        {
+            PathExitWithRootFailure(hr, hr, "Failed to get volume path name of: %ls", wzFileName);
+        }
+
+        cchBuffer *= 2;
+
+        hr = StrAlloc(psczVolumePathName, cchBuffer);
+        PathExitOnFailure(hr, "Failed to re-allocate more space for volume path name.");
+    }
 
-    hr = PathBackslashTerminate(psczKnownFolder);
-    PathExitOnFailure(hr, "Failed to ensure known folder path is backslash terminated.");
+    hr = PathBackslashTerminate(psczVolumePathName);
+    PathExitOnFailure(hr, "Failed to terminate volume path name with backslash.");
 
 LExit:
     return hr;
diff --git a/src/libs/dutil/WixToolset.DUtil/rexutil.cpp b/src/libs/dutil/WixToolset.DUtil/rexutil.cpp
index 155ca714..ce28beb3 100644
--- a/src/libs/dutil/WixToolset.DUtil/rexutil.cpp
+++ b/src/libs/dutil/WixToolset.DUtil/rexutil.cpp
@@ -28,7 +28,7 @@ static ERF verf;
 static FAKE_FILE vrgffFileTable[FILETABLESIZE];
 static DWORD vcbRes;
 static LPCBYTE vpbRes;
-static CHAR vszResource[MAX_PATH];
+static LPSTR vpszResource = NULL;
 static REX_CALLBACK_WRITE vpfnWrite = NULL;
 
 static HRESULT vhrLastError = S_OK;
@@ -85,6 +85,8 @@ LExit:
     {
         ::FDIDestroy(vhfdi);
         vhfdi = NULL;
+
+        ReleaseNullStr(vpszResource);
     }
     
     return hr;
@@ -101,6 +103,8 @@ extern "C" void RexUninitialize()
     {
         ::FDIDestroy(vhfdi);
         vhfdi = NULL;
+
+        ReleaseNullStr(vpszResource);
     }
 }
 
@@ -124,12 +128,12 @@ extern "C" HRESULT RexExtract(
 {
     Assert(vhfdi);
     HRESULT hr = S_OK;
-    BOOL fResult;
+    BOOL fResult = FALSE;
 
     HRSRC hResInfo = NULL;
     HANDLE hRes = NULL;
 
-    REX_CALLBACK_STRUCT rcs;
+    REX_CALLBACK_STRUCT rcs = { };
 
     // remember the write callback
     vpfnWrite = pfnWrite;
@@ -158,7 +162,7 @@ extern "C" HRESULT RexExtract(
     //    RexExitOnLastError(hr, "failed to convert cabinet resource name to ASCII: %ls", wzResource);
     //}
 
-    hr = ::StringCchCopyA(vszResource, countof(vszResource), szResource);
+    hr = StrAnsiAllocStringAnsi(&vpszResource, szResource, 0);
     RexExitOnFailure(hr, "Failed to copy resource name to global.");
 
     //
@@ -171,7 +175,7 @@ extern "C" HRESULT RexExtract(
     rcs.pfnProgress = pfnProgress;
     rcs.pvContext = pvContext;
 
-    fResult = ::FDICopy(vhfdi, vszResource, "", 0, RexCallback, NULL, static_cast<void*>(&rcs));
+    fResult = ::FDICopy(vhfdi, vpszResource, "", 0, RexCallback, NULL, static_cast<void*>(&rcs));
     if (!fResult && !rcs.fStopExtracting)   // if something went wrong and it wasn't us just stopping the extraction, then return a failure
     {
         hr = vhrLastError;  // TODO: put verf info in trace message here
@@ -227,7 +231,7 @@ static __callback INT_PTR FAR DIAMONDAPI RexOpen(__in_z char FAR *pszFile, int o
         RexExitOnFailure(hr, "File table exceeded");
     }
 
-    if (0 == lstrcmpA(vszResource, pszFile))
+    if (0 == lstrcmpA(vpszResource, pszFile))
     {
         vrgffFileTable[i].fUsed = TRUE;
         vrgffFileTable[i].fftType = MEMORY_FILE;
@@ -436,15 +440,16 @@ static __callback INT_PTR DIAMONDAPI RexCallback(FDINOTIFICATIONTYPE iNotificati
     HANDLE hFile = INVALID_HANDLE_VALUE;
 
     REX_CALLBACK_STRUCT* prcs = static_cast<REX_CALLBACK_STRUCT*>(pFDINotify->pv);
-    LPCSTR sz;
-    WCHAR wz[MAX_PATH];
-    FILETIME ft;
+    LPCSTR sz = NULL;
+    LPWSTR pwz = NULL;
+    LPWSTR pwzPath = NULL;
+    FILETIME ft = { };
     int i = 0;
 
     switch (iNotification)
     {
     case fdintCOPY_FILE:  // beGIN extracting a resource from cabinet
-        Assert(pFDINotify->psz1);
+        Assert(pFDINotify->psz1 && prcs);
 
         if (prcs->fStopExtracting)
         {
@@ -453,55 +458,50 @@ static __callback INT_PTR DIAMONDAPI RexCallback(FDINOTIFICATIONTYPE iNotificati
 
         // convert params to useful variables
         sz = static_cast<LPCSTR>(pFDINotify->psz1);
-        if (!::MultiByteToWideChar(CP_ACP, 0, sz, -1, wz, countof(wz)))
-        {
-            RexExitWithLastError(hr, "failed to convert cabinet file id to unicode: %s", sz);
-        }
+        RexExitOnNull(sz, hr, E_INVALIDARG, "No cabinet file ID given to convert");
+
+        hr = StrAllocStringAnsi(&pwz, sz, 0, CP_ACP);
+        RexExitOnFailure(hr, "failed to convert cabinet file id to unicode: %hs", sz);
 
         if (prcs->pfnProgress)
         {
-            hr = prcs->pfnProgress(TRUE, wz, prcs->pvContext);
+            hr = prcs->pfnProgress(TRUE, pwz, prcs->pvContext);
             if (S_OK != hr)
             {
                 ExitFunction();
             }
         }
 
-        if (L'*' == *prcs->pwzExtract || 0 == lstrcmpW(prcs->pwzExtract, wz))
+        if (L'*' == *prcs->pwzExtract || 0 == lstrcmpW(prcs->pwzExtract, pwz))
         {
             // get the created date for the resource in the cabinet
             if (!::DosDateTimeToFileTime(pFDINotify->date, pFDINotify->time, &ft))
             {
-                RexExitWithLastError(hr, "failed to get time for resource: %ls", wz);
+                RexExitWithLastError(hr, "failed to get time for resource: %ls", pwz);
             }
 
-            WCHAR wzPath[MAX_PATH];
-
-            hr = ::StringCchCopyW(wzPath, countof(wzPath), prcs->pwzExtractDir);
-            RexExitOnFailure(hr, "failed to copy extract directory: %ls for file: %ls", prcs->pwzExtractDir, wz);
-
             if (L'*' == *prcs->pwzExtract)
             {
-                hr = ::StringCchCatW(wzPath, countof(wzPath), wz);
-                RexExitOnFailure(hr, "failed to concat onto path: %ls file: %ls", wzPath, wz);
+                hr = PathConcat(prcs->pwzExtractDir, pwz, &pwzPath);
+                RexExitOnFailure(hr, "failed to concat onto path: %ls file: %ls", prcs->pwzExtractDir, pwz);
             }
             else
             {
                 Assert(*prcs->pwzExtractName);
 
-                hr = ::StringCchCatW(wzPath, countof(wzPath), prcs->pwzExtractName);
-                RexExitOnFailure(hr, "failed to concat onto path: %ls file: %ls", wzPath, prcs->pwzExtractName);
+                hr = PathConcat(prcs->pwzExtractDir, prcs->pwzExtractName, &pwzPath);
+                RexExitOnFailure(hr, "failed to concat onto path: %ls file: %ls", prcs->pwzExtractDir, prcs->pwzExtractName);
             }
 
             // Quickly chop off the file name part of the path to ensure the path exists
             // then put the file name back on the path (by putting the first character
             // back over the null terminator).
-            LPWSTR wzFile = PathFile(wzPath);
+            LPWSTR wzFile = PathFile(pwzPath);
             WCHAR wzFileFirstChar = *wzFile;
             *wzFile = L'\0';
 
-            hr = DirEnsureExists(wzPath, NULL);
-            RexExitOnFailure(hr, "failed to ensure directory: %ls", wzPath);
+            hr = DirEnsureExists(pwzPath, NULL);
+            RexExitOnFailure(hr, "failed to ensure directory: %ls", pwzPath);
 
             hr = S_OK;
 
