leap_second_info
get_leap_second_info(const utc_time<_Duration>& __ut);
+ /// @cond undocumented
+ namespace __detail
+ {
+ bool __recent_leap_second_info(leap_second_info&, unsigned);
+ }
+ /// @endcond
+
/** A clock that measures Universal Coordinated Time (UTC).
*
* The epoch is 1970-01-01 00:00:00.
friend class leap_second;
friend struct time_zone::_Impl;
friend class time_zone_link;
+
+ friend bool
+ __detail::__recent_leap_second_info(leap_second_info&, unsigned);
};
class time_zone_link
{ return __x.date() <=> __y; }
private:
- explicit leap_second(seconds::rep __s) : _M_s(__s) { }
+ constexpr explicit leap_second(seconds::rep __s) : _M_s(__s) { }
friend struct tzdb_list::_Node;
friend const tzdb& reload_tzdb();
- template<typename _Duration>
- friend leap_second_info
- get_leap_second_info(const utc_time<_Duration>&);
-
seconds _M_s; // == date().time_since_epoch() * value().count()
};
namespace __detail
{
+ // This function is inline to support fast conversions between utc_time
+ // and sys_time when possible, without requiring a chrono::tzdb object
+ // to be constructed.
inline leap_second_info
__get_leap_second_info(sys_seconds __ss, bool __is_utc)
{
1435708800, // 1 Jul 2015
1483228800, // 1 Jan 2017
};
+
+ // The default result for times after the last leap year.
+ constexpr leap_second_info __after_last{
+ .is_leap_second = false,
+ .elapsed = seconds(std::size(__leaps))
+ };
+
// The list above is known to be valid until (at least) this date
// and only contains positive leap seconds.
constexpr sys_seconds __expires(1798416000s); // 2026-12-28 00:00:00 UTC
-#if _GLIBCXX_USE_CXX11_ABI || ! _GLIBCXX_USE_DUAL_ABI
if (__ss > __expires)
{
- // Use updated leap_seconds from tzdb.
- size_t __n = std::size(__leaps);
-
- auto __db = get_tzdb_list().begin();
- auto __first = __db->leap_seconds.begin() + __n;
- auto __last = __db->leap_seconds.end();
- auto __pos = std::upper_bound(__first, __last, __ss);
- seconds __elapsed(__n);
- for (auto __i = __first; __i != __pos; ++__i)
- __elapsed += __i->value();
-
- if (__is_utc)
- {
- // Convert utc_time to sys_time:
- __ss -= __elapsed;
- // See if that sys_time is before (or during) previous leap sec:
- if (__pos != __first && __ss < __pos[-1])
- {
- if ((__ss + 1s) >= __pos[-1])
- return {true, __elapsed};
- __elapsed -= __pos[-1].value();
- }
- }
- return {false, __elapsed};
- }
- else
+#if _GLIBCXX_USE_CXX11_ABI || ! _GLIBCXX_USE_DUAL_ABI // use chrono::tzdb
+ // Call into the library because it might have knowledge of new
+ // leap seconds loaded at runtime from the tzdata files.
+
+ // We misuse leap_second_info here to pass {bool, seconds} inputs:
+ leap_second_info __info{ .is_leap_second = __is_utc,
+ .elapsed = __ss.time_since_epoch() };
+ // If this returns true, then __info holds the output result:
+ if (__detail::__recent_leap_second_info(__info, std::size(__leaps)))
+ return __info;
#endif
- {
- seconds::rep __s = __ss.time_since_epoch().count();
- const seconds::rep* __first = std::begin(__leaps);
- const seconds::rep* __last = std::end(__leaps);
+ return __after_last;
+ }
- // Don't bother searching the list if we're after the last one.
- if (__s > (__last[-1] + (__last - __first) + 1))
- return { false, seconds(__last - __first) };
+ seconds::rep __s = __ss.time_since_epoch().count();
+ const seconds::rep* __first = std::begin(__leaps);
+ const seconds::rep* __last = std::end(__leaps);
- auto __pos = std::upper_bound(__first, __last, __s);
- seconds __elapsed{__pos - __first};
- if (__is_utc)
+ // Don't bother searching the list if we're after the last one.
