fix: resolve 14 code-review issues across Core/Differential/Bowl/Drivelution/Extension

src/c#/GeneralUpdate.Bowl/Strategies/LinuxBowlStrategy.cs

@@ -275,8 +275,10 @@ private static string DetectDistro()
 
     private static void EnsureDirectory(string path)
     {
-        if (Directory.Exists(path))
-            Directory.Delete(path, recursive: true);
-        Directory.CreateDirectory(path);
+        // Create the fail directory if it does not yet exist.
+        // Do NOT delete an existing directory — that would destroy
+        // crash diagnostics from previous surveillance sessions.
+        if (!Directory.Exists(path))
+            Directory.CreateDirectory(path);
     }
 }

src/c#/GeneralUpdate.Bowl/Strategies/ProcessRunner.cs

@@ -28,6 +28,7 @@ public static async Task<ProcessExitResult> RunAsync(
         var outputLines = new List<string>();
 
         using var process = new Process { StartInfo = startInfo };
+        using var timeoutCts = CancellationTokenSource.CreateLinkedTokenSource(ct);
         var tcs = new TaskCompletionSource<int>(TaskCreationOptions.RunContinuationsAsynchronously);
 
         process.OutputDataReceived += (_, e) =>
@@ -61,14 +62,17 @@ public static async Task<ProcessExitResult> RunAsync(
         process.BeginOutputReadLine();
         process.BeginErrorReadLine();
 
-        // Wait for exit or timeout/cancellation
-        var completedTask = await Task.WhenAny(
-            tcs.Task,
-            Task.Delay(timeoutMs, ct)
-        );
+        // Wait for exit or timeout/cancellation.
+        // Cancel the delay when the process exits first to avoid a timer leak.
+        var delayTask = Task.Delay(timeoutMs, timeoutCts.Token);
+        var completedTask = await Task.WhenAny(tcs.Task, delayTask);
+
+        // Cancel the opposing task so timers/resources are reclaimed promptly.
+        timeoutCts.Cancel();
 
         if (completedTask == tcs.Task)
         {
+            try { await delayTask; } catch (OperationCanceledException) { /* cancelled — expected */ }
             var exitCode = await tcs.Task;
             GeneralTracer.Info($"ProcessRunner.RunAsync: process exited, ExitCode={exitCode}");
             // Snapshot output under lock to avoid race with in-flight handlers

src/c#/GeneralUpdate.Bowl/Strategies/WindowsBowlStrategy.cs

@@ -63,8 +63,10 @@ public Task PostProcessAsync(in BowlContext context,
 
     private static void EnsureDirectory(string path)
     {
-        if (Directory.Exists(path))
-            StorageHelper.DeleteDirectory(path);
-        Directory.CreateDirectory(path);
+        // Create the fail directory if it does not yet exist.
+        // Do NOT delete an existing directory — that would destroy
+        // crash diagnostics from previous surveillance sessions.
+        if (!Directory.Exists(path))
+            Directory.CreateDirectory(path);
     }
 }

src/c#/GeneralUpdate.Core/Event/EventManager.cs

@@ -119,9 +119,15 @@ public void Dispatch<TEventArgs>(object sender, TEventArgs eventArgs) where TEve
             var type = typeof(Action<object, TEventArgs>);
             if (_dicDelegates.TryGetValue(type, out var existingDelegate))
             {
+                // Snapshot the delegate invocation list to avoid a race with
+                // concurrent AddListener / RemoveListener mutating the delegate
+                // while we enumerate it. The ConcurrentDictionary protects the
+                // dictionary structure but not the Delegate value itself.
+                var invocationList = existingDelegate.GetInvocationList();
+
                 // Invoke each handler individually so one handler's exception
                 // doesn't prevent others from being called.
-                foreach (var handler in existingDelegate.GetInvocationList())
+                foreach (var handler in invocationList)
                 {
                     try
                     {

src/c#/GeneralUpdate.Core/FileSystem/FileNode.cs

@@ -232,8 +232,7 @@ public FileNode SearchParent(long id)
     public override bool Equals(object obj)
     {
         if (obj == null) return false;
-        var tempNode = obj as FileNode;
-        if (tempNode == null) throw new ArgumentException(nameof(tempNode));
+        if (obj is not FileNode tempNode) return false;
         return string.Equals(Hash, tempNode.Hash, StringComparison.OrdinalIgnoreCase) &&
                string.Equals(Name, tempNode.Name, StringComparison.OrdinalIgnoreCase);
     }