@@ -524,10 +524,10 @@ static __callback INT_PTR DIAMONDAPI RexCallback(FDINOTIFICATIONTYPE iNotificati
             }
 
             // open the file
-            hFile = ::CreateFileW(wzPath, GENERIC_WRITE, FILE_SHARE_READ, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
+            hFile = ::CreateFileW(pwzPath, GENERIC_WRITE, FILE_SHARE_READ, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
             if (INVALID_HANDLE_VALUE == hFile)
             {
-                RexExitWithLastError(hr, "failed to open file: %ls", wzPath);
+                RexExitWithLastError(hr, "failed to open file: %ls", pwzPath);
             }
 
             vrgffFileTable[i].fUsed = TRUE;
@@ -554,20 +554,20 @@ static __callback INT_PTR DIAMONDAPI RexCallback(FDINOTIFICATIONTYPE iNotificati
 
         break;
     case fdintCLOSE_FILE_INFO:  // resource extraction complete
-        Assert(pFDINotify->hf && pFDINotify->psz1);
+        Assert(pFDINotify->hf && prcs && pFDINotify->psz1);
 
         // convert params to useful variables
         sz = static_cast<LPCSTR>(pFDINotify->psz1);
-        if (!::MultiByteToWideChar(CP_ACP, 0, sz, -1, wz, countof(wz)))
-        {
-            RexExitWithLastError(hr, "failed to convert cabinet file id to unicode: %s", sz);
-        }
+        RexExitOnNull(sz, hr, E_INVALIDARG, "No cabinet file ID given to convert");
+
+        hr = StrAllocStringAnsi(&pwz, sz, 0, CP_ACP);
+        RexExitOnFailure(hr, "failed to convert cabinet file id to unicode: %hs", sz);
 
         RexClose(pFDINotify->hf);
 
         if (prcs->pfnProgress)
         {
-            hr = prcs->pfnProgress(FALSE, wz, prcs->pvContext);
+            hr = prcs->pfnProgress(FALSE, pwz, prcs->pvContext);
         }
 
         if (S_OK == hr && L'*' == *prcs->pwzExtract)   // if everything is okay and we're extracting all files, keep going
@@ -597,5 +597,8 @@ LExit:
         vhrLastError = hr;
     }
 
+    ReleaseStr(pwz);
+    ReleaseStr(pwzPath);
+
     return (S_OK == hr) ? ipResult : -1;
 }
diff --git a/src/libs/dutil/WixToolset.DUtil/sceutil.cpp b/src/libs/dutil/WixToolset.DUtil/sceutil.cpp
index 4eede74f..590c937a 100644
--- a/src/libs/dutil/WixToolset.DUtil/sceutil.cpp
+++ b/src/libs/dutil/WixToolset.DUtil/sceutil.cpp
@@ -317,7 +317,7 @@ extern "C" HRESULT DAPI SceOpenDatabase(
 {
     HRESULT hr = S_OK;
     DWORD dwVersionFound = 0;
-    WCHAR wzTempDbFile[MAX_PATH];
+    LPWSTR sczTempDbFile = NULL;
     LPCWSTR wzPathToOpen = NULL;
     LPWSTR sczSchemaType = NULL;
     SCE_DATABASE *pNewSceDatabase = NULL;
@@ -343,16 +343,16 @@ extern "C" HRESULT DAPI SceOpenDatabase(
     // TODO: had trouble getting SQL CE to read a file read-only, so we're copying it to a temp path for now.
     if (fReadOnly)
     {
-        hr = DirCreateTempPath(PathFile(sczFile), (LPWSTR)wzTempDbFile, _countof(wzTempDbFile));
+        hr = DirCreateTempPath(PathFile(sczFile), &sczTempDbFile);
         ExitOnFailure(hr, "Failed to get temp path");
 
-        hr = FileEnsureCopy(sczFile, (LPCWSTR)wzTempDbFile, TRUE);
+        hr = FileEnsureCopy(sczFile, sczTempDbFile, TRUE);
         ExitOnFailure(hr, "Failed to copy file to temp path");
 
-        hr = StrAllocString(&pNewSceDatabaseInternal->sczTempDbFile, (LPCWSTR)wzTempDbFile, 0);
+        hr = StrAllocString(&pNewSceDatabaseInternal->sczTempDbFile, sczTempDbFile, 0);
         ExitOnFailure(hr, "Failed to copy temp db file path");
 
-        wzPathToOpen = (LPCWSTR)wzTempDbFile;
+        wzPathToOpen = sczTempDbFile;
     }
     else
     {
@@ -424,6 +424,7 @@ extern "C" HRESULT DAPI SceOpenDatabase(
 LExit:
     ReleaseBSTR(rgdbpDataSourceProp[0].vValue.bstrVal);
     ReleaseStr(sczSchemaType);
+    ReleaseStr(sczTempDbFile);
     ReleaseDatabase(pNewSceDatabase);
 
     return hr;
diff --git a/src/libs/dutil/WixToolset.DUtil/shelutil.cpp b/src/libs/dutil/WixToolset.DUtil/shelutil.cpp
index 2eb9a52a..72a0e5ce 100644
--- a/src/libs/dutil/WixToolset.DUtil/shelutil.cpp
+++ b/src/libs/dutil/WixToolset.DUtil/shelutil.cpp
@@ -9,6 +9,7 @@
 #define ShelExitWithLastError(x, s, ...) ExitWithLastErrorSource(DUTIL_SOURCE_SHELUTIL, x, s, __VA_ARGS__)
 #define ShelExitOnFailure(x, s, ...) ExitOnFailureSource(DUTIL_SOURCE_SHELUTIL, x, s, __VA_ARGS__)
 #define ShelExitOnRootFailure(x, s, ...) ExitOnRootFailureSource(DUTIL_SOURCE_SHELUTIL, x, s, __VA_ARGS__)
+#define ShelExitWithRootFailure(x, e, s, ...) ExitWithRootFailureSource(DUTIL_SOURCE_SHELUTIL, x, e, s, __VA_ARGS__)
 #define ShelExitOnFailureDebugTrace(x, s, ...) ExitOnFailureDebugTraceSource(DUTIL_SOURCE_SHELUTIL, x, s, __VA_ARGS__)
 #define ShelExitOnNull(p, x, e, s, ...) ExitOnNullSource(DUTIL_SOURCE_SHELUTIL, p, x, e, s, __VA_ARGS__)
 #define ShelExitOnNullWithLastError(p, x, s, ...) ExitOnNullWithLastErrorSource(DUTIL_SOURCE_SHELUTIL, p, x, s, __VA_ARGS__)
@@ -19,6 +20,10 @@
 
 static PFN_SHELLEXECUTEEXW vpfnShellExecuteExW = ::ShellExecuteExW;
 
+static HRESULT DAPI GetFolderFromCsidl(
+    __out_z LPWSTR* psczFolderPath,
+    __in int csidlFolder
+    );
 static HRESULT GetDesktopShellView(
     __in REFIID riid,
     __out void **ppv
@@ -57,7 +62,14 @@ extern "C" HRESULT DAPI ShelExec(
     )
 {
     HRESULT hr = S_OK;
-    SHELLEXECUTEINFOW shExecInfo = {};
+    SHELLEXECUTEINFOW shExecInfo = { };
+    size_t cchWorkingDirectory = 0;
+
+    // CreateProcessW has undocumented MAX_PATH restriction for lpCurrentDirectory even when long path support is enabled.
+    if (wzWorkingDirectory && FAILED(::StringCchLengthW(wzWorkingDirectory, MAX_PATH - 1, &cchWorkingDirectory)))
+    {
+        wzWorkingDirectory = NULL;
+    }
 
     shExecInfo.cbSize = sizeof(SHELLEXECUTEINFO);
     shExecInfo.fMask = SEE_MASK_FLAG_DDEWAIT | SEE_MASK_FLAG_NO_UI | SEE_MASK_NOCLOSEPROCESS;
@@ -159,11 +171,7 @@ LExit:
 }
 
 
-/********************************************************************
- ShelGetFolder() - gets a folder by CSIDL.
-
-*******************************************************************/
-extern "C" HRESULT DAPI ShelGetFolder(
+static HRESULT DAPI GetFolderFromCsidl(
     __out_z LPWSTR* psczFolderPath,
     __in int csidlFolder
     )
@@ -185,19 +193,6 @@ LExit:
 }
 