+ if (__s > (__last[-1] + (__last - __first) + 1))
+ return __after_last;
+
+ auto __pos = std::upper_bound(__first, __last, __s);
+ seconds __elapsed{__pos - __first};
+ if (__is_utc)
+ {
+ // Convert utc_time to sys_time:
+ __s -= __elapsed.count();
+ // See if that sys_time is before (or during) previous leap sec:
+ if (__pos != __first && __s < __pos[-1])
{
- // Convert utc_time to sys_time:
- __s -= __elapsed.count();
- // See if that sys_time is before (or during) previous leap sec:
- if (__pos != __first && __s < __pos[-1])
- {
- if ((__s + 1) >= __pos[-1])
- return {true, __elapsed};
- --__elapsed;
- }
+ if ((__s + 1) >= __pos[-1])
+ return {true, __elapsed};
+ --__elapsed;
}
- return {false, __elapsed};
}
+ return {false, __elapsed};
}
} // namespace __detail
#include <memory> // atomic<shared_ptr<T>>
#include <mutex> // mutex
#include <iomanip> // quoted
+#include <span>
#if defined __GTHREADS && ! defined _GLIBCXX_HAS_GTHREADS
# include <ext/concurrence.h> // __gnu_cxx::__mutex
#endif
static const tzdb& _S_replace_head(shared_ptr<_Node>, shared_ptr<_Node>);
static pair<vector<leap_second>, bool> _S_read_leap_seconds();
+
+ // This is here because _Node is a friend so can call private constructor.
+ static const leap_second fixed_leaps[];
};
// Implementation of the private constructor used for the singleton object.
}
#endif // TZDB_DISABLED
+// These are the same values as the array in the <chrono> header, but might
+// contain additional leap seconds if the libstdc++.so used at runtime is
+// newer than the <chrono> header used to compile parts of the application.
+constexpr leap_second tzdb_list::_Node::fixed_leaps[] {
+#define LS leap_second
+ LS( 78796800), // 1 Jul 1972
+ LS( 94694400), // 1 Jan 1973
+ LS( 126230400), // 1 Jan 1974
+ LS( 157766400), // 1 Jan 1975
+ LS( 189302400), // 1 Jan 1976
+ LS( 220924800), // 1 Jan 1977
+ LS( 252460800), // 1 Jan 1978
+ LS( 283996800), // 1 Jan 1979
+ LS( 315532800), // 1 Jan 1980
+ LS( 362793600), // 1 Jul 1981
+ LS( 394329600), // 1 Jul 1982
+ LS( 425865600), // 1 Jul 1983
+ LS( 489024000), // 1 Jul 1985
+ LS( 567993600), // 1 Jan 1988
+ LS( 631152000), // 1 Jan 1990
+ LS( 662688000), // 1 Jan 1991
+ LS( 709948800), // 1 Jul 1992
+ LS( 741484800), // 1 Jul 1993
+ LS( 773020800), // 1 Jul 1994
+ LS( 820454400), // 1 Jan 1996
+ LS( 867715200), // 1 Jul 1997
+ LS( 915148800), // 1 Jan 1999
+ LS(1136073600), // 1 Jan 2006
+ LS(1230768000), // 1 Jan 2009
+ LS(1341100800), // 1 Jul 2012
+ LS(1435708800), // 1 Jul 2015
+ LS(1483228800), // 1 Jan 2017
+ // If new leap seconds get defined they should be added here.
+ // Negative leap seconds are represented as -1 * timestamp.
+#undef LS
+};
+
+namespace
+{
+ // The expiry date corresponding to the list above.
+ // tzdata 2026a leapseconds list expires at 2026-12-28 00:00:00 UTC
+ constexpr seconds fixed_expiry{1798416000u};
+
+ // This holds the most up-to-date number of leap seconds known at runtime.
+ // Initially zero, updated when _S_read_leap_seconds() is called.
+ constinit atomic<unsigned> num_leap_seconds{0};
+}
+
+ namespace __detail
+ {
+ // Called by chrono::__detail::__get_leap_second_info in <chrono>
+ // to get leap_second_info for times after the expiry date in the header.
+ // The caller provides the time being queried in `info.elapsed` and
+ // whether that is a UTC time in `info.is_leap_second`.
+ // If it returns true, this function did the lookup and updated `info`.
+ // If this returns false, it means the hardcoded list of leap seconds
+ // in the header should be used for the lookup.
