5 files changed, 68 insertions, 54 deletions
diff --git a/absl/time/internal/cctz/include/cctz/civil_time.h b/absl/time/internal/cctz/include/cctz/civil_time.h
index f844182b..aa578ee3 100644
--- a/absl/time/internal/cctz/include/cctz/civil_time.h
+++ b/absl/time/internal/cctz/include/cctz/civil_time.h
@@ -306,9 +306,9 @@ using detail::get_weekday;
 //
 //   civil_day d = ...
 //   // Gets the following Thursday if d is not already Thursday
-//   civil_day thurs1 = prev_weekday(d, weekday::thursday) + 7;
+//   civil_day thurs1 = next_weekday(d - 1, weekday::thursday);
 //   // Gets the previous Thursday if d is not already Thursday
-//   civil_day thurs2 = next_weekday(d, weekday::thursday) - 7;
+//   civil_day thurs2 = prev_weekday(d + 1, weekday::thursday);
 //
 using detail::next_weekday;
 using detail::prev_weekday;
diff --git a/absl/time/internal/cctz/src/civil_time_test.cc b/absl/time/internal/cctz/src/civil_time_test.cc
index dc7e5a1d..b1f46f12 100644
--- a/absl/time/internal/cctz/src/civil_time_test.cc
+++ b/absl/time/internal/cctz/src/civil_time_test.cc
@@ -1035,7 +1035,7 @@ TEST(CivilTime, LeapYears) {
 
 TEST(CivilTime, FirstThursdayInMonth) {
   const civil_day nov1(2014, 11, 1);
-  const civil_day thursday = prev_weekday(nov1, weekday::thursday) + 7;
+  const civil_day thursday = next_weekday(nov1 - 1, weekday::thursday);
   EXPECT_EQ("2014-11-06", Format(thursday));
 
   // Bonus: Date of Thanksgiving in the United States
diff --git a/absl/time/internal/cctz/src/time_zone_info.cc b/absl/time/internal/cctz/src/time_zone_info.cc
index 50f7de54..184bd434 100644
--- a/absl/time/internal/cctz/src/time_zone_info.cc
+++ b/absl/time/internal/cctz/src/time_zone_info.cc
@@ -682,7 +682,6 @@ std::unique_ptr<ZoneInfoSource> AndroidZoneInfoSource::Open(
   // Use of the "file:" prefix is intended for testing purposes only.
   if (name.compare(0, 5, "file:") == 0) return Open(name.substr(5));
 
-#if defined(__ANDROID__)
   // See Android's libc/tzcode/bionic.cpp for additional information.
   for (const char* tzdata : {"/data/misc/zoneinfo/current/tzdata",
                              "/system/usr/share/zoneinfo/tzdata"}) {
@@ -717,7 +716,7 @@ std::unique_ptr<ZoneInfoSource> AndroidZoneInfoSource::Open(
       }
     }
   }
-#endif  // __ANDROID__
+
   return nullptr;
 }
 
diff --git a/absl/time/internal/cctz/src/time_zone_libc.cc b/absl/time/internal/cctz/src/time_zone_libc.cc
index 3ab1623c..6095e764 100644
--- a/absl/time/internal/cctz/src/time_zone_libc.cc
+++ b/absl/time/internal/cctz/src/time_zone_libc.cc
@@ -21,7 +21,6 @@
 #include <chrono>
 #include <ctime>
 #include <limits>
-#include <tuple>
 #include <utility>
 
 #include "absl/time/internal/cctz/include/cctz/civil_time.h"
@@ -33,57 +32,75 @@ namespace cctz {
 
