[winpr,timezone] unify TZ override and restore

winpr/libwinpr/timezone/CMakeLists.txt

@@ -30,7 +30,7 @@ if(WITH_TIMEZONE_FROM_FILE)
   install(FILES TimeZoneNameMap.json DESTINATION ${WINPR_RESOURCE_ROOT})
 endif()
 
-set(SRCS TimeZoneNameMapUtils.c TimeZoneNameMap.h timezone.c)
+set(SRCS TimeZoneNameMapUtils.c TimeZoneNameMap.h timezone.c timezone.h)
 if(WITH_TIMEZONE_COMPILED)
   list(APPEND SRCS TimeZoneNameMap_static.h)
 endif()

winpr/libwinpr/timezone/TimeZoneIanaAbbrevMap.c

@@ -27,6 +27,7 @@
 #include <unistd.h>
 
 #include <winpr/string.h>
+#include "timezone.h"
 
 typedef struct
 {
@@ -73,25 +74,14 @@ static void append_timezone(const char* dir, const char* name)
 	if (!tz)
 		return;
 
-	const char* otz = getenv("TZ");
-	char* oldtz = NULL;
-	if (otz)
-		oldtz = _strdup(otz);
-	setenv("TZ", tz, 1);
-	tzset();
+	char* oldtz = setNewAndSaveOldTZ(tz);
+
 	const time_t t = time(NULL);
 	struct tm lt = { 0 };
 	(void)localtime_r(&t, &lt);
 	append(tz, lt.tm_zone);
-	if (oldtz)
-	{
-		setenv("TZ", oldtz, 1);
-		free(oldtz);
-	}
-	else
-		unsetenv("TZ");
+	restoreSavedTZ(oldtz);
 	free(tz);
-	tzset();
 }
 
 static void handle_link(const char* base, const char* dir, const char* name);

winpr/libwinpr/timezone/timezone.c

@@ -28,6 +28,7 @@
 #include <winpr/assert.h>
 #include <winpr/file.h>
 #include "../log.h"
+#include "timezone.h"
 
 #define TAG WINPR_TAG("timezone")
 
@@ -875,31 +876,12 @@ DWORD EnumDynamicTimeZoneInformation(const DWORD dwIndex,
 	const time_t t = time(NULL);
 	struct tm tres = { 0 };
 
-	const char* tz = getenv("TZ");
-	char* tzcopy = NULL;
-	if (tz)
-	{
-		size_t tzianalen = 0;
-		winpr_asprintf(&tzcopy, &tzianalen, "TZ=%s", tz);
-	}
+	char* tzcopy = entry->Iana ? setNewAndSaveOldTZ(entry->Iana) : NULL;
 
-	char* tziana = NULL;
-	{
-		size_t tzianalen = 0;
-		winpr_asprintf(&tziana, &tzianalen, "TZ=%s", entry->Iana);
-	}
-	if (tziana)
-		putenv(tziana);
-
-	tzset();
 	struct tm* local_time = localtime_r(&t, &tres);
-	free(tziana);
-	if (tzcopy)
-		putenv(tzcopy);
-	else
-		unsetenv("TZ");
-	free(tzcopy);
-	tzset();
+
+	if (entry->Iana)
+		restoreSavedTZ(tzcopy);
 
 	if (local_time)
 		dynamic_time_zone_from_localtime(local_time, lpTimeZoneInformation);
@@ -936,3 +918,32 @@ DWORD GetDynamicTimeZoneInformationEffectiveYears(
 	return ERROR_FILE_NOT_FOUND;
 }
 #endif
+
+#if !defined(_WIN32)
+char* setNewAndSaveOldTZ(const char* val)
+{
+	// NOLINTBEGIN(concurrency-mt-unsafe)
+	const char* otz = getenv("TZ");
+	char* oldtz = NULL;
+	if (otz)
+		oldtz = _strdup(otz);
+	setenv("TZ", val, 1);
+	tzset();
+	// NOLINTEND(concurrency-mt-unsafe)
+	return oldtz;
+}
+
+void restoreSavedTZ(char* saved)
+{
+	// NOLINTBEGIN(concurrency-mt-unsafe)
+	if (saved)
+	{
+		setenv("TZ", saved, 1);
+		free(saved);
+	}
+	else
+		unsetenv("TZ");
+	tzset();
+	// NOLINTEND(concurrency-mt-unsafe)
+}
+#endif

winpr/libwinpr/timezone/timezone.h

@@ -0,0 +1,26 @@
+/**
+ * WinPR: Windows Portable Runtime
+ * Time Zone
+ *
+ * Copyright 2025 Armin Novak <anovak@thincast.com>
+ * Copyright 2025 Thincast Technologies GmbH
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#if !defined(_WIN32)
+char* setNewAndSaveOldTZ(const char* val);
+void restoreSavedTZ(char* saved);
+#endif