From 6aff466066a9985a596df7ce5c5b19c8784d85c8 Mon Sep 17 00:00:00 2001
From: Leonard Hecker <lhecker@microsoft.com>
Date: Sat, 2 Dec 2023 15:39:04 +0100
Subject: [PATCH] Fix a coroutine AV crash

---
 src/cascadia/TerminalApp/TerminalTab.cpp | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/src/cascadia/TerminalApp/TerminalTab.cpp b/src/cascadia/TerminalApp/TerminalTab.cpp
index c363ec1d9f9..06121ab945d 100644
--- a/src/cascadia/TerminalApp/TerminalTab.cpp
+++ b/src/cascadia/TerminalApp/TerminalTab.cpp
@@ -933,9 +933,13 @@ namespace winrt::TerminalApp::implementation
         ControlEventTokens events{};
 
         events.titleToken = control.TitleChanged([dispatcher, weakThis](auto&&, auto&&) -> winrt::fire_and_forget {
+            // The lambda lives in the `std::function`-style container owned by `control`. That is, when the
+            // `control` gets destroyed the lambda struct also gets destroyed. In other words, we need to
+            // copy `weakThis` onto the stack, because that's the only thing that gets captured in coroutines.
+            // See: https://devblogs.microsoft.com/oldnewthing/20211103-00/?p=105870
+            const auto weakThisCopy = weakThis;
             co_await wil::resume_foreground(dispatcher);
-            // Check if Tab's lifetime has expired
-            if (auto tab{ weakThis.get() })
+            if (auto tab{ weakThisCopy.get() })
             {
                 // The title of the control changed, but not necessarily the title of the tab.
                 // Set the tab's text to the active panes' text.
@@ -944,8 +948,9 @@ namespace winrt::TerminalApp::implementation
         });
 
         events.colorToken = control.TabColorChanged([dispatcher, weakThis](auto&&, auto&&) -> winrt::fire_and_forget {
+            const auto weakThisCopy = weakThis;
             co_await wil::resume_foreground(dispatcher);
-            if (auto tab{ weakThis.get() })
+            if (auto tab{ weakThisCopy.get() })
             {
                 // The control's tabColor changed, but it is not necessarily the
                 // active control in this tab. We'll just recalculate the
@@ -955,33 +960,36 @@ namespace winrt::TerminalApp::implementation
         });
 
         events.taskbarToken = control.SetTaskbarProgress([dispatcher, weakThis](auto&&, auto&&) -> winrt::fire_and_forget {
+            const auto weakThisCopy = weakThis;
             co_await wil::resume_foreground(dispatcher);
-            // Check if Tab's lifetime has expired
-            if (auto tab{ weakThis.get() })
+            if (auto tab{ weakThisCopy.get() })
             {
                 tab->_UpdateProgressState();
             }
         });
 
         events.stateToken = control.ConnectionStateChanged([dispatcher, weakThis](auto&&, auto&&) -> winrt::fire_and_forget {
+            const auto weakThisCopy = weakThis;
             co_await wil::resume_foreground(dispatcher);
-            if (auto tab{ weakThis.get() })
+            if (auto tab{ weakThisCopy.get() })
             {
                 tab->_UpdateConnectionClosedState();
             }
         });
 
         events.readOnlyToken = control.ReadOnlyChanged([dispatcher, weakThis](auto&&, auto&&) -> winrt::fire_and_forget {
+            const auto weakThisCopy = weakThis;
             co_await wil::resume_foreground(dispatcher);
-            if (auto tab{ weakThis.get() })
+            if (auto tab{ weakThisCopy.get() })
             {
                 tab->_RecalculateAndApplyReadOnly();
             }
         });
 
         events.focusToken = control.FocusFollowMouseRequested([dispatcher, weakThis](auto sender, auto) -> winrt::fire_and_forget {
+            const auto weakThisCopy = weakThis;
             co_await wil::resume_foreground(dispatcher);
-            if (const auto tab{ weakThis.get() })
+            if (const auto tab{ weakThisCopy.get() })
             {
                 if (tab->_focused())
                 {