 
-/********************************************************************
- ShelGetKnownFolder() - gets a folder by KNOWNFOLDERID.
-
- Note: return E_NOTIMPL if called on pre-Vista operating systems.
-*******************************************************************/
-#ifndef REFKNOWNFOLDERID
-#define REFKNOWNFOLDERID REFGUID
-#endif
-
-#ifndef KF_FLAG_CREATE
-#define KF_FLAG_CREATE              0x00008000  // Make sure that the folder already exists or create it and apply security specified in folder definition
-#endif
-
 EXTERN_C typedef HRESULT (STDAPICALLTYPE *PFN_SHGetKnownFolderPath)(
     REFKNOWNFOLDERID rfid,
     DWORD dwFlags,
@@ -249,6 +244,181 @@ LExit:
     return hr;
 }
 
+extern "C" HRESULT DAPI ShelGetFolder(
+    __out_z LPWSTR* psczFolderPath,
+    __in int csidlFolder
+    )
+{
+    HRESULT hr = S_OK;
+    LPWSTR sczPath = NULL;
+    KNOWNFOLDERID rfid = { };
+
+    csidlFolder &= ~CSIDL_FLAG_MASK;
+
+    switch (csidlFolder)
+    {
+    case CSIDL_ADMINTOOLS:
+        rfid = FOLDERID_AdminTools;
+        break;
+    case CSIDL_APPDATA:
+        rfid = FOLDERID_RoamingAppData;
+        break;
+    case CSIDL_CDBURN_AREA:
+        rfid = FOLDERID_CDBurning;
+        break;
+    case CSIDL_COMMON_ADMINTOOLS:
+        rfid = FOLDERID_CommonAdminTools;
+        break;
+    case CSIDL_COMMON_APPDATA:
+        rfid = FOLDERID_ProgramData;
+        break;
+    case CSIDL_COMMON_DESKTOPDIRECTORY:
+        rfid = FOLDERID_PublicDesktop;
+        break;
+    case CSIDL_COMMON_DOCUMENTS:
+        rfid = FOLDERID_PublicDocuments;
+        break;
+    case CSIDL_COMMON_MUSIC:
+        rfid = FOLDERID_PublicMusic;
+        break;
+    case CSIDL_COMMON_OEM_LINKS:
+        rfid = FOLDERID_CommonOEMLinks;
+        break;
+    case CSIDL_COMMON_PICTURES:
+        rfid = FOLDERID_PublicPictures;
+        break;
+    case CSIDL_COMMON_PROGRAMS:
+        rfid = FOLDERID_CommonPrograms;
+        break;
+    case CSIDL_COMMON_STARTMENU:
+        rfid = FOLDERID_CommonStartMenu;
+        break;
+    case CSIDL_COMMON_STARTUP: __fallthrough;
+    case CSIDL_COMMON_ALTSTARTUP:
+        rfid = FOLDERID_CommonStartup;
+        break;
+    case CSIDL_COMMON_TEMPLATES:
+        rfid = FOLDERID_CommonTemplates;
+        break;
+    case CSIDL_COMMON_VIDEO:
+        rfid = FOLDERID_PublicVideos;
+        break;
+    case CSIDL_COOKIES:
+        rfid = FOLDERID_Cookies;
+        break;
+    case CSIDL_DESKTOP:
+    case CSIDL_DESKTOPDIRECTORY:
+        rfid = FOLDERID_Desktop;
+        break;
+    case CSIDL_FAVORITES: __fallthrough;
+    case CSIDL_COMMON_FAVORITES:
+        rfid = FOLDERID_Favorites;
+        break;
+    case CSIDL_FONTS:
+        rfid = FOLDERID_Fonts;
+        break;
+    case CSIDL_HISTORY:
+        rfid = FOLDERID_History;
+        break;
+    case CSIDL_INTERNET_CACHE:
+        rfid = FOLDERID_InternetCache;
+        break;
+    case CSIDL_LOCAL_APPDATA:
+        rfid = FOLDERID_LocalAppData;
+        break;
+    case CSIDL_MYMUSIC:
+        rfid = FOLDERID_Music;
+        break;
+    case CSIDL_MYPICTURES:
+        rfid = FOLDERID_Pictures;
+        break;
+    case CSIDL_MYVIDEO:
+        rfid = FOLDERID_Videos;
+        break;
+    case CSIDL_NETHOOD:
+        rfid = FOLDERID_NetHood;
+        break;
+    case CSIDL_PERSONAL:
+        rfid = FOLDERID_Documents;
+        break;
+    case CSIDL_PRINTHOOD:
+        rfid = FOLDERID_PrintHood;
+        break;
+    case CSIDL_PROFILE:
+        rfid = FOLDERID_Profile;
+        break;
+    case CSIDL_PROGRAM_FILES:
+        rfid = FOLDERID_ProgramFiles;
+        break;
+    case CSIDL_PROGRAM_FILESX86:
+        rfid = FOLDERID_ProgramFilesX86;
+        break;
+    case CSIDL_PROGRAM_FILES_COMMON:
+        rfid = FOLDERID_ProgramFilesCommon;
+        break;
+    case CSIDL_PROGRAM_FILES_COMMONX86:
+        rfid = FOLDERID_ProgramFilesCommonX86;
+        break;
+    case CSIDL_PROGRAMS:
+        rfid = FOLDERID_Programs;
+        break;
+    case CSIDL_RECENT:
+        rfid = FOLDERID_Recent;
+        break;
+    case CSIDL_RESOURCES:
+        rfid = FOLDERID_ResourceDir;
+        break;
+    case CSIDL_RESOURCES_LOCALIZED:
+        rfid = FOLDERID_LocalizedResourcesDir;
+        break;
+    case CSIDL_SENDTO:
+        rfid = FOLDERID_SendTo;
+        break;
+    case CSIDL_STARTMENU:
+        rfid = FOLDERID_StartMenu;
+        break;
+    case CSIDL_STARTUP:
+    case CSIDL_ALTSTARTUP:
+        rfid = FOLDERID_Startup;
+        break;
+    case CSIDL_SYSTEM:
+        rfid = FOLDERID_System;
+        break;
+    case CSIDL_SYSTEMX86:
+        rfid = FOLDERID_SystemX86;
+        break;
+    case CSIDL_TEMPLATES:
+        rfid = FOLDERID_Templates;
+        break;
+    case CSIDL_WINDOWS:
+        rfid = FOLDERID_Windows;
+        break;
+    default:
+        ShelExitWithRootFailure(hr, E_INVALIDARG, "Unknown csidl: %d", csidlFolder);
+    }
+
+    hr = ShelGetKnownFolder(&sczPath, rfid);
+    if (E_NOTIMPL == hr)
+    {
+        hr = S_FALSE;
+    }
+    ShelExitOnFailure(hr, "Failed to get known folder.");
+
+    if (S_FALSE == hr)
+    {
+        hr = GetFolderFromCsidl(&sczPath, csidlFolder);
+        ShelExitOnFailure(hr, "Failed to get csidl folder.");
+    }
+
+    *psczFolderPath = sczPath;
+    sczPath = NULL;
+
+LExit:
+    ReleaseStr(sczPath);
+
+    return hr;
+}
+
 
 // Internal functions.
 
@@ -287,7 +457,7 @@ static HRESULT GetDesktopShellView(
     else if (S_FALSE == hr)
     {
         //Windows XP
-        hr = SHGetDesktopFolder(&psf);
+        hr = ::SHGetDesktopFolder(&psf);
         ShelExitOnFailure(hr, "Failed to get desktop folder.");
 
         hr = psf->CreateViewObject(NULL, IID_IShellView, ppv);
diff --git a/src/libs/dutil/test/DUtilUnitTest/PathUtilTest.cpp b/src/libs/dutil/test/DUtilUnitTest/PathUtilTest.cpp
index e9ef1047..109c558c 100644
--- a/src/libs/dutil/test/DUtilUnitTest/PathUtilTest.cpp
+++ b/src/libs/dutil/test/DUtilUnitTest/PathUtilTest.cpp
@@ -7,6 +7,11 @@ using namespace System::IO;
 using namespace Xunit;
 using namespace WixBuildTools::TestSupport;
 
+// from PathCch.h
+#ifndef PATHCCH_ALLOW_LONG_PATHS
+#define PATHCCH_ALLOW_LONG_PATHS       0x01
+#endif
+
 namespace DutilTests
 {
     public ref class PathUtil
@@ -102,18 +107,54 @@ namespace DutilTests
         }
 
