time/Convert: fallback TimeGm() implementation

src/time/Convert.cxx

@@ -67,15 +67,42 @@ LocalTime(std::chrono::system_clock::time_point tp)
 	return *tm;
 }
 
-#ifdef __GLIBC__
+#ifndef __GLIBC__
+
+/**
+ * Determine the time zone offset in a portable way.
+ */
+gcc_const
+static time_t
+GetTimeZoneOffset() noexcept
+{
+	time_t t = 1234567890;
+	struct tm tm;
+	tm.tm_isdst = 0;
+#ifdef _WIN32
+	struct tm *p = gmtime(&t);
+#else
+	struct tm *p = &tm;
+	gmtime_r(&t, p);
+#endif
+	return t - mktime(&tm);
+}
+
+#endif /* !__GLIBC__ */
 
 std::chrono::system_clock::time_point
 TimeGm(struct tm &tm) noexcept
 {
-	return std::chrono::system_clock::from_time_t(timegm(&tm));
-}
+#ifdef __GLIBC__
+	/* timegm() is a GNU extension */
+	const auto t = timegm(&tm);
+#else
+	tm.tm_isdst = 0;
+	const auto t = mktime(&tm) + GetTimeZoneOffset();
+#endif /* !__GLIBC__ */
 
-#endif
+	return std::chrono::system_clock::from_time_t(t);
+}
 
 std::chrono::system_clock::time_point
 MakeTime(struct tm &tm) noexcept

src/time/Convert.hxx

@@ -53,8 +53,6 @@ GmTime(std::chrono::system_clock::time_point tp);
 struct tm
 LocalTime(std::chrono::system_clock::time_point tp);
 
-#ifdef __GLIBC__
-
 /**
  * Convert a UTC-based "struct tm" to a UTC-based time point.
  */
@@ -62,8 +60,6 @@ gcc_pure
 std::chrono::system_clock::time_point
 TimeGm(struct tm &tm) noexcept;
 
-#endif
-
 /**
  * Convert a local "struct tm" to a UTC-based time point.
  */

src/time/Parser.cxx

 /*
- * Copyright (C) 2014-2017 Max Kellermann <max.kellermann@gmail.com>
+ * Copyright 2014-2019 Max Kellermann <max.kellermann@gmail.com>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -29,31 +29,12 @@
 
 #include "Parser.hxx"
 #include "Convert.hxx"
-#include "util/Compiler.h"
 
 #include <stdexcept>
 
 #include <assert.h>
 #include <time.h>
 
-#if !defined(__GLIBC__) && !defined(_WIN32)
-
-/**
- * Determine the time zone offset in a portable way.
- */
-gcc_const
-static time_t
-GetTimeZoneOffset() noexcept
-{
-	time_t t = 1234567890;
-	struct tm tm;
-	tm.tm_isdst = 0;
-	gmtime_r(&t, &tm);
-	return t - mktime(&tm);
-}
-
-#endif
-
 std::chrono::system_clock::time_point
 ParseTimePoint(const char *s, const char *format)
 {
@@ -71,13 +52,6 @@ ParseTimePoint(const char *s, const char *format)
 	if (end == nullptr || *end != 0)
 		throw std::runtime_error("Failed to parse time stamp");
 
-#ifdef __GLIBC__
-	/* timegm() is a GNU extension */
 	return TimeGm(tm);
-#else
-	tm.tm_isdst = 0;
-	const auto t = mktime(&tm) + GetTimeZoneOffset();
-	return std::chrono::system_clock::from_time_t(t);
-#endif /* !__GLIBC__ */
 #endif /* !_WIN32 */
 }

src/time/Parser.hxx

 /*
- * Copyright (C) 2014-2017 Max Kellermann <max.kellermann@gmail.com>
+ * Copyright 2014-2019 Max Kellermann <max.kellermann@gmail.com>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions