8 files changed, 822 insertions, 116 deletions

diff --git a/src/burn/engine/variable.cpp b/src/burn/engine/variable.cpp
index 718751e5..c96e9d95 100644
--- a/src/burn/engine/variable.cpp
+++ b/src/burn/engine/variable.cpp
@@ -1969,7 +1969,7 @@ static HRESULT InitializeVariableSystemFolder(
 {
     HRESULT hr = S_OK;
     BOOL f64 = (BOOL)dwpData;
-    WCHAR wzSystemFolder[MAX_PATH] = { };
+    WCHAR wzSystemFolder[MAX_PATH + 2] = { };
 
 #if !defined(_WIN64)
     BOOL fIsWow64 = FALSE;
diff --git a/src/libs/dutil/WixToolset.DUtil/inc/pathutil.h b/src/libs/dutil/WixToolset.DUtil/inc/pathutil.h
index 602b4a80..fc6bb3bb 100644
--- a/src/libs/dutil/WixToolset.DUtil/inc/pathutil.h
+++ b/src/libs/dutil/WixToolset.DUtil/inc/pathutil.h
@@ -6,7 +6,17 @@
 extern "C" {
 #endif
 
-typedef enum PATH_EXPAND
+typedef enum _PATH_CANONICALIZE
+{
+    // Always prefix fully qualified paths with the long path prefix (\\?\).
+    PATH_CANONICALIZE_APPEND_LONG_PATH_PREFIX = 0x0001,
+    // Always terminate the path with \.
+    PATH_CANONICALIZE_BACKSLASH_TERMINATE = 0x0002,
+    // Don't collapse . or .. in the \\server\share portion of a UNC path.
+    PATH_CANONICALIZE_KEEP_UNC_ROOT = 0x0004,
+} PATH_CANONICALIZE;
+
+typedef enum _PATH_EXPAND
 {
     PATH_EXPAND_ENVIRONMENT = 0x0001,
     PATH_EXPAND_FULLPATH    = 0x0002,
@@ -29,7 +39,9 @@ DAPI_(LPCWSTR) PathExtension(
     );
 
 /*******************************************************************
- PathGetDirectory - extracts the directory from a path.
+ PathGetDirectory - extracts the directory from a path including the directory separator.
+                    This means calling the function again with the previous result returns the same result.
+                    Returns S_FALSE if the path only contains a file name.
 ********************************************************************/
 DAPI_(HRESULT) PathGetDirectory(
     __in_z LPCWSTR wzPath,
@@ -38,6 +50,7 @@ DAPI_(HRESULT) PathGetDirectory(
 
 /*******************************************************************
 PathGetParentPath - extracts the parent directory from a full path.
+                    *psczDirectory is NULL if the path only contains a file name.
 ********************************************************************/
 DAPI_(HRESULT) PathGetParentPath(
     __in_z LPCWSTR wzPath,
@@ -63,6 +76,21 @@ DAPI_(HRESULT) PathPrefix(
     );
 
 /*******************************************************************
+ PathFixedNormalizeSlashes - replaces all / with \ and
+    removes redundant consecutive slashes.
+********************************************************************/
+DAPI_(HRESULT) PathFixedNormalizeSlashes(
+    __inout_z LPWSTR wzPath
+    );
+
+/*******************************************************************
+ PathFixedReplaceForwardSlashes - replaces all / with \
+********************************************************************/
+DAPI_(void) PathFixedReplaceForwardSlashes(
+    __inout_z LPWSTR wzPath
+    );
+
+/*******************************************************************
  PathFixedBackslashTerminate - appends a \ if path does not have it
                                  already, but fails if the buffer is
                                  insufficient.
@@ -77,7 +105,7 @@ DAPI_(HRESULT) PathFixedBackslashTerminate(
                                  already.
 ********************************************************************/
 DAPI_(HRESULT) PathBackslashTerminate(
-    __inout LPWSTR* psczPath
+    __inout_z LPWSTR* psczPath
     );
 
 /*******************************************************************
@@ -168,7 +196,7 @@ DAPI_(HRESULT) PathGetKnownFolder(
 /*******************************************************************
  PathIsFullyQualified - returns true if the path is fully qualified; false otherwise.
     Note that some rooted paths like C:dir are not fully qualified.
-    For example, these are all fully qualified: C:\dir, \\server\share, \\?\C:\dir.
+    For example, these are all fully qualified: C:\dir, C:/dir, \\server\share, \\?\C:\dir.
     For example, these are not fully qualified: C:dir, C:, \dir, dir, dir\subdir.
 *******************************************************************/
 DAPI_(BOOL) PathIsFullyQualified(
@@ -179,7 +207,7 @@ DAPI_(BOOL) PathIsFullyQualified(
 /*******************************************************************
  PathIsRooted - returns true if the path is rooted; false otherwise.
     Note that some rooted paths like C:dir are not fully qualified.
-    For example, these are all rooted: C:\dir, C:dir, C:, \dir, \\server\share, \\?\C:\dir.
+    For example, these are all rooted: C:\dir, C:/dir, C:dir, C:, \dir, \\server\share, \\?\C:\dir.
     For example, these are not rooted: dir, dir\subdir.
 *******************************************************************/
 DAPI_(BOOL) PathIsRooted(
@@ -240,7 +268,7 @@ DAPI_(HRESULT) PathGetHierarchyArray(
     );
 
 /*******************************************************************
-  PathCanonicalizePath - wrapper around PathCanonicalizeW.
+ PathCanonicalizePath - wrapper around PathCanonicalizeW.
 *******************************************************************/
 DAPI_(HRESULT) PathCanonicalizePath(
     __in_z LPCWSTR wzPath,
@@ -248,8 +276,20 @@ DAPI_(HRESULT) PathCanonicalizePath(
     );
 
 /*******************************************************************
-PathDirectoryContainsPath - checks if wzPath is located inside
-                            wzDirectory.
+ PathCanonicalizeForComparison - canonicalizes the path based on the given flags.
+    . and .. directories are collapsed.
+    All / are replaced with \.
+    All redundant consecutive slashes are replaced with a single \.
+*******************************************************************/
+DAPI_(HRESULT) PathCanonicalizeForComparison(
+    __in_z LPCWSTR wzPath,
+    __in DWORD dwCanonicalizeFlags,
+    __deref_out_z LPWSTR* psczCanonicalized
+    );
+
+/*******************************************************************
+ PathDirectoryContainsPath - checks if wzPath is located inside wzDirectory.
+    wzDirectory must be a fully qualified path.
 *******************************************************************/
 DAPI_(HRESULT) PathDirectoryContainsPath(
     __in_z LPCWSTR wzDirectory,
diff --git a/src/libs/dutil/WixToolset.DUtil/path2utl.cpp b/src/libs/dutil/WixToolset.DUtil/path2utl.cpp
index ff3a946d..45157d0b 100644
--- a/src/libs/dutil/WixToolset.DUtil/path2utl.cpp
+++ b/src/libs/dutil/WixToolset.DUtil/path2utl.cpp
@@ -9,6 +9,7 @@
 #define PathExitWithLastError(x, s, ...) ExitWithLastErrorSource(DUTIL_SOURCE_PATHUTIL, x, s, __VA_ARGS__)
 #define PathExitOnFailure(x, s, ...) ExitOnFailureSource(DUTIL_SOURCE_PATHUTIL, x, s, __VA_ARGS__)
 #define PathExitOnRootFailure(x, s, ...) ExitOnRootFailureSource(DUTIL_SOURCE_PATHUTIL, x, s, __VA_ARGS__)
+#define PathExitWithRootFailure(x, e, s, ...) ExitWithRootFailureSource(DUTIL_SOURCE_PATHUTIL, x, e, s, __VA_ARGS__)
 #define PathExitOnFailureDebugTrace(x, s, ...) ExitOnFailureDebugTraceSource(DUTIL_SOURCE_PATHUTIL, x, s, __VA_ARGS__)
 #define PathExitOnNull(p, x, e, s, ...) ExitOnNullSource(DUTIL_SOURCE_PATHUTIL, p, x, e, s, __VA_ARGS__)
 #define PathExitOnNullWithLastError(p, x, s, ...) ExitOnNullWithLastErrorSource(DUTIL_SOURCE_PATHUTIL, p, x, s, __VA_ARGS__)
@@ -42,63 +43,141 @@ LExit:
     return hr;
 }
 