         [Fact]
+        void PathCanonicalizeForComparisonFallbackTest()
+        {
+            Path2FunctionForceFallback();
+
+            try
+            {
+                PathCanonicalizeForComparisonTestCore(FALSE);
+            }
+            finally
+            {
+                Path2FunctionAllowFallback();
+            }
+        }
+
+        [Fact]
         void PathCanonicalizeForComparisonTest()
         {
+            PathCanonicalizeForComparisonTestCore(TRUE);
+        }
+
+        void PathCanonicalizeForComparisonTestCore(BOOL fLongPathSupported)
+        {
             HRESULT hr = S_OK;
             LPWSTR sczCanonicalized = NULL;
 
             try
             {
                 hr = PathCanonicalizeForComparison(L"C:\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789", 0, &sczCanonicalized);
-                Assert::Equal<HRESULT>(HRESULT_FROM_WIN32(ERROR_FILENAME_EXCED_RANGE), hr);
+                if (!fLongPathSupported)
+                {
+                    Assert::Equal<HRESULT>(HRESULT_FROM_WIN32(ERROR_FILENAME_EXCED_RANGE), hr);
+                }
+                else
+                {
+                    NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                    NativeAssert::StringEqual(L"\\\\?\\C:\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789", sczCanonicalized);
+                }
 
                 hr = PathCanonicalizeForComparison(L"\\\\?\\C:\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789", 0, &sczCanonicalized);
-                Assert::Equal<HRESULT>(HRESULT_FROM_WIN32(ERROR_FILENAME_EXCED_RANGE), hr);
+                if (!fLongPathSupported)
+                {
+                    Assert::Equal<HRESULT>(HRESULT_FROM_WIN32(ERROR_FILENAME_EXCED_RANGE), hr);
+                }
+                else
+                {
+                    NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                    NativeAssert::StringEqual(L"\\\\?\\C:\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789", sczCanonicalized);
+                }
 
                 hr = PathCanonicalizeForComparison(L"\\\\server", PATH_CANONICALIZE_KEEP_UNC_ROOT, &sczCanonicalized);
                 NativeAssert::Succeeded(hr, "Failed to canonicalize path");
@@ -238,6 +279,52 @@ namespace DutilTests
         }
 
         [Fact]
+        void PathAllocCanonicalizePathTest()
+        {
+            HRESULT hr = S_OK;
+            LPWSTR sczCanonicalized = NULL;
+
+            try
+            {
+                hr = PathAllocCanonicalizePath(L"C:\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789", PATHCCH_ALLOW_LONG_PATHS, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"\\\\?\\C:\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789", sczCanonicalized);
+
+                hr = PathAllocCanonicalizePath(L"abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789", PATHCCH_ALLOW_LONG_PATHS, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789\\abcdefghijklomnopqrstuvwxyz0123456789", sczCanonicalized);
+
+                hr = PathAllocCanonicalizePath(L"\\\\server\\share\\..\\..\\otherdir\\unc.exe", PATHCCH_ALLOW_LONG_PATHS, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"\\\\otherdir\\unc.exe", sczCanonicalized); // This is surprising.
+
+                hr = PathAllocCanonicalizePath(L"C:\\dir\\subdir\\..\\..\\otherdir\\backslashes.exe", PATHCCH_ALLOW_LONG_PATHS, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"C:\\otherdir\\backslashes.exe", sczCanonicalized);
+
+                hr = PathAllocCanonicalizePath(L"C:/dir/subdir/../../otherdir/forwardslashes.exe", PATHCCH_ALLOW_LONG_PATHS, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"C:/dir/subdir/../../otherdir/forwardslashes.exe", sczCanonicalized);
+
+                hr = PathAllocCanonicalizePath(L"\\\\?\\C:\\test\\..\\validlongpath.exe", PATHCCH_ALLOW_LONG_PATHS, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"C:\\validlongpath.exe", sczCanonicalized);
+
+                hr = PathAllocCanonicalizePath(L"\\\\?\\test\\..\\invalidlongpath.exe", PATHCCH_ALLOW_LONG_PATHS, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"\\\\?\\invalidlongpath.exe", sczCanonicalized);
+
+                hr = PathAllocCanonicalizePath(L"C:\\.\\invalid:pathchars?.exe", PATHCCH_ALLOW_LONG_PATHS, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"C:\\invalid:pathchars?.exe", sczCanonicalized);
+            }
+            finally
+            {
+                ReleaseStr(sczCanonicalized);
+            }
+        }
+
+        [Fact]
         void PathConcatTest()
         {
             HRESULT hr = S_OK;
@@ -545,6 +632,25 @@ namespace DutilTests
         }
 
         [Fact]
+        void PathForCurrentProcessTest()
+        {
+            HRESULT hr = S_OK;
+            LPWSTR sczPath = NULL;
+
+            try
+            {
+                hr = PathForCurrentProcess(&sczPath, NULL);
+                NativeAssert::Succeeded(hr, "Failed to get current process path.");
+
+                WixAssert::StringEqual(System::Diagnostics::Process::GetCurrentProcess()->MainModule->FileName, gcnew String(sczPath), false);
+            }
+            finally
+            {
+                ReleaseStr(sczPath);
+            }
+        }
+
+        [Fact]
         void PathGetDirectoryTest()
         {
             HRESULT hr = S_OK;
@@ -828,6 +934,78 @@ namespace DutilTests
         }
 