 namespace {
 
-// .first is seconds east of UTC; .second is the time-zone abbreviation.
-using OffsetAbbr = std::pair<int, const char*>;
-
-// Defines a function that can be called as follows:
-//
-//   std::tm tm = ...;
-//   OffsetAbbr off_abbr = get_offset_abbr(tm);
-//
 #if defined(_WIN32) || defined(_WIN64)
 // Uses the globals: '_timezone', '_dstbias' and '_tzname'.
-OffsetAbbr get_offset_abbr(const std::tm& tm) {
+auto tm_gmtoff(const std::tm& tm) -> decltype(_timezone + _dstbias) {
   const bool is_dst = tm.tm_isdst > 0;
-  const int off = _timezone + (is_dst ? _dstbias : 0);
-  const char* abbr = _tzname[is_dst];
-  return {off, abbr};
+  return _timezone + (is_dst ? _dstbias : 0);
+}
+auto tm_zone(const std::tm& tm) -> decltype(_tzname[0]) {
+  const bool is_dst = tm.tm_isdst > 0;
+  return _tzname[is_dst];
 }
 #elif defined(__sun)
 // Uses the globals: 'timezone', 'altzone' and 'tzname'.
-OffsetAbbr get_offset_abbr(const std::tm& tm) {
+auto tm_gmtoff(const std::tm& tm) -> decltype(timezone) {
   const bool is_dst = tm.tm_isdst > 0;
-  const int off = is_dst ? altzone : timezone;
-  const char* abbr = tzname[is_dst];
-  return {off, abbr};
+  return is_dst ? altzone : timezone;
+}
+auto tm_zone(const std::tm& tm) -> decltype(tzname[0]) {
+  const bool is_dst = tm.tm_isdst > 0;
+  return tzname[is_dst];
 }
 #elif defined(__native_client__) || defined(__myriad2__) || \
     defined(__EMSCRIPTEN__)
 // Uses the globals: 'timezone' and 'tzname'.
-OffsetAbbr get_offset_abbr(const std::tm& tm) {
+auto tm_gmtoff(const std::tm& tm) -> decltype(_timezone + 0) {
+  const bool is_dst = tm.tm_isdst > 0;
+  return _timezone + (is_dst ? 60 * 60 : 0);
+}
+auto tm_zone(const std::tm& tm) -> decltype(tzname[0]) {
   const bool is_dst = tm.tm_isdst > 0;
-  const int off = _timezone + (is_dst ? 60 * 60 : 0);
-  const char* abbr = tzname[is_dst];
-  return {off, abbr};
+  return tzname[is_dst];
+}
+#else
+// Adapt to different spellings of the struct std::tm extension fields.
+#if defined(tm_gmtoff)
+auto tm_gmtoff(const std::tm& tm) -> decltype(tm.tm_gmtoff) {
+  return tm.tm_gmtoff;
+}
+#elif defined(__tm_gmtoff)
+auto tm_gmtoff(const std::tm& tm) -> decltype(tm.__tm_gmtoff) {
+  return tm.__tm_gmtoff;
+}
+#else
+template <typename T>
+auto tm_gmtoff(const T& tm) -> decltype(tm.tm_gmtoff) {
+  return tm.tm_gmtoff;
+}
+template <typename T>
+auto tm_gmtoff(const T& tm) -> decltype(tm.__tm_gmtoff) {
+  return tm.__tm_gmtoff;
+}
+#endif  // tm_gmtoff
+#if defined(tm_zone)
+auto tm_zone(const std::tm& tm) -> decltype(tm.tm_zone) {
+  return tm.tm_zone;
+}
+#elif defined(__tm_zone)
+auto tm_zone(const std::tm& tm) -> decltype(tm.__tm_zone) {
+  return tm.__tm_zone;
 }
 #else
-//
-// Returns an OffsetAbbr using std::tm fields with various spellings.
-//
-#if !defined(tm_gmtoff) && !defined(tm_zone)
 template <typename T>
-OffsetAbbr get_offset_abbr(const T& tm, decltype(&T::tm_gmtoff) = nullptr,
-                           decltype(&T::tm_zone) = nullptr) {
-  return {tm.tm_gmtoff, tm.tm_zone};
+auto tm_zone(const T& tm) -> decltype(tm.tm_zone) {
+  return tm.tm_zone;
 }
-#endif  // !defined(tm_gmtoff) && !defined(tm_zone)
-#if !defined(__tm_gmtoff) && !defined(__tm_zone)
 template <typename T>
-OffsetAbbr get_offset_abbr(const T& tm, decltype(&T::__tm_gmtoff) = nullptr,
-                           decltype(&T::__tm_zone) = nullptr) {
-  return {tm.__tm_gmtoff, tm.__tm_zone};
+auto tm_zone(const T& tm) -> decltype(tm.__tm_zone) {
+  return tm.__tm_zone;
 }
-#endif  // !defined(__tm_gmtoff) && !defined(__tm_zone)
+#endif  // tm_zone
 #endif
 
 inline std::tm* gm_time(const std::time_t *timep, std::tm *result) {
@@ -126,7 +143,7 @@ bool make_time(const civil_second& cs, int is_dst, std::time_t* t, int* off) {
       return false;
     }
   }
-  *off = get_offset_abbr(tm).first;
+  *off = static_cast<int>(tm_gmtoff(tm));
   return true;
 }
 
