[KERNEL32_VISTA] Reimplement [Get|Set]ThreadDescription() (#8484)

- `GetThreadDescription()`: since there may be concurrent `SetThreadDescription()`
  invocations being executed, we need to loop over the buffer allocation size until
  we can successfully capture the thread name.
  Also, we can directly re-use the temporary buffer, after resizing, for
  the output description buffer.

- `SetThreadDescription()`: Use `RtlInitUnicodeStringEx()` instead of reimplementing
  its internal logic.

dll/win32/kernel32/kernel32_vista/CMakeLists.txt

@@ -7,8 +7,8 @@ include_directories(${REACTOS_SOURCE_DIR}/sdk/include/reactos/subsys ..)
 spec2def(kernel32_vista.dll kernel32_vista.spec ADD_IMPORTLIB)
 
 list(APPEND SOURCE
-    firmware.c
     EnumSystemLocalesEx.c
+    firmware.c
     GetLocaleInfoEx.c
     GetFileInformationByHandleEx.c
     GetFinalPathNameByHandle.c
@@ -19,8 +19,8 @@ list(APPEND SOURCE
     IsValidLocaleName.c
     LCIDToLocaleName.c
     LocaleNameToLCID.c
-    SetThreadDescription.c
     sync.c
+    ThreadDescription.c
     threadpool.c
     vista.c)
 

dll/win32/kernel32/kernel32_vista/SetThreadDescription.c

@@ -1,28 +0,0 @@
-
-#include "k32_vista.h"
-#define NDEBUG
-#include <debug.h>
-
-#undef TRACE
-#define TRACE DPRINT
-
-/***********************************************************************
- *           SetThreadDescription   (kernelbase.@)
- */
-HRESULT WINAPI DECLSPEC_HOTPATCH SetThreadDescription( HANDLE thread, PCWSTR description )
-{
-    THREAD_NAME_INFORMATION info;
-    int length;
-
-    TRACE( "(%p, %s)\n", thread, debugstr_w( description ));
-
-    length = description ? lstrlenW( description ) * sizeof(WCHAR) : 0;
-
-    if (length > USHRT_MAX)
-        return HRESULT_FROM_NT(STATUS_INVALID_PARAMETER);
-
-    info.ThreadName.Length = info.ThreadName.MaximumLength = length;
-    info.ThreadName.Buffer = (WCHAR *)description;
-
-    return HRESULT_FROM_NT(NtSetInformationThread( thread, ThreadNameInformation, &info, sizeof(info) ));
-}

dll/win32/kernel32/kernel32_vista/ThreadDescription.c

@@ -0,0 +1,93 @@
+/*
+ * PROJECT:     ReactOS Win32 Base API
+ * LICENSE:     GPL-2.0-or-later (https://spdx.org/licenses/GPL-2.0-or-later)
+ * PURPOSE:     NT10+ Thread Description helpers
+ * COPYRIGHT:   Copyright 2025-2026 Hermès Bélusca-Maïto <hermes.belusca-maito@reactos.org>
+ */
+
+#include "k32_vista.h"
+
+HRESULT
+WINAPI
+DECLSPEC_HOTPATCH
+GetThreadDescription(
+    _In_ HANDLE hThread,
+    _Outptr_result_z_ PWSTR* ppszThreadDescription)
+{
+    PTHREAD_NAME_INFORMATION NameInfo = NULL;
+    PVOID ptr;
+    NTSTATUS Status;
+    ULONG Length;
+
+    *ppszThreadDescription = NULL;
+
+    /* Since there may be concurrent SetThreadDescription() invocations being
+     * executed, we need to loop over the buffer allocation size until we can
+     * successfully capture the thread name. */
+    Length = 0;
+    Status = NtQueryInformationThread(hThread, ThreadNameInformation, NULL, 0, &Length);
+    if (Status != STATUS_BUFFER_TOO_SMALL)
+        return HRESULT_FROM_NT(Status);
+
+    /* Loop again only if we get buffer-too-small types of errors;
+     * otherwise, break the loop: any error will be handled below. */
+    while (Status == STATUS_INFO_LENGTH_MISMATCH ||
+           Status == STATUS_BUFFER_TOO_SMALL)
+    {
+        /* (Re-)allocate the information buffer */
+        ptr = (NameInfo ? LocalReAlloc(NameInfo, Length, LMEM_MOVEABLE)
+                        : LocalAlloc(LMEM_FIXED, Length));
+        if (!ptr)
+        {
+            Status = STATUS_NO_MEMORY;
+            break;
+        }
+        NameInfo = ptr;
+        Status = NtQueryInformationThread(hThread, ThreadNameInformation,
+                                          NameInfo, Length, &Length);
+    }
+    if (!NT_SUCCESS(Status))
+    {
+        LocalFree(NameInfo);
+        return HRESULT_FROM_NT(Status);
+    }
+
+    /*
+     * We already have a suitable memory buffer, containing a UNICODE_STRING
+     * followed by the actual string data. Just move the string back to the
+     * beginning of the buffer and resize it down. Since sizeof(UNICODE_STRING)
+     * is larger than sizeof(WCHAR), we also have space for the NUL-terminator.
+     */
+    *ppszThreadDescription = (PWSTR)NameInfo;
+    Length = NameInfo->ThreadName.Length;
+    if (Length)
+        RtlMoveMemory(*ppszThreadDescription, NameInfo->ThreadName.Buffer, Length);
+    (*ppszThreadDescription)[Length / sizeof(WCHAR)] = UNICODE_NULL;
+
+    /* Resize down the buffer. If the call fails, the old buffer
+     * is still valid, but is larger than what is necessary. */
+    ptr = LocalReAlloc(*ppszThreadDescription, Length + sizeof(WCHAR), LMEM_FIXED);
+    if (ptr)
+        *ppszThreadDescription = ptr;
+
+    return HRESULT_FROM_NT(Status);
+}
+
+HRESULT
+WINAPI
+DECLSPEC_HOTPATCH
+SetThreadDescription(
+    _In_ HANDLE hThread,
+    _In_ PCWSTR lpThreadDescription)
+{
+    THREAD_NAME_INFORMATION NameInfo;
+    NTSTATUS Status;
+
+    Status = RtlInitUnicodeStringEx(&NameInfo.ThreadName, lpThreadDescription);
+    if (NT_SUCCESS(Status))
+    {
+        Status = NtSetInformationThread(hThread, ThreadNameInformation,
+                                        &NameInfo, sizeof(NameInfo));
+    }
+    return HRESULT_FROM_NT(Status);
+}

dll/win32/kernel32/kernel32_vista/kernel32_vista.spec

@@ -59,6 +59,7 @@
 @ stdcall CompareStringOrdinal(ptr long ptr long long)
 
 @ stdcall GetNamedPipeClientProcessId(ptr ptr)
+@ stdcall GetThreadDescription(ptr ptr) # Win 10
 @ stdcall SetThreadDescription(ptr wstr) # Win 10
 @ stdcall GetSystemTimePreciseAsFileTime(ptr) kernel32.GetSystemTimeAsFileTime
 @ stdcall TrySubmitThreadpoolCallback(ptr ptr ptr)