         [Fact]
+        void PathGetTempPathTest()
+        {
+            HRESULT hr = S_OK;
+            LPCWSTR wzEnvName = L"TMP";
+            LPCWSTR wzEnvName2 = L"TEMP";
+            LPCWSTR wzLongTempPath = L"C:\\aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\\bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\\cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc\\";
+            LPWSTR sczTempPath = NULL;
+            WCHAR wzOriginalTemp[MAX_PATH + 1] = { };
+            WCHAR wzOriginalTemp2[MAX_PATH + 1] = { };
+            DWORD cch = 0;
+            DWORD cch2 = 0;
+            SIZE_T cchTemp = 0;
+            size_t cchTemp2 = 0;
+
+            try
+            {
+                cch = ::GetEnvironmentVariableW(wzEnvName, wzOriginalTemp, countof(wzOriginalTemp));
+                Assert::NotEqual<DWORD>(0, cch);
+
+                if (!::SetEnvironmentVariableW(wzEnvName, wzLongTempPath))
+                {
+                    Assert::Equal<DWORD>(0xFFFFFFFF, ::GetLastError());
+                }
+
+                cch2 = ::GetEnvironmentVariableW(wzEnvName2, wzOriginalTemp2, countof(wzOriginalTemp2));
+                Assert::NotEqual<DWORD>(0, cch2);
+
+                hr = PathGetTempPath(&sczTempPath, &cchTemp);
+                NativeAssert::Succeeded(hr, "Failed to get temp path.");
+
+                PathFixedBackslashTerminate(wzOriginalTemp2, countof(wzOriginalTemp2));
+
+                hr = ::StringCchLengthW(wzOriginalTemp2, countof(wzOriginalTemp2), &cchTemp2);
+                NativeAssert::Succeeded(hr, "Failed to get temp path length.");
+
+                NativeAssert::StringEqual(wzOriginalTemp2, sczTempPath);
+                Assert::Equal<SIZE_T>(cchTemp2, cchTemp);
+            }
+            finally
+            {
+                if (cch)
+                {
+                    ::SetEnvironmentVariableW(wzEnvName, wzOriginalTemp);
+                }
+
+                ReleaseStr(sczTempPath);
+            }
+        }
+
+        [Fact]
+        void PathGetVolumePathNameTest()
+        {
+            HRESULT hr = S_OK;
+            LPWSTR sczVolumePathName = NULL;
+
+            try
+            {
+                hr = StrAlloc(&sczVolumePathName, 1);
+                NativeAssert::Succeeded(hr, "Failed to alloc volume path name.");
+
+                hr = PathGetVolumePathName(L"C:\\Windows", &sczVolumePathName);
+                NativeAssert::Succeeded(hr, "PathGetVolumePathName failed.");
+
+                NativeAssert::StringEqual(L"C:\\", sczVolumePathName);
+            }
+            finally
+            {
+                ReleaseStr(sczVolumePathName);
+            }
+        }
+
+        [Fact]
         void PathNormalizeSlashesFixedTest()
         {
             HRESULT hr = S_OK;
diff --git a/src/test/burn/Directory.wixproj.targets b/src/test/burn/Directory.wixproj.targets
index 17a46e2a..4037e865 100644
--- a/src/test/burn/Directory.wixproj.targets
+++ b/src/test/burn/Directory.wixproj.targets
@@ -7,6 +7,7 @@
     <WebServerBaseUrl Condition=" '$(WebServerBaseUrl)' == '' ">http://localhost:9999/e2e/</WebServerBaseUrl>
     <DefineConstants>TestGroupName=$(TestGroupName);PackageName=$(PackageName);BundleName=$(BundleName);WebServerBaseUrl=$(WebServerBaseUrl);$(DefineConstants)</DefineConstants>
     <DefineConstants Condition=" '$(BA)' != '' ">BA=$(BA);$(DefineConstants)</DefineConstants>
+    <DefineConstants Condition=" '$(BundleLogDirectory)' != '' ">BundleLogDirectory=$(BundleLogDirectory);$(DefineConstants)</DefineConstants>
     <DefineConstants Condition=" '$(CabPrefix)' != '' ">CabPrefix=$(CabPrefix);$(DefineConstants)</DefineConstants>
     <DefineConstants Condition=" '$(IncludeSoftwareTag)' == 'true' ">SoftwareTag=1;$(DefineConstants)</DefineConstants>
     <DefineConstants Condition=" '$(ProductCode)' != '' ">ProductCode=$(ProductCode);$(DefineConstants)</DefineConstants>
diff --git a/src/test/burn/TestData/LongPathTests/NonCompressedBundle/NonCompressedBundle.wixproj b/src/test/burn/TestData/LongPathTests/NonCompressedBundle/NonCompressedBundle.wixproj
new file mode 100644
index 00000000..3686200c
--- /dev/null
+++ b/src/test/burn/TestData/LongPathTests/NonCompressedBundle/NonCompressedBundle.wixproj
@@ -0,0 +1,19 @@
+<!-- Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information. -->
+<Project Sdk="WixToolset.Sdk">
+  <PropertyGroup>
+    <OutputType>Bundle</OutputType>
+    <UpgradeCode>{EFCF768F-1B06-4B68-9DE0-9244F8212D31}</UpgradeCode>
+    <BundleLogDirectory>[LocalAppDataFolder]Temp</BundleLogDirectory>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="..\..\Templates\Bundle.wxs" Link="Bundle.wxs" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\PackageA\PackageA.wixproj" />
+    <ProjectReference Include="..\..\TestBA\TestBAWixlib\testbawixlib.wixproj" />
+  </ItemGroup>
+  <ItemGroup>
+    <PackageReference Include="WixToolset.Bal.wixext" />
+    <PackageReference Include="WixToolset.NetFx.wixext" />
+  </ItemGroup>
+</Project>
\ No newline at end of file
diff --git a/src/test/burn/TestData/LongPathTests/NonCompressedBundle/NonCompressedBundle.wxs b/src/test/burn/TestData/LongPathTests/NonCompressedBundle/NonCompressedBundle.wxs
new file mode 100644
index 00000000..e3872eb1
--- /dev/null
+++ b/src/test/burn/TestData/LongPathTests/NonCompressedBundle/NonCompressedBundle.wxs
@@ -0,0 +1,10 @@
+<!-- Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information. -->
+
+
+<Wix xmlns="http://wixtoolset.org/schemas/v4/wxs">
+  <Fragment>
+    <PackageGroup Id="BundlePackages">
+      <MsiPackage Compressed="no" Id="PackageA" SourceFile="$(var.PackageA.TargetPath)" />
+    </PackageGroup>
+  </Fragment>
+</Wix>
diff --git a/src/test/burn/TestData/LongPathTests/PackageA/PackageA.wixproj b/src/test/burn/TestData/LongPathTests/PackageA/PackageA.wixproj
new file mode 100644
index 00000000..798452e7
--- /dev/null
+++ b/src/test/burn/TestData/LongPathTests/PackageA/PackageA.wixproj
@@ -0,0 +1,10 @@
+<!-- Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information. -->
+<Project Sdk="WixToolset.Sdk">
+  <PropertyGroup>
+    <CabPrefix>a</CabPrefix>
+    <UpgradeCode>{4DC05A2A-382D-4E7D-B6DA-163908396373}</UpgradeCode>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="..\..\Templates\Package.wxs" Link="Package.wxs" />
+  </ItemGroup>
+</Project>
\ No newline at end of file
diff --git a/src/test/burn/TestData/Templates/Bundle.wxs b/src/test/burn/TestData/Templates/Bundle.wxs
index b211d9c3..612e67f5 100644
--- a/src/test/burn/TestData/Templates/Bundle.wxs
+++ b/src/test/burn/TestData/Templates/Bundle.wxs
@@ -3,10 +3,13 @@
 <?ifndef Version?>
 <?define Version = 1.0.0.0?>
 <?endif?>
+<?ifndef BundleLogDirectory?>
+<?define BundleLogDirectory = .?>
+<?endif?>
 
 <Wix xmlns="http://wixtoolset.org/schemas/v4/wxs" xmlns:bal="http://wixtoolset.org/schemas/v4/wxs/bal">
   <Bundle Name="~$(var.TestGroupName) - $(var.BundleName)" Version="$(var.Version)" UpgradeCode="$(var.UpgradeCode)" Compressed="yes">
-    <Log Prefix="~$(var.TestGroupName)_$(var.BundleName)" />
+    <Log Prefix="$(var.BundleLogDirectory)\~$(var.TestGroupName)_$(var.BundleName)" />
 
     <Variable Name="TestGroupName" Value="$(var.TestGroupName)" />
 
diff --git a/src/test/burn/TestExe/Task.cs b/src/test/burn/TestExe/Task.cs
index 59f774fb..0d283c6c 100644
--- a/src/test/burn/TestExe/Task.cs
+++ b/src/test/burn/TestExe/Task.cs
@@ -2,8 +2,10 @@
 
 using System;
 using System.Collections.Generic;
+using System.ComponentModel;
 using System.Diagnostics;
 using System.IO;
+using System.Runtime.InteropServices;
 using Microsoft.Win32;
 
 namespace TestExe
@@ -151,6 +153,67 @@ namespace TestExe
         }
     }
 
+    public class DeleteManifestsTask : Task
+    {
+        public DeleteManifestsTask(string Data) : base(Data) { }
+
+        public override void RunTask()
+        {
+            string filePath = System.Environment.ExpandEnvironmentVariables(this.data);
+            IntPtr type = new IntPtr(24); //RT_MANIFEST
+            IntPtr name = new IntPtr(1); //CREATEPROCESS_MANIFEST_RESOURCE_ID
+            DeleteResource(filePath, type, name, 1033);
+        }
+
+        private static void DeleteResource(string filePath, IntPtr type, IntPtr name, ushort language, bool throwOnError = false)
+        {
+            bool discard = true;
+            IntPtr handle = BeginUpdateResourceW(filePath, false);
+            try
+            {
+                if (handle == IntPtr.Zero)
+                {
+                    throw new Win32Exception();
+                }
+
+                if (!UpdateResourceW(handle, type, name, language, IntPtr.Zero, 0))
+                {
+                    throw new Win32Exception();
+                }
+
+                discard = false;
+            }
+            catch
+            {
+                if (throwOnError)
+                {
+                    throw;
+                }
+            }
+            finally
+            {
+                if (handle != IntPtr.Zero)
+                {
+                    if (!EndUpdateResourceW(handle, discard) && throwOnError)
+                    {
+                        throw new Win32Exception();
+                    }
+                }
+            }
+        }
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode, ExactSpelling = true, SetLastError = true)]
+        private extern static IntPtr BeginUpdateResourceW(string fileName, [MarshalAs(UnmanagedType.Bool)] bool deleteExistingResources);
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode, ExactSpelling = true, SetLastError = true)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private extern static bool UpdateResourceW(IntPtr hUpdate, IntPtr type, IntPtr name, ushort language, IntPtr pData, uint cb);
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode, ExactSpelling = true, SetLastError = true)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private extern static bool EndUpdateResourceW(IntPtr hUpdate, [MarshalAs(UnmanagedType.Bool)] bool discard);
+    }
+
     public class TaskParser
     {
 
@@ -197,6 +260,10 @@ namespace TestExe
                                 t = new FileExistsTask(args[i + 1]);
                                 tasks.Add(t);
                                 break;
+                            case "/dm":
+                                t = new DeleteManifestsTask(args[i + 1]);
+                                tasks.Add(t);
+                                break;
 #if NET35
                             case "/pinfo":
                                 t = new ProcessInfoTask(args[i + 1]);
diff --git a/src/test/burn/WixTestTools/BundleInstaller.cs b/src/test/burn/WixTestTools/BundleInstaller.cs
index 5551d3c0..0f2cfa8f 100644
--- a/src/test/burn/WixTestTools/BundleInstaller.cs
+++ b/src/test/burn/WixTestTools/BundleInstaller.cs
@@ -28,6 +28,8 @@ namespace WixTestTools
 
         public int? AlternateExitCode { get; set; }
 
+        public string LogDirectory { get; set; }
+
         public int? LastExitCode { get; set; }
 