+ bool
+ __recent_leap_second_info(leap_second_info& info,
+ unsigned num_positive_leaps)
+ {
+ // Extract the input args from info:
+ const auto [is_utc, secs] = info;
+ // And then reuse info for the output result:
+ info.is_leap_second = false;
+ info.elapsed = seconds(num_positive_leaps);
+
+ auto update_info = [&](span<const leap_second> leaps)
+ {
+ if (leaps.size() == num_positive_leaps)
+ return false; // No new leap seconds, use the array in the header.
+
+ // info.elapsed already contains the first N leap seconds,
+ // so we only search the end of the span.
+ auto first = leaps.begin() + num_positive_leaps;
+ auto pos = std::upper_bound(first, leaps.end(), sys_seconds(secs));
+ for (auto i = first; i != pos; ++i)
+ info.elapsed += i->value();
+
+ if (is_utc)
+ {
+ // This should never happen, but check it so that pos[-1] is valid:
+ if (num_positive_leaps == 0) [[unlikely]]
+ return false;
+
+ // Convert utc_time to sys_time:
+ sys_seconds ss(secs - info.elapsed);
+ // See if that sys_time is before (or during) previous leap sec:
+ if (ss < pos[-1])
+ {
+ if ((ss + 1s) >= pos[-1])
+ info.is_leap_second = true;
+ else
+ info.elapsed -= pos[-1].value();
+ }
+ }
+ return true;
+ };
+
+ using _Node = tzdb_list::_Node;
+
+ // If the caller was compiled using an older GCC with an older expiry
+ // time in the header than the `fixed_expiry` defined above, we might
+ // be able to answer the query easily using the static `fixed_leaps`.
+ if (secs <= fixed_expiry)
+ return update_info(_Node::fixed_leaps);
+
+ constexpr auto num_fixed_leaps = std::size(_Node::fixed_leaps);
+
+ auto num_leaps = num_leap_seconds.load(memory_order::relaxed);
+ if (num_leaps == num_fixed_leaps)
+ // A leapseconds file has been read and has no new leap seconds:
+ return update_info(_Node::fixed_leaps);
+ else if (num_leaps != 0)
+ // The tzdb_list has been initialized and contains a tzdb object
+ // with new leap seconds, which we want to use here.
+ // The relaxed load above does not synchronize with anything, so to
+ // ensure that the get_tzdb_list() below will see a tzdb object set
+ // by _S_replace_head, we load num_leap_seconds again with acquire
+ // ordering:
+ (void) num_leap_seconds.load(memory_order::acquire);
+ else
+ {
+ // The tzdb_list has not been initialized yet, so we don't know
+ // the correct number of leap seconds.
+ // We use _S_read_leap_seconds() to read the leapseconds file.
+ // If that tells us there are no new leapseconds, we don't need
+ // to parse all of tzdata.zi and initialize a whole tzdb object.
+ if (_Node::_S_read_leap_seconds().first.size() == num_fixed_leaps)
+ {
+ // There are no new leap seconds. remember that so that the next
+ // call to this function can just use fixed_leaps.
+ num_leap_seconds.compare_exchange_strong(num_leaps,
+ num_fixed_leaps,
+ memory_order::relaxed);
+ return update_info(_Node::fixed_leaps);
+ }
+ // else there are new leap seconds. We init tzdb_list so that the
+ // new leap seconds are persisted in a tzdb object.
+ }
+
+ // Use updated leap_seconds from tzdb.
+ return update_info(get_tzdb_list().begin()->leap_seconds);
+ }
+ }
+
// Return leap_second values, and a bool indicating whether the values are
// current (true), or potentially out of date (false).
pair<vector<leap_second>, bool>
tzdb_list::_Node::_S_read_leap_seconds()
{
- // This list is valid until at least 2026-12-28 00:00:00 UTC.