-DAPI_(HRESULT) PathDirectoryContainsPath(
-    __in_z LPCWSTR wzDirectory,
-    __in_z LPCWSTR wzPath
+DAPI_(HRESULT) PathCanonicalizeForComparison(
+    __in_z LPCWSTR wzPath,
+    __in DWORD dwCanonicalizeFlags,
+    __deref_out_z LPWSTR* psczCanonicalized
     )
 {
     HRESULT hr = S_OK;
-    LPWSTR sczPath = NULL;
-    LPWSTR sczDirectory = NULL;
-    LPWSTR sczOriginalPath = NULL;
-    LPWSTR sczOriginalDirectory = NULL;
+    LPWSTR sczNormalizedPath = NULL;
+    LPCWSTR wzNormalizedPath = NULL;
+    SIZE_T cchUncRootLength = 0;
+    BOOL fHasPrefix = FALSE;
 
-    hr = PathCanonicalizePath(wzPath, &sczOriginalPath);
-    PathExitOnFailure(hr, "Failed to canonicalize the path.");
+    hr = StrAllocString(&sczNormalizedPath, wzPath, 0);
+    PathExitOnFailure(hr, "Failed to allocate string for the normalized path.");
 
-    hr = PathCanonicalizePath(wzDirectory, &sczOriginalDirectory);
-    PathExitOnFailure(hr, "Failed to canonicalize the directory.");
+    PathFixedNormalizeSlashes(sczNormalizedPath);
+
+    wzNormalizedPath = sczNormalizedPath;
 
-    if (!sczOriginalPath || !*sczOriginalPath)
+    if (PATH_CANONICALIZE_KEEP_UNC_ROOT & dwCanonicalizeFlags)
     {
-        ExitFunction1(hr = S_FALSE);
+        if (L'\\' == sczNormalizedPath[0] && (L'\\' == sczNormalizedPath[1] || L'?' == sczNormalizedPath[1]) && L'?' == sczNormalizedPath[2] && L'\\' == sczNormalizedPath[3])
+        {
+            if (L'U' == sczNormalizedPath[4] && L'N' == sczNormalizedPath[5] && L'C' == sczNormalizedPath[6] && L'\\' == sczNormalizedPath[7])
+            {
+                cchUncRootLength = 8;
+            }
+        }
+        else if (L'\\' == sczNormalizedPath[0] && L'\\' == sczNormalizedPath[1])
+        {
+            cchUncRootLength = 2;
+        }
+
+        if (cchUncRootLength)
+        {
+            DWORD dwRemainingSlashes = 2;
+
+            for (wzNormalizedPath += cchUncRootLength; *wzNormalizedPath && dwRemainingSlashes; ++wzNormalizedPath)
+            {
+                ++cchUncRootLength;
+
+                if (L'\\' == *wzNormalizedPath)
+                {
+                    --dwRemainingSlashes;
+                }
+            }
+        }
+    }
+
+    if (*wzNormalizedPath)
+    {
+        hr = PathCanonicalizePath(wzNormalizedPath, psczCanonicalized);
+        PathExitOnFailure(hr, "Failed to canonicalize: %ls", wzNormalizedPath);
     }
-    if (!sczOriginalDirectory || !*sczOriginalDirectory)
+    else
     {
-        ExitFunction1(hr = S_FALSE);
+        Assert(cchUncRootLength);
+        ReleaseStr(*psczCanonicalized);
+        *psczCanonicalized = sczNormalizedPath;
+        sczNormalizedPath = NULL;
+        cchUncRootLength = 0;
     }
 
-    sczPath = sczOriginalPath;
-    sczDirectory = sczOriginalDirectory;
+    if (cchUncRootLength)
+    {
+        hr = StrAllocPrefix(psczCanonicalized, sczNormalizedPath, cchUncRootLength);
+        PathExitOnFailure(hr, "Failed to prefix the UNC root to the canonicalized path.");
+    }
 
-    for (; *sczDirectory;)
+    if (PATH_CANONICALIZE_BACKSLASH_TERMINATE & dwCanonicalizeFlags)
     {
-        if (!*sczPath)
-        {
-            ExitFunction1(hr = S_FALSE);
-        }
+        hr = PathBackslashTerminate(psczCanonicalized);
+        PathExitOnFailure(hr, "Failed to backslash terminate the canonicalized path");
+    }
 
-        if (CSTR_EQUAL != ::CompareStringW(LOCALE_NEUTRAL, NORM_IGNORECASE, sczDirectory, 1, sczPath, 1))
-        {
-            ExitFunction1(hr = S_FALSE);
-        }
+    if ((PATH_CANONICALIZE_APPEND_LONG_PATH_PREFIX & dwCanonicalizeFlags) &&
+        PathIsFullyQualified(*psczCanonicalized, &fHasPrefix) && !fHasPrefix)
+    {
+        hr = PathPrefix(psczCanonicalized);
+        PathExitOnFailure(hr, "Failed to ensure the long path prefix on the canonicalized path");
+    }
+
+LExit:
+    ReleaseStr(sczNormalizedPath);
 
-        ++sczDirectory;
-        ++sczPath;
+    return hr;
+}
+
+DAPI_(HRESULT) PathDirectoryContainsPath(
+    __in_z LPCWSTR wzDirectory,
+    __in_z LPCWSTR wzPath
+    )
+{
+    HRESULT hr = S_OK;
+    LPWSTR sczCanonicalizedDirectory = NULL;
+    LPWSTR sczCanonicalizedPath = NULL;
+    DWORD dwDefaultFlags = PATH_CANONICALIZE_APPEND_LONG_PATH_PREFIX | PATH_CANONICALIZE_KEEP_UNC_ROOT;
+    size_t cchDirectory = 0;
+
+    if (!wzDirectory || !*wzDirectory)
+    {
+        PathExitWithRootFailure(hr, E_INVALIDARG, "wzDirectory is required.");
     }
+    if (!wzPath || !*wzPath)
+    {
+        PathExitWithRootFailure(hr, E_INVALIDARG, "wzPath is required.");
+    }
+
+    hr = PathCanonicalizeForComparison(wzDirectory, dwDefaultFlags | PATH_CANONICALIZE_BACKSLASH_TERMINATE, &sczCanonicalizedDirectory);
+    PathExitOnFailure(hr, "Failed to canonicalize the directory.");
 
-    --sczDirectory;
-    if (('\\' == *sczDirectory && *sczPath) || '\\' == *sczPath)
+    hr = PathCanonicalizeForComparison(wzPath, dwDefaultFlags, &sczCanonicalizedPath);
+    PathExitOnFailure(hr, "Failed to canonicalize the path.");
+
+    if (!PathIsFullyQualified(sczCanonicalizedDirectory, NULL))
     {
-        hr = S_OK;
+        PathExitWithRootFailure(hr, E_INVALIDARG, "wzDirectory must be a fully qualified path.");
     }
-    else
+    if (!sczCanonicalizedPath || !*sczCanonicalizedPath)
     {
-        hr = S_FALSE;
+        ExitFunction1(hr = S_FALSE);
     }
 
+    hr = ::StringCchLengthW(sczCanonicalizedDirectory, STRSAFE_MAX_CCH, &cchDirectory);
+    PathExitOnFailure(hr, "Failed to get length of canonicalized directory.");
+
+    if (CSTR_EQUAL != ::CompareStringW(LOCALE_NEUTRAL, NORM_IGNORECASE, sczCanonicalizedDirectory, (DWORD)cchDirectory, sczCanonicalizedPath, (DWORD)cchDirectory))
+    {
+        ExitFunction1(hr = S_FALSE);
+    }
+
+    hr = sczCanonicalizedPath[cchDirectory] ? S_OK : S_FALSE;
+
 LExit:
-    ReleaseStr(sczOriginalPath);
-    ReleaseStr(sczOriginalDirectory);
+    ReleaseStr(sczCanonicalizedPath);
+    ReleaseStr(sczCanonicalizedDirectory);
     return hr;
 }
diff --git a/src/libs/dutil/WixToolset.DUtil/pathutil.cpp b/src/libs/dutil/WixToolset.DUtil/pathutil.cpp
index 314eab85..99be003c 100644
--- a/src/libs/dutil/WixToolset.DUtil/pathutil.cpp
+++ b/src/libs/dutil/WixToolset.DUtil/pathutil.cpp
@@ -20,6 +20,9 @@
 