         /// <summary>
@@ -194,7 +196,7 @@ namespace WixTestTools
             sb.Append(" -quiet");
             
             // Generate the log file name.
-            string logFile = Path.Combine(Path.GetTempPath(), String.Format("{0}_{1}_{2:yyyyMMddhhmmss}_{4}_{3}.log", this.TestGroupName, this.TestName, DateTime.UtcNow, Path.GetFileNameWithoutExtension(this.Bundle), mode));
+            string logFile = Path.Combine(this.LogDirectory ?? Path.GetTempPath(), String.Format("{0}_{1}_{2:yyyyMMddhhmmss}_{4}_{3}.log", this.TestGroupName, this.TestName, DateTime.UtcNow, Path.GetFileNameWithoutExtension(this.Bundle), mode));
             sb.AppendFormat(" -log \"{0}\"", logFile);
 
             // Set operation.
diff --git a/src/test/burn/WixTestTools/MSIExec.cs b/src/test/burn/WixTestTools/MSIExec.cs
index a10a48d6..5f57da7b 100644
--- a/src/test/burn/WixTestTools/MSIExec.cs
+++ b/src/test/burn/WixTestTools/MSIExec.cs
@@ -110,7 +110,7 @@ namespace WixTestTools
             this.NoRestart = true;
             this.ForceRestart = false;
             this.PromptRestart = false;
-            this.LogFile = string.Empty;
+            this.LogFile = String.Empty;
             this.LoggingOptions = MSIExecLoggingOptions.VOICEWARMUP;
             this.OtherArguments = String.Empty;
         }
@@ -230,14 +230,14 @@ namespace WixTestTools
             }
 
             // logfile and logging options
-            if (0 != loggingOptionsString.Length || !string.IsNullOrEmpty(this.LogFile))
+            if (0 != loggingOptionsString.Length || !String.IsNullOrEmpty(this.LogFile))
             {
                 arguments.Append(" /l");
                 if (0 != loggingOptionsString.Length)
                 {
                     arguments.AppendFormat("{0} ", loggingOptionsString);
                 }
-                if (!string.IsNullOrEmpty(this.LogFile))
+                if (!String.IsNullOrEmpty(this.LogFile))
                 {
                     arguments.AppendFormat(" \"{0}\" ", this.LogFile);
                 }
@@ -268,7 +268,7 @@ namespace WixTestTools
             };
 
             // product
-            if (!string.IsNullOrEmpty(this.Product))
+            if (!String.IsNullOrEmpty(this.Product))
             {
                 arguments.AppendFormat(" \"{0}\" ", this.Product);
             }
@@ -311,6 +311,12 @@ namespace WixTestTools
             ERROR_CALL_NOT_IMPLEMENTED = 120,
 
