From cfc6923c2015a377240fe14cc4ec983227c42912 Mon Sep 17 00:00:00 2001
From: Hleb Valoshka <375gnu@gmail.com>
Date: Sat, 22 Sep 2018 17:34:26 +0300
Subject: [PATCH] Use localtime_r on all platforms to set TZ offset and name
 (Closes: #92)

---
 src/celestia/glutmain.cpp    | 22 ++++++++--------------
 src/celestia/qt/qtappwin.cpp | 16 +++++++---------
 src/celutil/localtime.h      | 24 ++++++++++++++++++++++++
 3 files changed, 39 insertions(+), 23 deletions(-)
 create mode 100644 src/celutil/localtime.h

diff --git a/src/celestia/glutmain.cpp b/src/celestia/glutmain.cpp
index e5371bc02..97e96591e 100644
--- a/src/celestia/glutmain.cpp
+++ b/src/celestia/glutmain.cpp
@@ -29,6 +29,7 @@
 #include <celmath/quaternion.h>
 #include <celutil/util.h>
 #include <celutil/debug.h>
+#include <celutil/localtime.h>
 #include <celmath/mathlib.h>
 #include <celengine/astro.h>
 #include "celestiacore.h"
@@ -517,21 +518,14 @@ int main(int argc, char* argv[])
     appCore->initRenderer();
 
     // Set the simulation starting time to the current system time
-    time_t curtime=time(nullptr);
+    time_t curtime = time(nullptr);
     appCore->start((double) curtime / 86400.0 + (double) astro::Date(1970, 1, 1));
-    #ifdef MACOSX
-    /* localtime in Darwin is is reentrant only
-       equiv to Linux localtime_r()
-       should probably port !MACOSX code to use this too, available since
-       libc 5.2.5 according to manpage */
-    struct tm *temptime=localtime(&curtime);
-    appCore->setTimeZoneBias(temptime->tm_gmtoff);
-    appCore->setTimeZoneName(temptime->tm_zone);
-    #else
-    localtime(&curtime); // Only doing this to set timezone as a side effect
-    appCore->setTimeZoneBias(-timezone);
-    appCore->setTimeZoneName(tzname[daylight?0:1]);
-    #endif
+    struct tm result;
+    if (localtime_r(&curtime, &result))
+    {
+        appCore->setTimeZoneBias(result.tm_gmtoff);
+        appCore->setTimeZoneName(result.tm_zone);
+    }
 
     if (startfile == 1) {
         if (argv[argc - 1][0] == '-') {
diff --git a/src/celestia/qt/qtappwin.cpp b/src/celestia/qt/qtappwin.cpp
index bb0511472..fdfc9bab5 100644
--- a/src/celestia/qt/qtappwin.cpp
+++ b/src/celestia/qt/qtappwin.cpp
@@ -57,11 +57,11 @@
 //#include "qtvideocapturedialog.h"
 #include "celestia/scriptmenu.h"
 #include "celestia/url.h"
+#include "celutil/localtime.h"
 #include "qtbookmark.h"
 
 #if defined(_WIN32)
 #include "celestia/avicapture.h"
-
 // TODO: Add Mac support
 #elif !defined(TARGET_OS_MAC)
 #ifdef THEORA
@@ -1334,15 +1334,13 @@ void CelestiaAppWindow::createMenus()
     // Set up the default time zone name and offset from UTC
     time_t curtime = time(nullptr);
     m_appCore->start(astro::UTCtoTDB((double) curtime / 86400.0 + (double) astro::Date(1970, 1, 1)));
-    localtime(&curtime); // Only doing this to set timezone as a side effect
 
-#ifdef TARGET_OS_MAC
-    CFTimeZoneRef tz = CFTimeZoneCopyDefault();
-    m_appCore->setTimeZoneBias(-CFTimeZoneGetSecondsFromGMT(tz, CFAbsoluteTimeGetCurrent())+3600*daylight);
-    CFRelease(tz);
-#else
-    m_appCore->setTimeZoneBias(-timezone + 3600 * daylight);
-#endif
+    struct tm result;
+    if (localtime_r(&curtime, &result))
+    {
+        m_appCore->setTimeZoneBias(result.tm_gmtoff);
+        m_appCore->setTimeZoneName(result.tm_zone);
+    }
 
     // If LocalTime is set to false, set the time zone bias to zero.
     if (settings.contains("LocalTime"))
diff --git a/src/celutil/localtime.h b/src/celutil/localtime.h
new file mode 100644
index 000000000..e0ccd4bca
--- /dev/null
+++ b/src/celutil/localtime.h
@@ -0,0 +1,24 @@
+#ifndef LOCALTIME_H
+#define LOCALTIME_H
+
+#ifdef _WIN32
+/*
+  Very dump implementation of localtime_r for Windows platform.
+*/
+extern "C" {
+    struct tm *localtime_r(time_t *clock, struct tm *result)
+    {
+        struct tm *p = localtime(clock);
+
+        if (p)
+        {
+            *result = *p;
+            return result;
+        }
+
+        return NULL;
+    }
+}
+#endif
+
+#endif