src/c#/GeneralUpdate.Core/FileSystem/FileTree.cs

@@ -209,23 +209,23 @@ public void Compare(FileNode node, FileNode node0, ref List<FileNode> nodes)
             if (node != null && node.Left != null)
             {
                 if (!node.Equals(node0) && node0 != null) nodes.Add(node0);
-                Compare(node.Left, node0.Left, ref nodes);
+                Compare(node.Left, node0?.Left, ref nodes);
             }
             else if (node0 != null && node0.Left != null)
             {
                 nodes.Add(node0);
-                Compare(node.Left, node0.Left, ref nodes);
+                Compare(node?.Left, node0.Left, ref nodes);
             }
 
             if (node != null && node.Right != null)
             {
                 if (!node.Equals(node0) && node0 != null) nodes.Add(node0);
-                Compare(node.Right, node0 == null ? null : node0.Right, ref nodes);
+                Compare(node.Right, node0?.Right, ref nodes);
             }
             else if (node0 != null && node0.Right != null)
             {
                 nodes.Add(node0);
-                Compare(node == null ? null : node.Right, node0.Right, ref nodes);
+                Compare(node?.Right, node0.Right, ref nodes);
             }
             else if (node0 != null)
             {

src/c#/GeneralUpdate.Core/Pipeline/DiffPipeline.cs

@@ -222,7 +222,7 @@ public async Task CleanAsync(
         }
 
         int completed = 0;
-        var semaphore = new SemaphoreSlim(_options.MaxDegreeOfParallelism);
+        using var semaphore = new SemaphoreSlim(_options.MaxDegreeOfParallelism);
 
         var tasks = differentFiles.Select(file => Task.Run(async () =>
         {
@@ -342,7 +342,7 @@ public async Task DirtyAsync(
         }
 
         int completed = 0;
-        var semaphore = new SemaphoreSlim(_options.MaxDegreeOfParallelism);
+        using var semaphore = new SemaphoreSlim(_options.MaxDegreeOfParallelism);
 
         var matchedPairs = new List<(FileInfo OldFile, FileInfo PatchFile)>();
         foreach (var oldFile in oldFiles)

src/c#/GeneralUpdate.Core/Strategy/ClientStrategy.cs

@@ -903,7 +903,10 @@ private bool CheckFail(string version)
         var fail = Environments.GetEnvironmentVariable("UpgradeFail");
         if (string.IsNullOrEmpty(fail) || string.IsNullOrEmpty(version))
             return false;
-        return new Version(fail) >= new Version(version);
+        if (!Version.TryParse(fail, out var failVersion) ||
+            !Version.TryParse(version, out var versionParsed))
+            return false;
+        return failVersion >= versionParsed;
     }
 
     /// <summary>

src/c#/GeneralUpdate.Core/Strategy/OssStrategy.cs

@@ -3,6 +3,7 @@
 using System.Diagnostics;
 using System.IO;
 using System.Linq;
+using System.Runtime.InteropServices;
 using System.Text;
 using System.Text.Json;
 using System.Threading.Tasks;
@@ -258,15 +259,25 @@ private async Task ExecuteClientAsync()
             : installPath;
         var upgradeAppName = !string.IsNullOrWhiteSpace(_configInfo.UpdateAppName)
             ? _configInfo.UpdateAppName
-            : "GeneralUpdate.Upgrade.exe";
+            : RuntimeInformation.IsOSPlatform(OSPlatform.Windows)
+                ? "GeneralUpdate.Upgrade.exe"
+                : "GeneralUpdate.Upgrade";
         var appPath = Path.Combine(upgradeDir, upgradeAppName);
         GeneralTracer.Info($"[OssClient] Resolved upgrade path: {appPath}");
 
-        // List exe files in the directory to help diagnose missing file issues
+        // List executables in the directory to help diagnose missing file issues
         try
         {
-            var dirFiles = Directory.GetFiles(upgradeDir, "*.exe").Select(f => Path.GetFileName(f));
-            GeneralTracer.Info($"[OssClient] *.exe files in {upgradeDir}: [{string.Join(", ", dirFiles)}]");
+            var searchPattern = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "*.exe" : "*";
+            const int maxDisplay = 20;
+            var dirFiles = Directory.EnumerateFiles(upgradeDir, searchPattern)
+                .Take(maxDisplay + 1)
+                .Select(f => Path.GetFileName(f))
+                .ToList();
+            var summary = dirFiles.Count > maxDisplay
+                ? $"[{string.Join(", ", dirFiles.Take(maxDisplay))}, ... and {dirFiles.Count - maxDisplay} more]"
+                : $"[{string.Join(", ", dirFiles)}]";
+            GeneralTracer.Info($"[OssClient] Files in {upgradeDir}: {summary}");
         }
         catch (Exception ex)
         {

src/c#/GeneralUpdate.Core/Tracer/GeneralTracer.cs

@@ -34,27 +34,30 @@ static GeneralTracer()
 
     private static void InitializeFileListener()
     {
-        //Ensure that log files are rotated on a daily basis
-        var today = DateTime.Now.ToString("yyyy-MM-dd");
-        if (today == _currentLogDate && _fileListener != null)
-            return;
-
-        if (_fileListener != null)
+        lock (_lockObj)
         {
-            Trace.Listeners.Remove(_fileListener);
-            _fileListener.Flush();
-            _fileListener.Close();
-            _fileListener.Dispose();
-        }
+            // Ensure that log files are rotated on a daily basis
+            var today = DateTime.Now.ToString("yyyy-MM-dd");
+            if (today == _currentLogDate && _fileListener != null)
+                return;
 