             /// <summary>
+            /// ERROR_FILENAME_EXCED_RANGE              206
+            /// The filename or extension is too long.
+            /// </summary>
+            ERROR_FILENAME_EXCED_RANGE = 206,
+
+            /// <summary>
             /// ERROR_APPHELP_BLOCK                     1259 
             /// If Windows Installer determines a product may be incompatible with the current operating system, 
             /// it displays a dialog box informing the user and asking whether to try to install anyway. 
diff --git a/src/test/burn/WixTestTools/TestTool.cs b/src/test/burn/WixTestTools/TestTool.cs
index eb77c75b..79e7004c 100644
--- a/src/test/burn/WixTestTools/TestTool.cs
+++ b/src/test/burn/WixTestTools/TestTool.cs
@@ -229,7 +229,7 @@ namespace WixTestTools
             returnValue.AppendLine("Tool run result:");
             returnValue.AppendLine("----------------");
             returnValue.AppendLine("Command:");
-            returnValue.AppendLine($"\"{result.StartInfo.FileName}\" {result.StartInfo.Arguments}");
+            returnValue.AppendLine($"\"{result.FileName}\" {result.Arguments}");
             returnValue.AppendLine();
             returnValue.AppendLine("Standard Output:");
             foreach (var line in result.StandardOutput ?? new string[0])
diff --git a/src/test/burn/WixToolsetTest.BurnE2E/LongPathTests.cs b/src/test/burn/WixToolsetTest.BurnE2E/LongPathTests.cs
new file mode 100644
index 00000000..ba793d7a
--- /dev/null
+++ b/src/test/burn/WixToolsetTest.BurnE2E/LongPathTests.cs
@@ -0,0 +1,298 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information.
+
+namespace WixToolsetTest.BurnE2E
+{
+    using System;
+    using System.ComponentModel;
+    using System.IO;
+    using System.Runtime.InteropServices;
+    using Microsoft.Win32;
+    using WixBuildTools.TestSupport;
+    using WixTestTools;
+    using WixToolset.Mba.Core;
+    using Xunit;
+    using Xunit.Abstractions;
+
+    public class LongPathTests : BurnE2ETests
+    {
+        public LongPathTests(ITestOutputHelper testOutputHelper) : base(testOutputHelper) { }
+
+        [RuntimeFact]
+        public void CanInstallAndUninstallSimpleBundle_x86_wixstdba()
+        {
+            this.CanInstallAndUninstallSimpleBundle("PackageA", "BundleA");
+        }
+
+        [RuntimeFact]
+        public void CanInstallAndUninstallSimpleBundle_x86_testba()
+        {
+            this.CanInstallAndUninstallSimpleBundle("PackageA", "BundleB");
+        }
+
+        [RuntimeFact]
+        public void CanInstallAndUninstallSimpleBundle_x86_dnctestba()
+        {
+            this.CanInstallAndUninstallSimpleBundle("PackageA", "BundleC");
+        }
+
+        [RuntimeFact]
+        public void CanInstallAndUninstallSimpleBundle_x86_wixba()
+        {
+            this.CanInstallAndUninstallSimpleBundle("PackageA", "BundleD");
+        }
+
+        [RuntimeFact]
+        public void CanInstallAndUninstallSimpleBundle_x64_wixstdba()
+        {
+            this.CanInstallAndUninstallSimpleBundle("PackageA_x64", "BundleA_x64");
+        }
+
+        [RuntimeFact]
+        public void CanInstallAndUninstallSimplePerUserBundle_x64_wixstdba()
+        {
+            this.CanInstallAndUninstallSimpleBundle("PackageApu_x64", "BundleApu_x64", "PackagePerUser.wxs", unchecked((int)0xc0000005));
+        }
+
+        [RuntimeFact]
+        public void CanInstallAndUninstallSimpleBundle_x64_testba()
+        {
+            this.CanInstallAndUninstallSimpleBundle("PackageA_x64", "BundleB_x64");
+        }
+
+        [RuntimeFact]
+        public void CanInstallAndUninstallSimpleBundle_x64_dnctestba()
+        {
+            this.CanInstallAndUninstallSimpleBundle("PackageA_x64", "BundleC_x64");
+        }
+
+        [RuntimeFact]
+        public void CanInstallAndUninstallSimpleBundle_x64_dncwixba()
+        {
+            this.CanInstallAndUninstallSimpleBundle("PackageA_x64", "BundleD_x64");
+        }
+
+        private void CanInstallAndUninstallSimpleBundle(string packageName, string bundleName, string fileName = "Package.wxs", int? alternateExitCode = null)
+        {
+            var package = this.CreatePackageInstaller(Path.Combine("..", "BasicFunctionalityTests", packageName));
+
+            var bundle = this.CreateBundleInstaller(Path.Combine("..", "BasicFunctionalityTests", bundleName));
+            bundle.AlternateExitCode = alternateExitCode;
+
+            using var dfs = new DisposableFileSystem();
+            var baseFolder = GetLongPath(dfs.GetFolder());
+
+            var packageSourceCodeInstalled = package.GetInstalledFilePath(fileName);
+
+            // Source file should *not* be installed
+            Assert.False(File.Exists(packageSourceCodeInstalled), $"{packageName} payload should not be there on test start: {packageSourceCodeInstalled}");
+
+            var bundleFileInfo = new FileInfo(bundle.Bundle);
+            var bundleCopiedPath = Path.Combine(baseFolder, bundleFileInfo.Name);
+            bundleFileInfo.CopyTo(bundleCopiedPath);
+
+            bundle.Install(bundleCopiedPath);
+            bundle.VerifyRegisteredAndInPackageCache();
+
+            // Source file should be installed
+            Assert.True(File.Exists(packageSourceCodeInstalled), $"Should have found {packageName} payload installed at: {packageSourceCodeInstalled}");
+
+            if (alternateExitCode == bundle.LastExitCode)
+            {
+                WixAssert.Skip($"Install exited with {bundle.LastExitCode}");
+            }
+
+            bundle.Uninstall(bundleCopiedPath);
+
+            // Source file should *not* be installed
+            Assert.False(File.Exists(packageSourceCodeInstalled), $"{packageName} payload should have been removed by uninstall from: {packageSourceCodeInstalled}");
+
+            bundle.VerifyUnregisteredAndRemovedFromPackageCache();
+
+            if (alternateExitCode == bundle.LastExitCode)
+            {
+                WixAssert.Skip($"Uninstall exited with {bundle.LastExitCode}");
+            }
+        }
+
+        [RuntimeFact]
+        public void CanLayoutNonCompressedBundleToLongPath()
+        {
+            var nonCompressedBundle = this.CreateBundleInstaller("NonCompressedBundle");
+            var testBAController = this.CreateTestBAController();
+
+            testBAController.SetPackageRequestedState("NetFx48Web", RequestState.None);
+
+            using var dfs = new DisposableFileSystem();
+            var layoutDirectory = GetLongPath(dfs.GetFolder());
+
+            nonCompressedBundle.Layout(layoutDirectory);
+            nonCompressedBundle.VerifyUnregisteredAndRemovedFromPackageCache();
+
+            Assert.True(File.Exists(Path.Combine(layoutDirectory, "NonCompressedBundle.exe")));
+            Assert.True(File.Exists(Path.Combine(layoutDirectory, "PackageA.msi")));
+            Assert.True(File.Exists(Path.Combine(layoutDirectory, "1a.cab")));
+            Assert.False(File.Exists(Path.Combine(layoutDirectory, @"redist\ndp48-web.exe")));
+        }
+
+        [RuntimeFact]
+        public void CanInstallNonCompressedBundleWithLongTempPath()
+        {
+            this.InstallNonCompressedBundle(longTemp: true, useOriginalTempForLog: true);
+        }
+
+        [RuntimeFact]
+        public void CannotInstallNonCompressedBundleWithLongPackageCachePath()
+        {
+            var installLogPath = this.InstallNonCompressedBundle((int)MSIExec.MSIExecReturnCode.ERROR_INSTALL_FAILURE, longPackageCache: true);
+            Assert.True(LogVerifier.MessageInLogFile(installLogPath, @"Error 0x80070643: Failed to install MSI package"));
+        }
+
+        [RuntimeFact]
+        public void CannotInstallNonCompressedBundleWithLongWorkingPath()
+        {
+            var installLogPath = this.InstallNonCompressedBundle((int)MSIExec.MSIExecReturnCode.ERROR_FILENAME_EXCED_RANGE | unchecked((int)0x80070000), longWorkingPath: true);
+            Assert.True(LogVerifier.MessageInLogFile(installLogPath, @"Error 0x800700ce: Failed to load BA DLL"));
+        }
+
+        public string InstallNonCompressedBundle(int expectedExitCode = 0, bool longTemp = false, bool useOriginalTempForLog = false, bool longWorkingPath = false, bool longPackageCache = false, int? alternateExitCode = null)
+        {
+            var deletePolicyKey = false;
+            string originalEngineWorkingDirectoryValue = null;
+            string originalPackageCacheValue = null;
+            var originalTemp = Environment.GetEnvironmentVariable("TMP");
+            var packageA = this.CreatePackageInstaller("PackageA");
+            var nonCompressedBundle = this.CreateBundleInstaller("NonCompressedBundle");
+            var policyPath = nonCompressedBundle.GetFullBurnPolicyRegistryPath();
+            string installLogPath = null;
+
+            try
+            {
+                using var dfs = new DisposableFileSystem();
+                var originalBaseFolder = dfs.GetFolder();
+                var baseFolder = GetLongPath(originalBaseFolder);
+                var sourceFolder = Path.Combine(baseFolder, "source");
+                var workingFolder = Path.Combine(baseFolder, "working");
+                var tempFolder = Path.Combine(originalBaseFolder, new string('d', 260 - originalBaseFolder.Length - 2));
+                var packageCacheFolder = Path.Combine(baseFolder, "package cache");
+
+                var copyResult = TestDataFolderFileSystem.RobocopyFolder(this.TestContext.TestDataFolder, sourceFolder);
+                Assert.True(copyResult.ExitCode >= 0 && copyResult.ExitCode < 8, $"Exit code: {copyResult.ExitCode}\r\nOutput: {String.Join("\r\n", copyResult.StandardOutput)}\r\nError: {String.Join("\r\n", copyResult.StandardError)}");
+
+                var bundleFileInfo = new FileInfo(nonCompressedBundle.Bundle);
+                var bundleCopiedPath = Path.Combine(sourceFolder, bundleFileInfo.Name);
+
+                var policyKey = Registry.LocalMachine.OpenSubKey(policyPath, writable: true);
+                if (policyKey == null)
+                {
+                    policyKey = Registry.LocalMachine.CreateSubKey(policyPath, writable: true);
+                    deletePolicyKey = true;
+                }
+
+                using (policyKey)
+                {
+                    originalEngineWorkingDirectoryValue = policyKey.GetValue("EngineWorkingDirectory") as string;
+                    originalPackageCacheValue = policyKey.GetValue("PackageCache") as string;
+
+                    if (longWorkingPath)
+                    {
+                        policyKey.SetValue("EngineWorkingDirectory", workingFolder);
+                    }
+
+                    if (longPackageCache)
+                    {
+                        policyKey.SetValue("PackageCache", packageCacheFolder);
+                    }
+                }
+
+                if (longTemp)
+                {
+                    Environment.SetEnvironmentVariable("TMP", tempFolder);
+
+                    if (useOriginalTempForLog)
+                    {
+                        nonCompressedBundle.LogDirectory = originalTemp;
+                    }
+                }
+
+                try
+                {
+                    nonCompressedBundle.AlternateExitCode = alternateExitCode;
+                    installLogPath = nonCompressedBundle.Install(bundleCopiedPath, expectedExitCode);
+
+                    if (alternateExitCode == nonCompressedBundle.LastExitCode)
+                    {
+                        WixAssert.Skip($"Install exited with {nonCompressedBundle.LastExitCode}");
+                    }
+                }
+                finally
+                {
+                    TestDataFolderFileSystem.RobocopyFolder(tempFolder, originalTemp);
+                }
+
+                installLogPath = Path.Combine(originalTemp, Path.GetFileName(installLogPath));
+
+                if (expectedExitCode == 0)
+                {
+                    var registration = nonCompressedBundle.VerifyRegisteredAndInPackageCache();
+                    packageA.VerifyInstalled(true);
+
+                    nonCompressedBundle.Uninstall(registration.CachePath);
+
+                    if (alternateExitCode == nonCompressedBundle.LastExitCode)
+                    {
+                        WixAssert.Skip($"Uninstall exited with {nonCompressedBundle.LastExitCode}");
+                    }
+                }
+
+                nonCompressedBundle.VerifyUnregisteredAndRemovedFromPackageCache();
+                packageA.VerifyInstalled(false);
+
+                return installLogPath;
+            }
+            finally
+            {
+                Environment.SetEnvironmentVariable("TMP", originalTemp);
+
+                if (deletePolicyKey)
+                {
+                    Registry.LocalMachine.DeleteSubKeyTree(policyPath);
+                }
+                else
+                {
+                    using (var policyKey = Registry.LocalMachine.OpenSubKey(policyPath, writable: true))
+                    {
+                        policyKey?.SetValue("EngineWorkingDirectory", originalEngineWorkingDirectoryValue);
+                        policyKey?.SetValue("PackageCache", originalPackageCacheValue);
+                    }
+                }
+            }
+        }
+
+        private static string GetLongPath(string baseFolder)
+        {
+            Directory.CreateDirectory(baseFolder);
+
+            // Try to create a directory that is longer than MAX_PATH but without the \\?\ prefix to detect OS support for long paths.
+            // Need to PInvoke CreateDirectoryW directly because .NET methods will append the \\?\ prefix.
+            foreach (var c in new char[] { 'a', 'b', 'c' })
+            {
+                baseFolder = Path.Combine(baseFolder, new string(c, 100));
+                if (!CreateDirectoryW(baseFolder, IntPtr.Zero))
+                {
+                    int lastError = Marshal.GetLastWin32Error();
+                    if (lastError == 206)
+                    {
+                        WixAssert.Skip($"MAX_PATH is being enforced ({baseFolder})");
+                    }
+                    throw new Win32Exception(lastError);
+                }
+            }
+
+            return baseFolder;
+        }
+
+        [DllImport("kernel32.dll", CharSet = CharSet.Unicode, ExactSpelling = true, SetLastError = true)]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private extern static bool CreateDirectoryW(string lpPathName, IntPtr lpSecurityAttributes);
+    }
+}
diff --git a/src/test/burn/WixToolsetTest.BurnE2E/testhost.longpathaware.manifest b/src/test/burn/WixToolsetTest.BurnE2E/testhost.longpathaware.manifest
new file mode 100644
index 00000000..a56ab91a
--- /dev/null
+++ b/src/test/burn/WixToolsetTest.BurnE2E/testhost.longpathaware.manifest
@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<!-- Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information. -->
+
+
+<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
+ <application xmlns="urn:schemas-microsoft-com:asm.v3">
+  <windowsSettings xmlns:ws2="http://schemas.microsoft.com/SMI/2016/WindowsSettings">
+   <ws2:longPathAware>true</ws2:longPathAware>
+  </windowsSettings>
+ </application>
+</assembly>
diff --git a/src/test/burn/test_burn.cmd b/src/test/burn/test_burn.cmd
index 83401614..80467f39 100644
--- a/src/test/burn/test_burn.cmd
+++ b/src/test/burn/test_burn.cmd
@@ -9,11 +9,16 @@
 @if /i "%1"=="test" set RuntimeTestsEnabled=true
 @if not "%1"=="" shift & goto parse_args
 