 #define PATH_GOOD_ENOUGH 64
 
+static BOOL IsPathSeparatorChar(
+    __in WCHAR wc
+    );
 static BOOL IsValidDriveChar(
     __in WCHAR wc
     );
@@ -41,7 +44,7 @@ DAPI_(LPWSTR) PathFile(
         //     \ => Windows path
         //     / => unix and URL path
         //     : => relative path from mapped root
-        if (L'\\' == *wz || L'/' == *wz || (L':' == *wz && wz == wzPath + 1))
+        if (IsPathSeparatorChar(*wz) || (L':' == *wz && wz == wzPath + 1))
         {
             wzFile = wz + 1;
         }
@@ -64,7 +67,7 @@ DAPI_(LPCWSTR) PathExtension(
     LPCWSTR wzExtension = NULL;
     for (LPCWSTR wz = wzPath; *wz; ++wz)
     {
-        if (L'\\' == *wz || L'/' == *wz || L':' == *wz)
+        if (IsPathSeparatorChar(*wz) || L':' == *wz)
         {
             wzExtension = NULL;
         }
@@ -84,7 +87,8 @@ DAPI_(HRESULT) PathGetDirectory(
     )
 {
     HRESULT hr = S_OK;
-    size_t cchDirectory = SIZE_T_MAX;
+    LPCWSTR wzRemaining = NULL;
+    SIZE_T cchDirectory = 0;
 
     for (LPCWSTR wz = wzPath; *wz; ++wz)
     {
@@ -92,18 +96,20 @@ DAPI_(HRESULT) PathGetDirectory(
         //     \ => Windows path
         //     / => unix and URL path
         //     : => relative path from mapped root
-        if (L'\\' == *wz || L'/' == *wz || (L':' == *wz && wz == wzPath + 1))
+        if (IsPathSeparatorChar(*wz) || (L':' == *wz && wz == wzPath + 1))
         {
-            cchDirectory = static_cast<size_t>(wz - wzPath) + 1;
+            wzRemaining = wz;
         }
     }
 
-    if (SIZE_T_MAX == cchDirectory)
+    if (!wzRemaining)
     {
         // we were given just a file name, so there's no directory available
-        return S_FALSE;
+        ExitFunction1(hr = S_FALSE);
     }
 
+    cchDirectory = static_cast<SIZE_T>(wzRemaining - wzPath) + 1;
+
     hr = StrAllocString(psczDirectory, wzPath, cchDirectory);
     PathExitOnFailure(hr, "Failed to copy directory.");
 
@@ -122,7 +128,7 @@ DAPI_(HRESULT) PathGetParentPath(
 
     for (LPCWSTR wz = wzPath; *wz; ++wz)
     {
-        if (wz[1] && (L'\\' == *wz || L'/' == *wz))
+        if (IsPathSeparatorChar(*wz) && wz[1])
         {
             wzParent = wz;
         }
@@ -291,12 +297,13 @@ DAPI_(HRESULT) PathPrefix(
         hr = StrAllocPrefix(psczFullPath, L"\\\\?\\", 4);
         PathExitOnFailure(hr, "Failed to add prefix to file path.");
     }
-    else if (fFullyQualified && L'\\' == wzFullPath[1]) // UNC
+    else if (fFullyQualified && IsPathSeparatorChar(wzFullPath[1])) // UNC
     {
         hr = StrSize(*psczFullPath, &cbFullPath);
         PathExitOnFailure(hr, "Failed to get size of full path.");
 
         memmove_s(wzFullPath, cbFullPath, wzFullPath + 1, cbFullPath - sizeof(WCHAR));
+        wzFullPath[0] = L'\\';
 
         hr = StrAllocPrefix(psczFullPath, L"\\\\?\\UNC", 7);
         PathExitOnFailure(hr, "Failed to add prefix to UNC path.");
@@ -312,6 +319,90 @@ LExit:
 }
 
 
+DAPI_(HRESULT) PathFixedNormalizeSlashes(
+    __inout_z LPWSTR wzPath
+    )
+{
+    HRESULT hr = S_OK;
+    size_t cchLength = 0;
+    BOOL fAllowDoubleSlash = FALSE;
+    SIZE_T iSource = 0;
+    SIZE_T jDestination = 0;
+
+    hr = ::StringCchLengthW(wzPath, STRSAFE_MAX_CCH, &cchLength);
+    PathExitOnFailure(hr, "Failed to get length of path.");
+
+    if (1 < cchLength && IsPathSeparatorChar(wzPath[0]))
+    {
+        if (IsPathSeparatorChar(wzPath[1]))
+        {
+            // \\?\\a\ is not equivalent to \\?\a\ and \\server\\a\ is not equivalent to \\server\a\.
+            fAllowDoubleSlash = TRUE;
+            wzPath[0] = '\\';
+            wzPath[1] = '\\';
+            iSource = 2;
+            jDestination = 2;
+        }
+        else if (2 < cchLength && L'?' == wzPath[1] && L'?' == wzPath[2])
+        {
+            // \??\\a\ is not equivalent to \??\a\.
+            fAllowDoubleSlash = TRUE;
+            wzPath[0] = '\\';
+            wzPath[1] = '?';
+            wzPath[2] = '?';
+            iSource = 3;
+            jDestination = 3;
+        }
+    }
+
+    for (; iSource < cchLength; ++iSource)
+    {
+        if (IsPathSeparatorChar(wzPath[iSource]))
+        {
+            if (fAllowDoubleSlash)
+            {
+                fAllowDoubleSlash = FALSE;
+            }
+            else if (IsPathSeparatorChar(wzPath[iSource + 1]))
+            {
+                // Skip consecutive slashes.
+                continue;
+            }
+
+            wzPath[jDestination] = '\\';
+        }
+        else
+        {
+            wzPath[jDestination] = wzPath[iSource];
+        }
+
+        ++jDestination;
+    }
+
+    for (; jDestination < cchLength; ++jDestination)
+    {
+        wzPath[jDestination] = '\0';
+    }
+
+LExit:
+    return hr;
+}
+
+
+DAPI_(void) PathFixedReplaceForwardSlashes(
+    __inout_z LPWSTR wzPath
+    )
+{
+    for (LPWSTR wz = wzPath; *wz; ++wz)
+    {
+        if (L'/' == *wz)
+        {
+            *wz = L'\\';
+        }
+    }
+}
+
+
 DAPI_(HRESULT) PathFixedBackslashTerminate(
     __inout_ecount_z(cchPath) LPWSTR wzPath,
     __in SIZE_T cchPath
@@ -320,17 +411,28 @@ DAPI_(HRESULT) PathFixedBackslashTerminate(
     HRESULT hr = S_OK;
     size_t cchLength = 0;
 
+    if (!cchPath)
+    {
+        ExitFunction1(hr = HRESULT_FROM_WIN32(ERROR_INSUFFICIENT_BUFFER));
+    }
+
     hr = ::StringCchLengthW(wzPath, cchPath, &cchLength);
     PathExitOnFailure(hr, "Failed to get length of path.");
 
