Fix #84344 to ensure sufficient stack by calling RuntimeHelpers.EnsureSufficientExecutionStack()

src/libraries/System.Private.CoreLib/src/System/IO/FileSystem.Unix.cs

@@ -4,6 +4,7 @@
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO.Enumeration;
+using System.Runtime.CompilerServices;
 using System.Text;
 using Microsoft.Win32.SafeHandles;
 
@@ -496,6 +497,8 @@ private static void RemoveDirectoryRecursive(string fullPath)
                     {
                         if (isDirectory)
                         {
+                            // Since this is a recursive call, we have to ensure that we have sufficient stack space.
+                            RuntimeHelpers.EnsureSufficientExecutionStack();
                             RemoveDirectoryRecursive(childPath);
                         }
                         else

src/libraries/System.Private.CoreLib/src/System/IO/FileSystem.Windows.cs

@@ -4,6 +4,7 @@
 using System.Buffers;
 using System.ComponentModel;
 using System.Diagnostics;
+using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using Microsoft.Win32.SafeHandles;
 
@@ -344,6 +345,8 @@ private static void RemoveDirectoryRecursive(string fullPath, ref Interop.Kernel
                             // Not a reparse point, or the reparse point isn't a name surrogate, recurse.
                             try
                             {
+                                // Since this is a recursive call, we have to ensure that we have sufficient stack space.
+                                RuntimeHelpers.EnsureSufficientExecutionStack();
                                 RemoveDirectoryRecursive(
                                     Path.Combine(fullPath, fileName),
                                     findData: ref findData,

src/libraries/System.Runtime/tests/System.IO.FileSystem.Tests/Directory/Delete.cs

@@ -288,6 +288,24 @@
             Delete(rootDirectory, recursive: true);
         }
 
+        [Fact]
+        [PlatformSpecific(TestPlatforms.Windows)]
+        public void RecursiveDelete_Issue84344()
+        {
+            // Test the scenario described in GitHub issue #84344 where the nesting depth of subdirectories is huge (14000).
+            // Using 14000 as the depth makes the test very slow, so we reduce the depth to 9000 for quicker execution while still
+            // exercising a very deep directory tree. See https://github.com/dotnet/runtime/issues/84344.
+            // The original scenario and this test are limited to Windows; on Unix-like systems the much shorter maximum path length
+            // (for example, 4096 characters) would cause failures due to path length limits rather than testing Directory.Delete recursion.
+            DirectoryInfo subDir = testDir.CreateSubdirectory("test_issue84344");
+            for (int i = 0; i < depth; i++)
+            {
+                subDir = subDir.CreateSubdirectory("a");
+            }
+            // Now delete the subdir recursively.
+            Directory.Delete(subDir.FullName, recursive: true);
+        }
+
         [Fact]
         [PlatformSpecific(TestPlatforms.Windows)]  // Recursive delete throws IOException if directory contains in-use file
         public void RecursiveDelete_ShouldThrowIOExceptionIfContainedFileInUse()