+@set _B=%~dp0..\..\..\build\IntegrationBurn\%_C%
+
 @echo Burn integration tests %_C%
 
 msbuild -t:Build -Restore -p:Configuration=%_C% -warnaserror -bl:%_L%\test_burn_build.binlog || exit /b
 msbuild -t:Build -Restore TestData\TestData.proj -p:Configuration=%_C% -m -bl:%_L%\test_burn_data_build.binlog || exit /b
 
+"%_B%\net35\win-x86\testexe.exe" /dm "%_B%\netcoreapp3.1\testhost.exe"
+mt.exe -manifest "WixToolsetTest.BurnE2E\testhost.longpathaware.manifest" -updateresource:"%_B%\netcoreapp3.1\testhost.exe"
+
 @if not "%RuntimeTestsEnabled%"=="true" goto :LExit
 
 dotnet test -c %_C% --no-build WixToolsetTest.BurnE2E -l "trx;LogFileName=%_L%\TestResults\WixToolsetTest.BurnE2E.trx" || exit /b
diff --git a/src/wix/WixToolset.Core.Burn/Bundles/CreateBundleExeCommand.cs b/src/wix/WixToolset.Core.Burn/Bundles/CreateBundleExeCommand.cs
index 672bb235..67a6cb4a 100644
--- a/src/wix/WixToolset.Core.Burn/Bundles/CreateBundleExeCommand.cs
+++ b/src/wix/WixToolset.Core.Burn/Bundles/CreateBundleExeCommand.cs
@@ -231,6 +231,10 @@ namespace WixToolset.Core.Burn.Bundles
                         writer.WriteEndElement();
                     }
 
+                    writer.WriteStartElement("longPathAware", ws2016Namespace);
+                    writer.WriteString("true");
+                    writer.WriteEndElement();
+
                     writer.WriteEndElement(); // </windowSettings>
                     writer.WriteEndElement(); // </application>
                 }
diff --git a/src/wix/test/WixToolsetTest.CoreIntegration/BundleFixture.cs b/src/wix/test/WixToolsetTest.CoreIntegration/BundleFixture.cs
index bc7fe7a4..a281ad0f 100644
--- a/src/wix/test/WixToolsetTest.CoreIntegration/BundleFixture.cs
+++ b/src/wix/test/WixToolsetTest.CoreIntegration/BundleFixture.cs
@@ -169,7 +169,10 @@ namespace WixToolsetTest.CoreIntegration
                     "<dependency><dependentAssembly><assemblyIdentity name=\"Microsoft.Windows.Common-Controls\" version=\"6.0.0.0\" processorArchitecture=\"x86\" publicKeyToken=\"6595b64144ccf1df\" language=\"*\" type=\"win32\" /></dependentAssembly></dependency>" +
                     "<compatibility xmlns=\"urn:schemas-microsoft-com:compatibility.v1\"><application><supportedOS Id=\"{e2011457-1546-43c5-a5fe-008deee3d3f0}\" /><supportedOS Id=\"{35138b9a-5d96-4fbd-8e2d-a2440225f93a}\" /><supportedOS Id=\"{4a2f28e3-53b9-4441-ba9c-d69d4a4a6e38}\" /><supportedOS Id=\"{1f676c76-80e1-4239-95bb-83d0f6d0da78}\" /><supportedOS Id=\"{8e0f7a12-bfb3-4fe8-b9a5-48fd50a15a9a}\" /></application></compatibility>" +
                     "<trustInfo xmlns=\"urn:schemas-microsoft-com:asm.v3\"><security><requestedPrivileges><requestedExecutionLevel level=\"asInvoker\" uiAccess=\"false\" /></requestedPrivileges></security></trustInfo>" +
-                    "<application xmlns=\"urn:schemas-microsoft-com:asm.v3\"><windowsSettings><dpiAware xmlns=\"http://schemas.microsoft.com/SMI/2005/WindowsSettings\">true/pm</dpiAware><dpiAwareness xmlns=\"http://schemas.microsoft.com/SMI/2016/WindowsSettings\">PerMonitorV2, PerMonitor</dpiAwareness></windowsSettings></application>" +
+                    "<application xmlns=\"urn:schemas-microsoft-com:asm.v3\"><windowsSettings>" +
+                    "<dpiAware xmlns=\"http://schemas.microsoft.com/SMI/2005/WindowsSettings\">true/pm</dpiAware><dpiAwareness xmlns=\"http://schemas.microsoft.com/SMI/2016/WindowsSettings\">PerMonitorV2, PerMonitor</dpiAwareness>" +
+                    "<longPathAware xmlns=\"http://schemas.microsoft.com/SMI/2016/WindowsSettings\">true</longPathAware>" +
+                    "</windowsSettings></application>" +
                     "</assembly>", actualManifestData);
             }
         }
@@ -215,7 +218,10 @@ namespace WixToolsetTest.CoreIntegration
                     "<dependency><dependentAssembly><assemblyIdentity name=\"Microsoft.Windows.Common-Controls\" version=\"6.0.0.0\" processorArchitecture=\"amd64\" publicKeyToken=\"6595b64144ccf1df\" language=\"*\" type=\"win32\" /></dependentAssembly></dependency>" +
                     "<compatibility xmlns=\"urn:schemas-microsoft-com:compatibility.v1\"><application><supportedOS Id=\"{e2011457-1546-43c5-a5fe-008deee3d3f0}\" /><supportedOS Id=\"{35138b9a-5d96-4fbd-8e2d-a2440225f93a}\" /><supportedOS Id=\"{4a2f28e3-53b9-4441-ba9c-d69d4a4a6e38}\" /><supportedOS Id=\"{1f676c76-80e1-4239-95bb-83d0f6d0da78}\" /><supportedOS Id=\"{8e0f7a12-bfb3-4fe8-b9a5-48fd50a15a9a}\" /></application></compatibility>" +
                     "<trustInfo xmlns=\"urn:schemas-microsoft-com:asm.v3\"><security><requestedPrivileges><requestedExecutionLevel level=\"asInvoker\" uiAccess=\"false\" /></requestedPrivileges></security></trustInfo>" +
-                    "<application xmlns=\"urn:schemas-microsoft-com:asm.v3\"><windowsSettings><dpiAware xmlns=\"http://schemas.microsoft.com/SMI/2005/WindowsSettings\">true/pm</dpiAware><dpiAwareness xmlns=\"http://schemas.microsoft.com/SMI/2016/WindowsSettings\">PerMonitorV2, PerMonitor</dpiAwareness></windowsSettings></application>" +
+                    "<application xmlns=\"urn:schemas-microsoft-com:asm.v3\"><windowsSettings>" +
+                    "<dpiAware xmlns=\"http://schemas.microsoft.com/SMI/2005/WindowsSettings\">true/pm</dpiAware><dpiAwareness xmlns=\"http://schemas.microsoft.com/SMI/2016/WindowsSettings\">PerMonitorV2, PerMonitor</dpiAwareness>" +
+                    "<longPathAware xmlns=\"http://schemas.microsoft.com/SMI/2016/WindowsSettings\">true</longPathAware>" +
+                    "</windowsSettings></application>" +
                     "</assembly>", actualManifestData);
 
                 var extractResult = BundleExtractor.ExtractAllContainers(null, exePath, baFolderPath, attachedFolderPath, extractFolderPath);