-    if (cchLength >= cchPath)
+    LPWSTR wzLast = wzPath + (cchLength - 1);
+    if (cchLength && L'/' == wzLast[0])
     {
-        hr = HRESULT_FROM_WIN32(ERROR_INSUFFICIENT_BUFFER);
+        wzLast[0] = L'\\';
     }
-    else if (L'\\' != wzPath[cchLength - 1])
+    else if (!cchLength || L'\\' != wzLast[0])
     {
-        wzPath[cchLength] = L'\\';
-        wzPath[cchLength + 1] = L'\0';
+        if (cchLength + 2 > cchPath)
+        {
+            ExitFunction1(hr = HRESULT_FROM_WIN32(ERROR_INSUFFICIENT_BUFFER));
+        }
+
+        wzLast[1] = L'\\';
+        wzLast[2] = L'\0';
     }
 
 LExit:
@@ -339,10 +441,10 @@ LExit:
 
 
 DAPI_(HRESULT) PathBackslashTerminate(
-    __inout LPWSTR* psczPath
+    __inout_z LPWSTR* psczPath
     )
 {
-    Assert(psczPath && *psczPath);
+    Assert(psczPath);
 
     HRESULT hr = S_OK;
     SIZE_T cchPath = 0;
@@ -354,7 +456,12 @@ DAPI_(HRESULT) PathBackslashTerminate(
     hr = ::StringCchLengthW(*psczPath, cchPath, &cchLength);
     PathExitOnFailure(hr, "Failed to get length of path.");
 
-    if (L'\\' != (*psczPath)[cchLength - 1])
+    LPWSTR wzLast = *psczPath + (cchLength - 1);
+    if (cchLength && L'/' == wzLast[0])
+    {
+        wzLast[0] = L'\\';
+    }
+    else if (!cchLength || L'\\' != wzLast[0])
     {
         hr = StrAllocConcat(psczPath, L"\\", 1);
         PathExitOnFailure(hr, "Failed to concat backslash onto string.");
@@ -833,13 +940,13 @@ DAPI_(BOOL) PathIsFullyQualified(
         ExitFunction();
     }
 
-    if (L'\\' != wzPath[0])
+    if (!IsPathSeparatorChar(wzPath[0]))
     {
         // The only way to specify a fully qualified path that doesn't begin with a slash
         // is the drive, colon, slash format (C:\).
         if (IsValidDriveChar(wzPath[0]) &&
             L':' == wzPath[1] &&
-            L'\\' == wzPath[2])
+            IsPathSeparatorChar(wzPath[2]))
         {
             fFullyQualified = TRUE;
         }
@@ -849,14 +956,14 @@ DAPI_(BOOL) PathIsFullyQualified(
 
     // Non-drive fully qualified paths must start with \\ or \?.
     // \??\ is an archaic form of \\?\.
-    if (L'?' != wzPath[1] && L'\\' != wzPath[1])
+    if (L'?' != wzPath[1] && !IsPathSeparatorChar(wzPath[1]))
     {
         ExitFunction();
     }
 
     fFullyQualified = TRUE;
 
-    if (L'?' == wzPath[2] && L'\\' == wzPath[3])
+    if (L'?' == wzPath[2] && IsPathSeparatorChar(wzPath[3]))
     {
         fHasLongPathPrefix = TRUE;
     }
@@ -877,7 +984,7 @@ DAPI_(BOOL) PathIsRooted(
     )
 {
     return wzPath &&
-        (wzPath[0] == L'\\' ||
+        (IsPathSeparatorChar(wzPath[0]) ||
         IsValidDriveChar(wzPath[0]) && wzPath[1] == L':');
 }
 
@@ -1008,20 +1115,25 @@ DAPI_(HRESULT) PathGetHierarchyArray(
 
     for (size_t i = 0; i < cchPath; ++i)
     {
-        if (wzPath[i] == L'\\')
+        if (IsPathSeparatorChar(wzPath[i]))
         {
             ++cArraySpacesNeeded;
         }
     }
 
-    if (wzPath[cchPath - 1] != L'\\')
+    if (!IsPathSeparatorChar(wzPath[cchPath - 1]))
     {
         ++cArraySpacesNeeded;
     }
 
     // If it's a UNC path, cut off the first three paths, 2 because it starts with a double backslash, and another because the first ("\\servername\") isn't a path.
-    if (wzPath[0] == L'\\' && wzPath[1] == L'\\')
+    if (IsPathSeparatorChar(wzPath[0]) && IsPathSeparatorChar(wzPath[1]))
     {
+        if (3 > cArraySpacesNeeded)
+        {
+            ExitFunction1(hr = E_INVALIDARG);
+        }
+
         cArraySpacesNeeded -= 3;
     }
 
@@ -1042,7 +1154,7 @@ DAPI_(HRESULT) PathGetHierarchyArray(
         DWORD cchPathCopy = lstrlenW(sczPathCopy);
 
         // If it ends in a backslash, it's a directory path, so cut off everything the last backslash before we get the directory portion of the path
-        if (wzPath[cchPathCopy - 1] == L'\\')
+        if (IsPathSeparatorChar(wzPath[cchPathCopy - 1]))
         {
             sczPathCopy[cchPathCopy - 1] = L'\0';
         }
@@ -1063,6 +1175,13 @@ LExit:
     return hr;
 }
 
+static BOOL IsPathSeparatorChar(
+    __in WCHAR wc
+    )
+{
+    return L'/' == wc || L'\\' == wc;
+}
+
 static BOOL IsValidDriveChar(
     __in WCHAR wc
     )
diff --git a/src/libs/dutil/test/DUtilUnitTest/DUtilUnitTest.vcxproj b/src/libs/dutil/test/DUtilUnitTest/DUtilUnitTest.vcxproj
index 1c821a7c..c37bdad1 100644
--- a/src/libs/dutil/test/DUtilUnitTest/DUtilUnitTest.vcxproj
+++ b/src/libs/dutil/test/DUtilUnitTest/DUtilUnitTest.vcxproj
@@ -40,7 +40,7 @@
 
