From fb3e7825f35ba165a6785fba5e8c5eddbc6aa3f5 Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Fri, 23 May 2025 09:03:03 -0400
Subject: [PATCH] StdIo: Restore Windows Console I/O modes on exit

The Windows documentation [1] states:

> command-line applications should capture the initial console
> mode at startup and attempt to restore it when exiting

We set `ENABLE_VIRTUAL_TERMINAL_{INPUT,PROCESSING}` modes since
commit d6a1ff59f1 (StdIo: Provide metadata about stdin, stdout,
stderr streams, 2025-05-06).  Avoid leaking them.

[1] https://learn.microsoft.com/en-us/windows/console/console-modes

Issue: #26924
---
 Source/cmStdIoStream.cxx | 19 +++++++++++++++----
 Source/cmStdIoStream.h   |  2 ++
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/Source/cmStdIoStream.cxx b/Source/cmStdIoStream.cxx
index 9f448f2c84..4abe6050ec 100644
--- a/Source/cmStdIoStream.cxx
+++ b/Source/cmStdIoStream.cxx
@@ -115,17 +115,16 @@ Stream::Stream(std::ios& s, FILE* file, Direction direction)
   , FD_(cm_fileno(file))
 {
 #ifdef _WIN32
-  DWORD mode;
   auto h = reinterpret_cast<HANDLE>(_get_osfhandle(this->FD_));
-  if (GetConsoleMode(h, &mode)) {
+  if (GetConsoleMode(h, &this->ConsoleOrigMode_)) {
     this->Console_ = h;
-    DWORD vtMode = mode |
+    DWORD vtMode = this->ConsoleOrigMode_ |
       (direction == Direction::In ? ENABLE_VIRTUAL_TERMINAL_INPUT
                                   : ENABLE_VIRTUAL_TERMINAL_PROCESSING);
     if (SetConsoleMode(this->Console_, vtMode)) {
       this->Kind_ = TermKind::VT100;
     } else {
-      SetConsoleMode(this->Console_, mode);
+      SetConsoleMode(this->Console_, this->ConsoleOrigMode_);
       this->Kind_ = TermKind::Console;
     }
   }
@@ -137,6 +136,18 @@ Stream::Stream(std::ios& s, FILE* file, Direction direction)
 #endif
 }
 
+#ifdef _WIN32
+Stream::~Stream()
+{
+  if (this->Console_) {
+    this->IOS_.rdbuf()->pubsync();
+    SetConsoleMode(this->Console_, this->ConsoleOrigMode_);
+  }
+}
+#else
+Stream::~Stream() = default;
+#endif
+
 IStream::IStream(std::istream& is, FILE* file)
   : Stream(is, file, Direction::In)
 {
diff --git a/Source/cmStdIoStream.h b/Source/cmStdIoStream.h
index c3d28ce8eb..8ff84f93cf 100644
--- a/Source/cmStdIoStream.h
+++ b/Source/cmStdIoStream.h
@@ -53,6 +53,7 @@ protected:
   };
 
   Stream(std::ios& s, FILE* file, Direction direction);
+  ~Stream(); // NOLINT(performance-trivially-destructible)
 
 private:
   std::ios& IOS_;
@@ -61,6 +62,7 @@ private:
 
 #ifdef _WIN32
   void* Console_ = nullptr;
+  unsigned long ConsoleOrigMode_ = 0;
 #endif
 };