@@ -137,7 +154,7 @@ std::time_t find_trans(std::time_t lo, std::time_t hi, int offset) {
   while (lo + 1 != hi) {
     const std::time_t mid = lo + (hi - lo) / 2;
     if (std::tm* tmp = local_time(&mid, &tm)) {
-      if (get_offset_abbr(*tmp).first == offset) {
+      if (tm_gmtoff(*tmp) == offset) {
         hi = mid;
       } else {
         lo = mid;
@@ -147,7 +164,7 @@ std::time_t find_trans(std::time_t lo, std::time_t hi, int offset) {
       // ignoring all failed conversions.  Slow, but never really happens.
       while (++lo != hi) {
         if (std::tm* tmp = local_time(&lo, &tm)) {
-          if (get_offset_abbr(*tmp).first == offset) break;
+          if (tm_gmtoff(*tmp) == offset) break;
         }
       }
       return lo;
@@ -193,8 +210,8 @@ time_zone::absolute_lookup TimeZoneLibC::BreakTime(
   const year_t year = tmp->tm_year + year_t{1900};
   al.cs = civil_second(year, tmp->tm_mon + 1, tmp->tm_mday,
                        tmp->tm_hour, tmp->tm_min, tmp->tm_sec);
-  std::tie(al.offset, al.abbr) = get_offset_abbr(*tmp);
-  if (!local_) al.abbr = "UTC";  // as expected by cctz
+  al.offset = static_cast<int>(tm_gmtoff(*tmp));
+  al.abbr = local_ ? tm_zone(*tmp) : "UTC";  // as expected by cctz
   al.is_dst = tmp->tm_isdst > 0;
   return al;
 }
diff --git a/absl/time/internal/cctz/src/zone_info_source.cc b/absl/time/internal/cctz/src/zone_info_source.cc
index 13248462..42f50c5e 100644
--- a/absl/time/internal/cctz/src/zone_info_source.cc
+++ b/absl/time/internal/cctz/src/zone_info_source.cc
@@ -46,7 +46,13 @@ std::unique_ptr<absl::time_internal::cctz::ZoneInfoSource> DefaultFactory(
 // A "weak" definition for cctz_extension::zone_info_source_factory.
 // The user may override this with their own "strong" definition (see
 // zone_info_source.h).
-#if defined(_MSC_VER)
+#if !defined(__has_attribute)
+#define __has_attribute(x) 0
+#endif
+#if __has_attribute(weak) || defined(__GNUC__)
+ZoneInfoSourceFactory zone_info_source_factory
+    __attribute__((weak)) = DefaultFactory;
+#elif defined(_MSC_VER) && !defined(_LIBCPP_VERSION)
 extern ZoneInfoSourceFactory zone_info_source_factory;
 extern ZoneInfoSourceFactory default_factory;
 ZoneInfoSourceFactory default_factory = DefaultFactory;
@@ -60,19 +66,11 @@ ZoneInfoSourceFactory default_factory = DefaultFactory;
     "/alternatename:?zone_info_source_factory@cctz_extension@time_internal@absl@@3P6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@absl@@U?$default_delete@VZoneInfoSource@cctz@time_internal@absl@@@std@@@std@@AEBV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@5@AEBV?$function@$$A6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@absl@@U?$default_delete@VZoneInfoSource@cctz@time_internal@absl@@@std@@@std@@AEBV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@2@@Z@5@@ZEA=?default_factory@cctz_extension@time_internal@absl@@3P6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@absl@@U?$default_delete@VZoneInfoSource@cctz@time_internal@absl@@@std@@@std@@AEBV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@5@AEBV?$function@$$A6A?AV?$unique_ptr@VZoneInfoSource@cctz@time_internal@absl@@U?$default_delete@VZoneInfoSource@cctz@time_internal@absl@@@std@@@std@@AEBV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@2@@Z@5@@ZEA")
 #else
 #error Unsupported MSVC platform
-#endif
-#else  // _MSC_VER
-#if !defined(__has_attribute)
-#define __has_attribute(x) 0
-#endif
-#if __has_attribute(weak) || defined(__GNUC__)
-ZoneInfoSourceFactory zone_info_source_factory
-    __attribute__((weak)) = DefaultFactory;
+#endif  // _M_<PLATFORM>
 #else
 // Make it a "strong" definition if we have no other choice.
 ZoneInfoSourceFactory zone_info_source_factory = DefaultFactory;
 #endif
-#endif  // _MSC_VER
 
 }  // namespace cctz_extension
 }  // namespace time_internal