   <PropertyGroup>
     <ProjectAdditionalIncludeDirectories>..\..\WixToolset.DUtil\inc</ProjectAdditionalIncludeDirectories>
-    <ProjectAdditionalLinkLibraries>rpcrt4.lib;Mpr.lib;Ws2_32.lib;urlmon.lib;wininet.lib</ProjectAdditionalLinkLibraries>
+    <ProjectAdditionalLinkLibraries>rpcrt4.lib;Mpr.lib;Ws2_32.lib;shlwapi.lib;urlmon.lib;wininet.lib</ProjectAdditionalLinkLibraries>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/src/libs/dutil/test/DUtilUnitTest/PathUtilTest.cpp b/src/libs/dutil/test/DUtilUnitTest/PathUtilTest.cpp
index 65856514..04d0b447 100644
--- a/src/libs/dutil/test/DUtilUnitTest/PathUtilTest.cpp
+++ b/src/libs/dutil/test/DUtilUnitTest/PathUtilTest.cpp
@@ -12,6 +12,290 @@ namespace DutilTests
     {
     public:
         [Fact]
+        void PathBackslashFixedTerminateTest()
+        {
+            HRESULT hr = S_OK;
+            WCHAR wzEmpty[1] = { L'\0' };
+            WCHAR wzSingleLetter[1] = { L'a' };
+            WCHAR wzSingleBackslash[1] = { L'\\' };
+            WCHAR wzSingleForwardSlash[1] = { L'/' };
+            WCHAR wzSingleLetterNullTerminated[2] = { L'a', L'\0' };
+            WCHAR wzSingleBackslashNullTerminated[2] = { L'\\', L'\0' };
+            WCHAR wzSingleForwardSlashNullTerminated[2] = { L'/', L'\0' };
+            WCHAR wzExtraSpaceLetterNullTerminated[3] = { L'a', L'\0', L'\0' };
+            WCHAR wzExtraSpaceBackslashNullTerminated[3] = { L'\\', L'\0', L'\0' };
+            WCHAR wzExtraSpaceForwardSlashNullTerminated[3] = { L'/', L'\0', L'\0' };
+
+            hr = PathFixedBackslashTerminate(wzEmpty, 0);
+            NativeAssert::SpecificReturnCode(E_INSUFFICIENT_BUFFER, hr, "PathFixedBackslashTerminate: zero-length, {0}", wzEmpty);
+
+            hr = PathFixedBackslashTerminate(wzEmpty, countof(wzEmpty));
+            NativeAssert::SpecificReturnCode(E_INSUFFICIENT_BUFFER, hr, "PathFixedBackslashTerminate: '' (length 1), {0}", wzEmpty);
+
+            hr = PathFixedBackslashTerminate(wzSingleLetter, countof(wzSingleLetter));
+            NativeAssert::SpecificReturnCode(E_INVALIDARG, hr, "PathFixedBackslashTerminate: 'a' (length 1)");
+
+            hr = PathFixedBackslashTerminate(wzSingleBackslash, countof(wzSingleBackslash));
+            NativeAssert::SpecificReturnCode(E_INVALIDARG, hr, "PathFixedBackslashTerminate: '\\' (length 1)");
+
+            hr = PathFixedBackslashTerminate(wzSingleForwardSlash, countof(wzSingleForwardSlash));
+            NativeAssert::SpecificReturnCode(E_INVALIDARG, hr, "PathFixedBackslashTerminate: '/' (length 1)");
+
+            hr = PathFixedBackslashTerminate(wzSingleLetterNullTerminated, countof(wzSingleLetterNullTerminated));
+            NativeAssert::SpecificReturnCode(E_INSUFFICIENT_BUFFER, hr, "PathFixedBackslashTerminate: 'a' (length 2)");
+
+            hr = PathFixedBackslashTerminate(wzSingleBackslashNullTerminated, countof(wzSingleBackslashNullTerminated));
+            NativeAssert::Succeeded(hr, "PathFixedBackslashTerminate: '\\' (length 2)");
+            NativeAssert::StringEqual(L"\\", wzSingleBackslashNullTerminated);
+
+            hr = PathFixedBackslashTerminate(wzSingleForwardSlashNullTerminated, countof(wzSingleForwardSlashNullTerminated));
+            NativeAssert::Succeeded(hr, "PathFixedBackslashTerminate: '/' (length 2)");
+            NativeAssert::StringEqual(L"\\", wzSingleForwardSlashNullTerminated);
+
+            hr = PathFixedBackslashTerminate(wzExtraSpaceLetterNullTerminated, countof(wzExtraSpaceLetterNullTerminated));
+            NativeAssert::Succeeded(hr, "PathFixedBackslashTerminate: 'a' (length 3)");
+            NativeAssert::StringEqual(L"a\\", wzExtraSpaceLetterNullTerminated);
+
+            hr = PathFixedBackslashTerminate(wzExtraSpaceBackslashNullTerminated, countof(wzExtraSpaceBackslashNullTerminated));
+            NativeAssert::Succeeded(hr, "PathFixedBackslashTerminate: '\\' (length 3)");
+            NativeAssert::StringEqual(L"\\", wzExtraSpaceBackslashNullTerminated);
+
+            hr = PathFixedBackslashTerminate(wzExtraSpaceForwardSlashNullTerminated, countof(wzExtraSpaceForwardSlashNullTerminated));
+            NativeAssert::Succeeded(hr, "PathFixedBackslashTerminate: '/' (length 3)");
+            NativeAssert::StringEqual(L"\\", wzExtraSpaceForwardSlashNullTerminated);
+        }
+
+        [Fact]
+        void PathBackslashTerminateTest()
+        {
+            HRESULT hr = S_OK;
+            LPWSTR sczPath = NULL;
+            LPCWSTR rgwzPaths[16] =
+            {
+                L"", L"\\",
+                L"a", L"a\\",
+                L"\\", L"\\",
+                L"a\\", L"a\\",
+                L"/", L"\\",
+                L"a/", L"a\\",
+                L"\\\\", L"\\\\",
+                L"//", L"/\\",
+            };
+
+            try
+            {
+                for (DWORD i = 0; i < countof(rgwzPaths); i += 2)
+                {
+                    hr = StrAllocString(&sczPath, rgwzPaths[i], 0);
+                    NativeAssert::Succeeded(hr, "Failed to copy string");
+
+                    hr = PathBackslashTerminate(&sczPath);
+                    NativeAssert::Succeeded(hr, "PathBackslashTerminate: {0}", rgwzPaths[i]);
+                    NativeAssert::StringEqual(rgwzPaths[i + 1], sczPath);
+                }
+            }
+            finally
+            {
+                ReleaseStr(sczPath);
+            }
+        }
+
+        [Fact]
+        void PathCanonicalizeForComparisonTest()
+        {
+            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);
+
+                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);
+
+                hr = PathCanonicalizeForComparison(L"\\\\server", PATH_CANONICALIZE_KEEP_UNC_ROOT, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"\\\\server", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"\\\\server", 0, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"\\\\server", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"\\\\server\\", PATH_CANONICALIZE_KEEP_UNC_ROOT, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"\\\\server\\", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"\\\\server\\share", PATH_CANONICALIZE_KEEP_UNC_ROOT, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"\\\\server\\share", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"\\\\server\\share\\", PATH_CANONICALIZE_KEEP_UNC_ROOT, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"\\\\server\\share\\", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"\\\\.\\share\\otherdir\\unc.exe", PATH_CANONICALIZE_KEEP_UNC_ROOT, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"\\\\.\\share\\otherdir\\unc.exe", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"\\\\.\\share\\otherdir\\unc.exe", 0, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"\\\\share\\otherdir\\unc.exe", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"\\\\server\\share\\..\\..\\otherdir\\unc.exe", PATH_CANONICALIZE_KEEP_UNC_ROOT, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"\\\\server\\share\\otherdir\\unc.exe", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"\\\\server\\share\\..\\..\\otherdir\\unc.exe", 0, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"\\\\otherdir\\unc.exe", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"\\\\?\\UNC\\server\\share\\..\\..\\otherdir\\unc.exe", PATH_CANONICALIZE_KEEP_UNC_ROOT, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"\\\\?\\UNC\\server\\share\\otherdir\\unc.exe", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"\\\\?\\UNC\\server\\share\\..\\..\\otherdir\\unc.exe", 0, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"\\\\otherdir\\unc.exe", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"C:\\dir\\subdir\\..\\..\\..\\otherdir\\pastroot.exe", 0, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"C:\\otherdir\\pastroot.exe", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"\\\\?\\C:\\dir\\subdir\\..\\..\\..\\otherdir\\pastroot.exe", 0, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"C:\\otherdir\\pastroot.exe", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"\\\\?\\C:dir\\subdir\\..\\..\\..\\otherdir\\pastroot.exe", 0, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"\\otherdir\\pastroot.exe", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"C:dir\\subdir\\..\\..\\..\\otherdir\\pastrelativeroot.exe", 0, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"\\otherdir\\pastrelativeroot.exe", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"A:dir\\subdir\\..\\..\\otherdir\\relativeroot.exe", 0, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"\\otherdir\\relativeroot.exe", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"C:dir\\subdir\\otherdir\\relativeroot.exe", 0, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"C:dir\\subdir\\otherdir\\relativeroot.exe", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"C:\\dir\\subdir\\..\\..\\otherdir\\backslashes.exe", 0, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"C:\\otherdir\\backslashes.exe", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"C:\\dir\\subdir\\..\\..\\otherdir\\\\consecutivebackslashes.exe", 0, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"C:\\otherdir\\consecutivebackslashes.exe", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"C:/dir/subdir/../../otherdir/forwardslashes.exe", 0, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"C:\\otherdir\\forwardslashes.exe", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"\\\\?\\C:\\test\\..\\validlongpath.exe", 0, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"C:\\validlongpath.exe", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"\\\\?\\test\\..\\invalidlongpath.exe", 0, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"\\\\?\\invalidlongpath.exe", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"C:\\.\\invalid:pathchars?.exe", 0, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"C:\\invalid:pathchars?.exe", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"C:\\addprefix.exe", PATH_CANONICALIZE_APPEND_LONG_PATH_PREFIX, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"\\\\?\\C:\\addprefix.exe", sczCanonicalized);
+
+                hr = PathCanonicalizeForComparison(L"C:\\addbackslash.exe", PATH_CANONICALIZE_BACKSLASH_TERMINATE, &sczCanonicalized);
+                NativeAssert::Succeeded(hr, "Failed to canonicalize path");
+                NativeAssert::StringEqual(L"C:\\addbackslash.exe\\", sczCanonicalized);
+            }
+            finally
+            {
+                ReleaseStr(sczCanonicalized);
+            }
+        }
+
+        [Fact]
+        void PathDirectoryContainsPathTest()
+        {
+            HRESULT hr = S_OK;
+
+            hr = PathDirectoryContainsPath(L"", L"");
+            Assert::Equal<HRESULT>(E_INVALIDARG, hr);
+
+            hr = PathDirectoryContainsPath(L"C:\\Directory", L"");
+            Assert::Equal<HRESULT>(E_INVALIDARG, hr);
+
+            hr = PathDirectoryContainsPath(L"", L"C:\\Directory");
+            Assert::Equal<HRESULT>(E_INVALIDARG, hr);
+
+            hr = PathDirectoryContainsPath(L"C:\\Directory", L"C:\\Directory");
+            Assert::Equal<HRESULT>(S_FALSE, hr);
+
+            hr = PathDirectoryContainsPath(L"C:\\Dir", L"C:\\Directory");
+            Assert::Equal<HRESULT>(S_FALSE, hr);
+
+            hr = PathDirectoryContainsPath(L"C:\\Directory", L"C:\\");
+            Assert::Equal<HRESULT>(S_FALSE, hr);
+
+            hr = PathDirectoryContainsPath(L"C:\\Directory", L"C:\\DirectoryPlus");
+            Assert::Equal<HRESULT>(S_FALSE, hr);
+
+            hr = PathDirectoryContainsPath(L"C:\\Directory\\", L"C:\\DirectoryPlus");
+            Assert::Equal<HRESULT>(S_FALSE, hr);
+
+            hr = PathDirectoryContainsPath(L"C:\\Directory\\", L"C:\\Directory\\../Plus");
+            Assert::Equal<HRESULT>(S_FALSE, hr);
+
+            hr = PathDirectoryContainsPath(L"C:\\Directory\\", L"C:\\Directory/../Plus");
+            Assert::Equal<HRESULT>(S_FALSE, hr);
+
+            hr = PathDirectoryContainsPath(L"\\\\server\\share\\Directory", L"\\\\server\\share\\DirectoryPlus");
+            Assert::Equal<HRESULT>(S_FALSE, hr);
+
+            hr = PathDirectoryContainsPath(L"\\\\server\\share\\Directory", L"\\\\discarded\\..\\server\\share\\Directory\\Plus");
+            Assert::Equal<HRESULT>(S_FALSE, hr);
+
+            hr = PathDirectoryContainsPath(L"..\\..", L"..\\..\\plus");
+            Assert::Equal<HRESULT>(E_INVALIDARG, hr);
+
+            hr = PathDirectoryContainsPath(L"..\\..", L"\\..\\..\\plus");
+            Assert::Equal<HRESULT>(E_INVALIDARG, hr);
+
+            hr = PathDirectoryContainsPath(L"\\..\\..", L"\\..\\..\\plus");
+            Assert::Equal<HRESULT>(E_INVALIDARG, hr);
+
+            hr = PathDirectoryContainsPath(L"C:..\\..", L"C:..\\..\\plus");
+            Assert::Equal<HRESULT>(E_INVALIDARG, hr);
+
+            hr = PathDirectoryContainsPath(L"\\\\server\\share\\Directory", L"\\\\server\\share\\Directory\\Plus");
+            Assert::Equal<HRESULT>(S_OK, hr);
+
+            hr = PathDirectoryContainsPath(L"C:\\Directory", L"C:\\directory\\plus");
+            Assert::Equal<HRESULT>(S_OK, hr);
+
+            hr = PathDirectoryContainsPath(L"C:\\Directory\\", L"C:\\Directory\\Plus");
+            Assert::Equal<HRESULT>(S_OK, hr);
+
+            hr = PathDirectoryContainsPath(L"C:\\Directory", L"C:\\.\\Directory\\Plus");
+            Assert::Equal<HRESULT>(S_OK, hr);
+
+            hr = PathDirectoryContainsPath(L"C:\\Directory", L"C:\\Directory/Plus");
+            Assert::Equal<HRESULT>(S_OK, hr);
+
+            hr = PathDirectoryContainsPath(L"C:\\Directory\\", L"C:\\Directory/Plus");
+            Assert::Equal<HRESULT>(S_OK, hr);
+
+            hr = PathDirectoryContainsPath(L"\\\\?\\C:\\Directory", L"C:\\Directory\\Plus");
+            Assert::Equal<HRESULT>(S_OK, hr);
+        }
+
+        [Fact]
         void PathGetDirectoryTest()
         {
             HRESULT hr = S_OK;
@@ -103,6 +387,57 @@ namespace DutilTests
                 NativeAssert::StringEqual(L"Software\\Microsoft\\", rgsczPaths[1]);
                 NativeAssert::StringEqual(L"Software\\Microsoft\\Windows\\", rgsczPaths[2]);
                 ReleaseNullStrArray(rgsczPaths, cPaths);
+
+                hr = PathGetHierarchyArray(L"c:/foo/bar/bas/a.txt", &rgsczPaths, &cPaths);
+                NativeAssert::Succeeded(hr, "Failed to get parent directories array for regular file path");
+                Assert::Equal<DWORD>(5, cPaths);
+                NativeAssert::StringEqual(L"c:/", rgsczPaths[0]);
+                NativeAssert::StringEqual(L"c:/foo/", rgsczPaths[1]);
+                NativeAssert::StringEqual(L"c:/foo/bar/", rgsczPaths[2]);
+                NativeAssert::StringEqual(L"c:/foo/bar/bas/", rgsczPaths[3]);
+                NativeAssert::StringEqual(L"c:/foo/bar/bas/a.txt", rgsczPaths[4]);
+                ReleaseNullStrArray(rgsczPaths, cPaths);
+
+                hr = PathGetHierarchyArray(L"c:/foo/bar/bas/", &rgsczPaths, &cPaths);
+                NativeAssert::Succeeded(hr, "Failed to get parent directories array for regular directory path");
+                Assert::Equal<DWORD>(4, cPaths);
+                NativeAssert::StringEqual(L"c:/", rgsczPaths[0]);
+                NativeAssert::StringEqual(L"c:/foo/", rgsczPaths[1]);
+                NativeAssert::StringEqual(L"c:/foo/bar/", rgsczPaths[2]);
+                NativeAssert::StringEqual(L"c:/foo/bar/bas/", rgsczPaths[3]);
+                ReleaseNullStrArray(rgsczPaths, cPaths);
+
+                hr = PathGetHierarchyArray(L"//server/share/subdir/file.txt", &rgsczPaths, &cPaths);
+                NativeAssert::Succeeded(hr, "Failed to get parent directories array for UNC file path");
+                Assert::Equal<DWORD>(3, cPaths);
+                NativeAssert::StringEqual(L"//server/share/", rgsczPaths[0]);
+                NativeAssert::StringEqual(L"//server/share/subdir/", rgsczPaths[1]);
+                NativeAssert::StringEqual(L"//server/share/subdir/file.txt", rgsczPaths[2]);
+                ReleaseNullStrArray(rgsczPaths, cPaths);
+
+                hr = PathGetHierarchyArray(L"//server/share/subdir/", &rgsczPaths, &cPaths);
+                NativeAssert::Succeeded(hr, "Failed to get parent directories array for UNC directory path");
+                Assert::Equal<DWORD>(2, cPaths);
+                NativeAssert::StringEqual(L"//server/share/", rgsczPaths[0]);
+                NativeAssert::StringEqual(L"//server/share/subdir/", rgsczPaths[1]);
+                ReleaseNullStrArray(rgsczPaths, cPaths);
+
+                hr = PathGetHierarchyArray(L"Software/Microsoft/Windows/ValueName", &rgsczPaths, &cPaths);
+                NativeAssert::Succeeded(hr, "Failed to get parent directories array for UNC directory path");
+                Assert::Equal<DWORD>(4, cPaths);
+                NativeAssert::StringEqual(L"Software/", rgsczPaths[0]);
+                NativeAssert::StringEqual(L"Software/Microsoft/", rgsczPaths[1]);
+                NativeAssert::StringEqual(L"Software/Microsoft/Windows/", rgsczPaths[2]);
+                NativeAssert::StringEqual(L"Software/Microsoft/Windows/ValueName", rgsczPaths[3]);
+                ReleaseNullStrArray(rgsczPaths, cPaths);
+
+                hr = PathGetHierarchyArray(L"Software/Microsoft/Windows/", &rgsczPaths, &cPaths);
+                NativeAssert::Succeeded(hr, "Failed to get parent directories array for UNC directory path");
+                Assert::Equal<DWORD>(3, cPaths);
+                NativeAssert::StringEqual(L"Software/", rgsczPaths[0]);
+                NativeAssert::StringEqual(L"Software/Microsoft/", rgsczPaths[1]);
+                NativeAssert::StringEqual(L"Software/Microsoft/Windows/", rgsczPaths[2]);
+                ReleaseNullStrArray(rgsczPaths, cPaths);
             }
             finally
             {
@@ -111,11 +446,65 @@ namespace DutilTests
         }
 