-        var logDir = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "Logs");
-        Directory.CreateDirectory(logDir);
+            if (_fileListener != null)
+            {
+                Trace.Listeners.Remove(_fileListener);
+                _fileListener.Flush();
+                _fileListener.Close();
+                _fileListener.Dispose();
+            }
+
+            var logDir = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "Logs");
+            Directory.CreateDirectory(logDir);
 
-        var logFileName = Path.Combine(logDir, $"generalupdate-trace {today}.log");
-        _fileListener = new TextTraceListener(logFileName);
-
-        Trace.Listeners.Add(_fileListener);
-        _currentLogDate = today;
+            var logFileName = Path.Combine(logDir, $"generalupdate-trace {today}.log");
+            _fileListener = new TextTraceListener(logFileName);
+
+            Trace.Listeners.Add(_fileListener);
+            _currentLogDate = today;
+        }
     }
 
     public static void Debug(string message) => WriteTraceMessage(TraceLevel.Verbose, message);

src/c#/GeneralUpdate.Differential/Differ/BsdiffDiffer.cs

@@ -308,7 +308,9 @@ await Task.Run(() =>
                             byte[] formatByte = ReadExactly(patchStream, 1);
                             byte candidate = formatByte[0];
 
-                            if (candidate == BZip2FormatVersion || candidate == DeflateFormatVersion)
+                            if (candidate == BZip2FormatVersion || candidate == DeflateFormatVersion
+                                || candidate == BrotliFormatVersion
+                               )
                             {
                                 formatVersion = candidate;
                                 actualHeaderSize = ExtendedHeaderSize;
@@ -333,6 +335,9 @@ await Task.Run(() =>
                     {
                         BZip2FormatVersion => new BZip2CompressionProvider(),
                         DeflateFormatVersion => new DeflateCompressionProvider(),
+#if NET6_0_OR_GREATER
+                        BrotliFormatVersion => new BrotliCompressionProvider(),
+#endif
                         _ => throw new InvalidOperationException(
                             $"Unsupported patch compression format version: 0x{formatVersion:X2}")
                     };
@@ -437,6 +442,7 @@ await Task.Run(() =>
 
         private const byte BZip2FormatVersion = 0x00;
         private const byte DeflateFormatVersion = 0x01;
+        private const byte BrotliFormatVersion = 0x02;
 
         private static FileStream OpenPatchStream(string patchPath)
         {
@@ -477,17 +483,19 @@ private static int Search(int[] I, byte[] oldData, byte[] newData, int newOffset
         {
             if (end - start < 2)
             {
-                int x = MatchLength(oldData, I[start], newData, newOffset);
-                int y = MatchLength(oldData, I[end], newData, newOffset);
+                // Guard against sentinel -1 values that Split() writes for singleton buckets.
+                // MatchLength with a negative index would throw IndexOutOfRangeException.
+                int x = I[start] >= 0 ? MatchLength(oldData, I[start], newData, newOffset) : 0;
+                int y = I[end]   >= 0 ? MatchLength(oldData, I[end],   newData, newOffset) : 0;
 
                 if (x > y)
                 {
-                    pos = I[start];
+                    pos = I[start] >= 0 ? I[start] : 0;
                     return x;
                 }
                 else
                 {
-                    pos = I[end];
+                    pos = I[end] >= 0 ? I[end] : 0;
                     return y;
                 }
             }

src/c#/GeneralUpdate.Differential/Differ/StreamingHdiffDiffer.cs

@@ -436,16 +436,20 @@ private static void ValidatePaths(string oldPath, string newPath, string patchPa
         private static byte[] ReadFileWithBudget(string path, int maxBytes)
         {
             byte[] buffer = new byte[maxBytes];
+            int totalRead = 0;
             using (var fs = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read))
             {
-                int totalRead = 0;
                 while (totalRead < maxBytes)
                 {
                     int read = fs.Read(buffer, totalRead, maxBytes - totalRead);
                     if (read == 0) break;
                     totalRead += read;
                 }
             }
+            // Trim to actual bytes read so callers using .Length see the real data,
+            // not zero-initialized tail bytes that would corrupt patch computation.
+            if (totalRead < maxBytes)
+                Array.Resize(ref buffer, totalRead);
             return buffer;
         }