From 78b0139bc3b2abb3038fff1fbdd66c3babdbd1e8 Mon Sep 17 00:00:00 2001
From: safocl <safocl88@gmail.com>
Date: Sun, 4 Jan 2026 15:33:16 +0400
Subject: [PATCH] powerrename: fix union usage (#42845)

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fix/what does it change/how was it tested (even manually, if necessary)?
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## Summary of the Pull Request

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## PR Checklist

- [x] Closes: #42843
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [x] **Tests:** Added/updated and all pass

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or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments
fix undefined behavior when using union in the `IFACEMETHODIMP
CPowerRenameRegEx::PutFileTime(_In_ SYSTEMTIME fileTime)` function

https://github.com/microsoft/PowerToys/blob/a69f7fa806539e0de6e9e901b4f651c512fdd54f/src/modules/powerrename/lib/PowerRenameRegEx.cpp#L299

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wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed
---
 src/modules/powerrename/lib/PowerRenameRegEx.cpp | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/src/modules/powerrename/lib/PowerRenameRegEx.cpp b/src/modules/powerrename/lib/PowerRenameRegEx.cpp
index aabf838a7a..e9ce4fa62a 100644
--- a/src/modules/powerrename/lib/PowerRenameRegEx.cpp
+++ b/src/modules/powerrename/lib/PowerRenameRegEx.cpp
@@ -344,19 +344,13 @@ IFACEMETHODIMP CPowerRenameRegEx::PutFlags(_In_ DWORD flags)
 
 IFACEMETHODIMP CPowerRenameRegEx::PutFileTime(_In_ SYSTEMTIME fileTime)
 {
-    union timeunion
-    {
-        FILETIME fileTime;
-        ULARGE_INTEGER ul;
-    };
+    FILETIME ft1;
+    FILETIME ft2;
 
-    timeunion ft1;
-    timeunion ft2;
+    SystemTimeToFileTime(&m_fileTime, &ft1);
+    SystemTimeToFileTime(&fileTime, &ft2);
 
-    SystemTimeToFileTime(&m_fileTime, &ft1.fileTime);
-    SystemTimeToFileTime(&fileTime, &ft2.fileTime);
-
-    if (ft2.ul.QuadPart != ft1.ul.QuadPart)
+    if (ft2.dwLowDateTime != ft1.dwLowDateTime || ft2.dwHighDateTime != ft1.dwHighDateTime)
     {
         m_fileTime = fileTime;
         m_useFileTime = true;