         [Fact]
+        void PathNormalizeSlashesFixedTest()
+        {
+            HRESULT hr = S_OK;
+            LPWSTR sczPath = NULL;
+            LPCWSTR rgwzPaths[54] =
+            {
+                L"", L"",
+                L"\\", L"\\",
+                L"\\\\", L"\\\\",
+                L"\\\\\\", L"\\\\\\",
+                L"\\\\?\\UNC\\", L"\\\\?\\UNC\\",
+                L"C:\\\\foo2", L"C:\\foo2",
+                L"\\\\?\\C:\\\\foo2", L"\\\\?\\C:\\foo2",
+                L"\\\\a\\b\\", L"\\\\a\\b\\",
+                L"\\\\?\\UNC\\a\\b\\\\c\\", L"\\\\?\\UNC\\a\\b\\c\\",
+                L"\\\\?\\UNC\\a\\b\\\\", L"\\\\?\\UNC\\a\\b\\",
+                L"\\\\?\\UNC\\test\\unc\\path\\to\\\\something", L"\\\\?\\UNC\\test\\unc\\path\\to\\something",
+                L"\\\\?\\C:\\\\foo\\\\bar.txt", L"\\\\?\\C:\\foo\\bar.txt",
+                L"\\??\\C:\\\\foo\\bar.txt", L"\\??\\C:\\foo\\bar.txt",
+                L"\\??\\\\C:\\\\foo\\bar.txt", L"\\??\\\\C:\\foo\\bar.txt",
+                L"/", L"\\",
+                L"//", L"\\\\",
+                L"///", L"\\\\\\",
+                L"//?/UNC/", L"\\\\?\\UNC\\",
+                L"C://foo2", L"C:\\foo2",
+                L"//?/C://foo2", L"\\\\?\\C:\\foo2",
+                L"//a/b/", L"\\\\a\\b\\",
+                L"//?/UNC/a/b//c/", L"\\\\?\\UNC\\a\\b\\c\\",
+                L"//?/UNC/a/b//", L"\\\\?\\UNC\\a\\b\\",
+                L"//?/UNC/test/unc/path/to//something", L"\\\\?\\UNC\\test\\unc\\path\\to\\something",
+                L"//?/C://foo//bar.txt", L"\\\\?\\C:\\foo\\bar.txt",
+                L"/??/C://foo/bar.txt", L"\\??\\C:\\foo\\bar.txt",
+                L"/??//C://foo/bar.txt", L"\\??\\\\C:\\foo\\bar.txt",
+            };
+
+            try
+            {
+                for (DWORD i = 0; i < countof(rgwzPaths); i += 2)
+                {
+                    hr = StrAllocString(&sczPath, rgwzPaths[i], 0);
+                    NativeAssert::Succeeded(hr, "Failed to copy string");
+
+                    hr = PathFixedNormalizeSlashes(sczPath);
+                    NativeAssert::Succeeded(hr, "PathNormalizeSlashes: {0}", rgwzPaths[i]);
+                    NativeAssert::StringEqual(rgwzPaths[i + 1], sczPath);
+                }
+            }
+            finally
+            {
+                ReleaseStr(sczPath);
+            }
+        }
+
+        [Fact]
         void PathPrefixTest()
         {
             HRESULT hr = S_OK;
             LPWSTR sczPath = NULL;
-            LPCWSTR rgwzPaths[12] =
+            LPCWSTR rgwzPaths[24] =
             {
                 L"\\\\", L"\\\\?\\UNC\\",
                 L"C:\\\\foo2", L"\\\\?\\C:\\\\foo2",
@@ -123,11 +512,17 @@ namespace DutilTests
                 L"\\\\?\\UNC\\test\\unc\\path\\to\\something", L"\\\\?\\UNC\\test\\unc\\path\\to\\something",
                 L"\\\\?\\C:\\foo\\bar.txt", L"\\\\?\\C:\\foo\\bar.txt",
                 L"\\??\\C:\\foo\\bar.txt", L"\\??\\C:\\foo\\bar.txt",
+                L"//", L"\\\\?\\UNC\\",
+                L"C://foo2", L"\\\\?\\C://foo2",
+                L"//a/b/", L"\\\\?\\UNC\\a/b/",
+                L"//?/UNC/test/unc/path/to/something", L"//?/UNC/test/unc/path/to/something",
+                L"//?/C:/foo/bar.txt", L"//?/C:/foo/bar.txt",
+                L"/??/C:/foo/bar.txt", L"/??/C:/foo/bar.txt",
             };
 
