From 52410813f22def236c7ce28390fbd18cb0b582d4 Mon Sep 17 00:00:00 2001
From: "Admiral H. Curtiss" <pikachu025@gmail.com>
Date: Sun, 18 Feb 2024 04:40:25 +0100
Subject: [PATCH 1/2] Common: Add utility function that wraps localtime_s() or
 localtime_t().

---
 Source/Core/Common/CMakeLists.txt |  2 ++
 Source/Core/Common/TimeUtil.cpp   | 24 ++++++++++++++++++++++++
 Source/Core/Common/TimeUtil.h     | 13 +++++++++++++
 Source/Core/DolphinLib.props      |  2 ++
 4 files changed, 41 insertions(+)
 create mode 100644 Source/Core/Common/TimeUtil.cpp
 create mode 100644 Source/Core/Common/TimeUtil.h

diff --git a/Source/Core/Common/CMakeLists.txt b/Source/Core/Common/CMakeLists.txt
index 61bc9155da..1431239af2 100644
--- a/Source/Core/Common/CMakeLists.txt
+++ b/Source/Core/Common/CMakeLists.txt
@@ -138,6 +138,8 @@ add_library(common
   Thread.h
   Timer.cpp
   Timer.h
+  TimeUtil.cpp
+  TimeUtil.h
   TraversalClient.cpp
   TraversalClient.h
   TraversalProto.h
diff --git a/Source/Core/Common/TimeUtil.cpp b/Source/Core/Common/TimeUtil.cpp
new file mode 100644
index 0000000000..39d989fb3f
--- /dev/null
+++ b/Source/Core/Common/TimeUtil.cpp
@@ -0,0 +1,24 @@
+// Copyright 2024 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "Common/TimeUtil.h"
+
+#include <ctime>
+#include <optional>
+
+namespace Common
+{
+std::optional<std::tm> Localtime(std::time_t time)
+{
+  std::tm local_time;
+#ifdef _MSC_VER
+  if (localtime_s(&local_time, &time) != 0)
+    return std::nullopt;
+#else
+  std::tm* result = localtime_r(&time, &local_time);
+  if (result != &local_time)
+    return std::nullopt;
+#endif
+  return local_time;
+}
+}  // Namespace Common
diff --git a/Source/Core/Common/TimeUtil.h b/Source/Core/Common/TimeUtil.h
new file mode 100644
index 0000000000..ff9ca02a12
--- /dev/null
+++ b/Source/Core/Common/TimeUtil.h
@@ -0,0 +1,13 @@
+// Copyright 2024 Dolphin Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <ctime>
+#include <optional>
+
+namespace Common
+{
+// Threadsafe and error-checking variant of std::localtime()
+std::optional<std::tm> Localtime(std::time_t time);
+}  // Namespace Common
diff --git a/Source/Core/DolphinLib.props b/Source/Core/DolphinLib.props
index 74b3185753..42ae7ba5e6 100644
--- a/Source/Core/DolphinLib.props
+++ b/Source/Core/DolphinLib.props
@@ -161,6 +161,7 @@
     <ClInclude Include="Common\SymbolDB.h" />
     <ClInclude Include="Common\Thread.h" />
     <ClInclude Include="Common\Timer.h" />
+    <ClInclude Include="Common\TimeUtil.h" />
     <ClInclude Include="Common\TraversalClient.h" />
     <ClInclude Include="Common\TraversalProto.h" />
     <ClInclude Include="Common\TypeUtils.h" />
@@ -832,6 +833,7 @@
     <ClCompile Include="Common\SymbolDB.cpp" />
     <ClCompile Include="Common\Thread.cpp" />
     <ClCompile Include="Common\Timer.cpp" />
+    <ClCompile Include="Common\TimeUtil.cpp" />
     <ClCompile Include="Common\TraversalClient.cpp" />
     <ClCompile Include="Common\UPnP.cpp" />
     <ClCompile Include="Common\WindowsRegistry.cpp" />

From d3140e72c3f59f203c6c85049c5bcd25f9b14f3b Mon Sep 17 00:00:00 2001
From: "Admiral H. Curtiss" <pikachu025@gmail.com>
Date: Sun, 18 Feb 2024 04:45:37 +0100
Subject: [PATCH 2/2] Core: Fix crash when inspecting a savestate with a
 timestamp that causes localtime() to error out.

---
 Source/Core/Core/State.cpp | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/Source/Core/Core/State.cpp b/Source/Core/Core/State.cpp
index e3e9a441c2..d60747deeb 100644
--- a/Source/Core/Core/State.cpp
+++ b/Source/Core/Core/State.cpp
@@ -29,6 +29,7 @@
 #include "Common/IOFile.h"
 #include "Common/MsgHandler.h"
 #include "Common/Thread.h"
+#include "Common/TimeUtil.h"
 #include "Common/Timer.h"
 #include "Common/Version.h"
 #include "Common/WorkQueueThread.h"
@@ -282,10 +283,12 @@ static std::string SystemTimeAsDoubleToString(double time)
 {
   // revert adjustments from GetSystemTimeAsDouble() to get a normal Unix timestamp again
   const time_t seconds = static_cast<time_t>(time) + DOUBLE_TIME_OFFSET;
-  const tm local_time = fmt::localtime(seconds);
+  const auto local_time = Common::Localtime(seconds);
+  if (!local_time)
+    return "";
 
   // fmt is locale agnostic by default, so explicitly use current locale.
-  return fmt::format(std::locale{""}, "{:%x %X}", local_time);
+  return fmt::format(std::locale{""}, "{:%x %X}", *local_time);
 }
 
 static std::string MakeStateFilename(int number);