             try
             {
-                for (DWORD i = 0; i < countof(rgwzPaths) / 2; i += 2)
+                for (DWORD i = 0; i < countof(rgwzPaths); i += 2)
                 {
                     hr = StrAllocString(&sczPath, rgwzPaths[i], 0);
                     NativeAssert::Succeeded(hr, "Failed to copy string");
@@ -148,16 +543,20 @@ namespace DutilTests
         {
             HRESULT hr = S_OK;
             LPWSTR sczPath = NULL;
-            LPCWSTR rgwzPaths[8] =
+            LPCWSTR rgwzPaths[12] =
             {
                 L"\\",
+                L"/",
                 L"C:",
                 L"C:foo.txt",
                 L"",
                 L"\\?",
+                L"/?",
                 L"\\dir",
+                L"/dir",
                 L"dir",
                 L"dir\\subdir",
+                L"dir/subdir",
             };
 
             try
@@ -180,93 +579,162 @@ namespace DutilTests
         [Fact]
         void PathIsRootedAndFullyQualifiedTest()
         {
+            HRESULT hr = S_OK;
+            LPWSTR sczPath = NULL;
             LPCWSTR rgwzPaths[15] =
             {
-                L"\\\\",
-                L"\\\\\\",
-                L"C:\\",
-                L"C:\\\\",
-                L"C:\\foo1",
-                L"C:\\\\foo2",
-                L"\\\\test\\unc\\path\\to\\something",
-                L"\\\\a\\b\\c\\d\\e",
-                L"\\\\a\\b\\",
-                L"\\\\a\\b",
-                L"\\\\test\\unc",
-                L"\\\\Server",
-                L"\\\\Server\\Foo.txt",
-                L"\\\\Server\\Share\\Foo.txt",
-                L"\\\\Server\\Share\\Test\\Foo.txt",
+                L"//",
+                L"///",
+                L"C:/",
+                L"C://",
+                L"C:/foo1",
+                L"C://foo2",
+                L"//test/unc/path/to/something",
+                L"//a/b/c/d/e",
+                L"//a/b/",
+                L"//a/b",
+                L"//test/unc",
+                L"//Server",
+                L"//Server/Foo.txt",
+                L"//Server/Share/Foo.txt",
+                L"//Server/Share/Test/Foo.txt",
             };
 
-            for (DWORD i = 0; i < countof(rgwzPaths); ++i)
+            try
             {
-                ValidateFullyQualifiedPath(rgwzPaths[i], TRUE, FALSE);
-                ValidateRootedPath(rgwzPaths[i], TRUE);
+                for (DWORD i = 0; i < countof(rgwzPaths); ++i)
+                {
+                    ValidateFullyQualifiedPath(rgwzPaths[i], TRUE, FALSE);
+                    ValidateRootedPath(rgwzPaths[i], TRUE);
+
+                    hr = StrAllocString(&sczPath, rgwzPaths[i], 0);
+                    NativeAssert::Succeeded(hr, "Failed to copy string");
+
+                    PathFixedReplaceForwardSlashes(sczPath);
+                    ValidateFullyQualifiedPath(sczPath, TRUE, FALSE);
+                    ValidateRootedPath(sczPath, TRUE);
+                }
+            }
+            finally
+            {
+                ReleaseStr(sczPath);
             }
         }
 
         [Fact]
         void PathIsRootedAndFullyQualifiedWithPrefixTest()
         {
+            HRESULT hr = S_OK;
+            LPWSTR sczPath = NULL;
             LPCWSTR rgwzPaths[6] =
             {
-                L"\\\\?\\UNC\\test\\unc\\path\\to\\something",
-                L"\\\\?\\UNC\\test\\unc",
-                L"\\\\?\\UNC\\a\\b1",
-                L"\\\\?\\UNC\\a\\b2\\",
-                L"\\\\?\\C:\\foo\\bar.txt",
-                L"\\??\\C:\\foo\\bar.txt",
+                L"//?/UNC/test/unc/path/to/something",
+                L"//?/UNC/test/unc",
+                L"//?/UNC/a/b1",
+                L"//?/UNC/a/b2/",
+                L"//?/C:/foo/bar.txt",
+                L"/??/C:/foo/bar.txt",
             };
 
-            for (DWORD i = 0; i < countof(rgwzPaths); ++i)
+            try
             {
-                ValidateFullyQualifiedPath(rgwzPaths[i], TRUE, TRUE);
-                ValidateRootedPath(rgwzPaths[i], TRUE);
+                for (DWORD i = 0; i < countof(rgwzPaths); ++i)
+                {
+                    ValidateFullyQualifiedPath(rgwzPaths[i], TRUE, TRUE);
+                    ValidateRootedPath(rgwzPaths[i], TRUE);
+
+                    hr = StrAllocString(&sczPath, rgwzPaths[i], 0);
+                    NativeAssert::Succeeded(hr, "Failed to copy string");
+
+                    PathFixedReplaceForwardSlashes(sczPath);
+                    ValidateFullyQualifiedPath(sczPath, TRUE, TRUE);
+                    ValidateRootedPath(sczPath, TRUE);
+                }
+            }
+            finally
+            {
+                ReleaseStr(sczPath);
             }
         }
 
         [Fact]
         void PathIsRootedButNotFullyQualifiedTest()
         {
+            HRESULT hr = S_OK;
+            LPWSTR sczPath = NULL;
             LPCWSTR rgwzPaths[7] =
             {
-                L"\\",
+                L"/",
                 L"a:",
                 L"A:",
                 L"z:",
                 L"Z:",
                 L"C:foo.txt",
-                L"\\dir",
+                L"/dir",
             };
 
-            for (DWORD i = 0; i < countof(rgwzPaths); ++i)
+            try
             {
-                ValidateFullyQualifiedPath(rgwzPaths[i], FALSE, FALSE);
-                ValidateRootedPath(rgwzPaths[i], TRUE);
+                for (DWORD i = 0; i < countof(rgwzPaths); ++i)
+                {
+                    ValidateFullyQualifiedPath(rgwzPaths[i], FALSE, FALSE);
+                    ValidateRootedPath(rgwzPaths[i], TRUE);
+
+                    hr = StrAllocString(&sczPath, rgwzPaths[i], 0);
+                    NativeAssert::Succeeded(hr, "Failed to copy string");
+
+                    PathFixedReplaceForwardSlashes(sczPath);
+                    ValidateFullyQualifiedPath(sczPath, FALSE, FALSE);
+                    ValidateRootedPath(sczPath, TRUE);
+                }
+            }
+            finally
+            {
+                ReleaseStr(sczPath);
             }
         }
 
         [Fact]
         void PathIsNotRootedAndNotFullyQualifiedTest()
         {
+            HRESULT hr = S_OK;
+            LPWSTR sczPath = NULL;
             LPCWSTR rgwzPaths[9] =
             {
                 NULL,
                 L"",
                 L"dir",
-                L"dir\\subdir",
-                L"@:\\foo",  // 064 = @     065 = A
-                L"[:\\\\",   // 091 = [     090 = Z
-                L"`:\\foo ", // 096 = `     097 = a
-                L"{:\\\\",   // 123 = {     122 = z
+                L"dir/subdir",
+                L"@:/foo",  // 064 = @     065 = A
+                L"[://",   // 091 = [     090 = Z
+                L"`:/foo ", // 096 = `     097 = a
+                L"{://",   // 123 = {     122 = z
                 L"[:",
             };
 
-            for (DWORD i = 0; i < countof(rgwzPaths); ++i)
+            try
             {
-                ValidateFullyQualifiedPath(rgwzPaths[i], FALSE, FALSE);
-                ValidateRootedPath(rgwzPaths[i], FALSE);
+                for (DWORD i = 0; i < countof(rgwzPaths); ++i)
+                {
+                    ValidateFullyQualifiedPath(rgwzPaths[i], FALSE, FALSE);
+                    ValidateRootedPath(rgwzPaths[i], FALSE);
+
+                    if (!rgwzPaths[i])
+                    {
+                        continue;
+                    }
+
+                    hr = StrAllocString(&sczPath, rgwzPaths[i], 0);
+                    NativeAssert::Succeeded(hr, "Failed to copy string");
+
+                    PathFixedReplaceForwardSlashes(sczPath);
+                    ValidateFullyQualifiedPath(sczPath, FALSE, FALSE);
+                    ValidateRootedPath(sczPath, FALSE);
+                }
+            }
+            finally
+            {
+                ReleaseStr(sczPath);
             }
         }
 
diff --git a/src/wix/test/WixToolsetTest.CoreIntegration/PayloadFixture.cs b/src/wix/test/WixToolsetTest.CoreIntegration/PayloadFixture.cs
index 5b663d93..a4f6a3fd 100644
--- a/src/wix/test/WixToolsetTest.CoreIntegration/PayloadFixture.cs
+++ b/src/wix/test/WixToolsetTest.CoreIntegration/PayloadFixture.cs
@@ -84,7 +84,7 @@ namespace WixToolsetTest.CoreIntegration
                                                         ? field.AsNullableNumber()?.ToString()
                                                         : field?.AsString())
                                                 .ToList();
-                Assert.Equal(@"c\d.exe", fields[(int)WixBundlePayloadSymbolFields.Name]);
+                Assert.Equal(@"c\d\e\f.exe", fields[(int)WixBundlePayloadSymbolFields.Name]);
             }
         }
 
diff --git a/src/wix/test/WixToolsetTest.CoreIntegration/TestData/Payload/CanonicalizeName.wxs b/src/wix/test/WixToolsetTest.CoreIntegration/TestData/Payload/CanonicalizeName.wxs
index 544b80ec..a6f3b453 100644
--- a/src/wix/test/WixToolsetTest.CoreIntegration/TestData/Payload/CanonicalizeName.wxs
+++ b/src/wix/test/WixToolsetTest.CoreIntegration/TestData/Payload/CanonicalizeName.wxs
@@ -1,7 +1,7 @@
 <Wix xmlns="http://wixtoolset.org/schemas/v4/wxs">
     <Fragment>
         <PayloadGroup Id="CanonicalizeName">
-            <Payload SourceFile="dir\file.ext" Name="a\..\c\.\d.exe" />
+            <Payload SourceFile="dir\file.ext" Name="a\..\c\.\d/e\\f.exe" />
         </PayloadGroup>
     </Fragment>
 </Wix>