- constexpr auto expires = sys_days{2026y/12/28};
- vector<leap_second> leaps
- {
- (leap_second) 78796800, // 1 Jul 1972
- (leap_second) 94694400, // 1 Jan 1973
- (leap_second) 126230400, // 1 Jan 1974
- (leap_second) 157766400, // 1 Jan 1975
- (leap_second) 189302400, // 1 Jan 1976
- (leap_second) 220924800, // 1 Jan 1977
- (leap_second) 252460800, // 1 Jan 1978
- (leap_second) 283996800, // 1 Jan 1979
- (leap_second) 315532800, // 1 Jan 1980
- (leap_second) 362793600, // 1 Jul 1981
- (leap_second) 394329600, // 1 Jul 1982
- (leap_second) 425865600, // 1 Jul 1983
- (leap_second) 489024000, // 1 Jul 1985
- (leap_second) 567993600, // 1 Jan 1988
- (leap_second) 631152000, // 1 Jan 1990
- (leap_second) 662688000, // 1 Jan 1991
- (leap_second) 709948800, // 1 Jul 1992
- (leap_second) 741484800, // 1 Jul 1993
- (leap_second) 773020800, // 1 Jul 1994
- (leap_second) 820454400, // 1 Jan 1996
- (leap_second) 867715200, // 1 Jul 1997
- (leap_second) 915148800, // 1 Jan 1999
- (leap_second)1136073600, // 1 Jan 2006
- (leap_second)1230768000, // 1 Jan 2009
- (leap_second)1341100800, // 1 Jul 2012
- (leap_second)1435708800, // 1 Jul 2015
- (leap_second)1483228800, // 1 Jan 2017
- };
+ // Populate the vector with the leap seconds we already know about:
+ vector<leap_second> leaps(fixed_leaps, std::end(fixed_leaps));
-#if 0
- // This optimization isn't valid if the file has additional leap seconds
- // defined since the library was compiled, but the system clock has been
- // set to a time before the hardcoded expiration date.
- if (system_clock::now() < expires)
- return {std::move(leaps), true};
-#endif
+ bool read_leaps_file = false;
#ifndef TZDB_DISABLED
if (ifstream ls{zoneinfo_file(leaps_file)})
{
- auto exp_year = year_month_day(expires).year();
+ constexpr year exp_year
+ = year_month_day(sys_days(duration_cast<days>(fixed_expiry))).year();
+
std::string s, w;
s.reserve(80); // Avoid later reallocations.
while (std::getline(ls, s))
if (!s.starts_with("Leap"))
continue;
+
istringstream li(std::move(s));
li.exceptions(ios::failbit);
li.ignore(4);
leaps.push_back(ls);
}
}
- s = std::move(li).str(); // return storage to s
+ s = std::move(li).str(); // give allocated storage back to s
}
- return {std::move(leaps), true};
+
+ read_leaps_file = true;
}
#endif
- return {std::move(leaps), false};
+
+ return {std::move(leaps), read_leaps_file};
}
#ifndef TZDB_DISABLED
_S_head_owner = std::move(new_head);
#endif
_S_cache_list_head(new_head_ptr);
+
+ // This allows __recent_leap_second_info() to know that it can use
+ // get_tzdb_list()->begin()->leap_seconds to get new leap seconds.
+ // The release op here synchronizes with the acquire op there.
+ num_leap_seconds.store(new_head_ptr->db.leap_seconds.size(),
+ memory_order::release);
+
return new_head_ptr->db;
}
--- /dev/null
+// { dg-do run { target c++20 } }
+// { dg-require-effective-target tzdb }
+// { dg-require-effective-target cxx11_abi }
+// { dg-xfail-run-if "no weak override on AIX" { powerpc-ibm-aix* } }
+
+#include <chrono>
+#include <fstream>
+#include <testsuite_hooks.h>
+
+using namespace std::chrono_literals;
+
+static bool override_used = false;
+
+namespace __gnu_cxx
+{
+ const char* zoneinfo_dir_override() {
+ override_used = true;
+ return "./";
+ }
+}
+
+void
+test_known_leaps()
+{
+ // Test some values within the list of known leap seconds.
+ auto s = std::chrono::utc_seconds(-1s);
+ auto lsi = get_leap_second_info(s);
+ VERIFY( lsi.is_leap_second == false );
+ VERIFY( lsi.elapsed == 0s );
+
+ s = std::chrono::utc_seconds(126230402s); // 1 Jan 1974
+ lsi = get_leap_second_info(s);
+ VERIFY( lsi.is_leap_second == true );
+ VERIFY( lsi.elapsed == 3s );
+
+ s = std::chrono::utc_seconds(1483228826s); // 1 Jan 2017
+ lsi = get_leap_second_info(s);
+ VERIFY( lsi.is_leap_second == true );
+ VERIFY( lsi.elapsed == 27s );
+
+ // We should not have checked the filesystem for the times above.
+ VERIFY( ! override_used );
+}
+
+void
+test_future_leaps()
+{
+ // XXX adjust this if real leap seconds are added to the hardcoded lists:
+ const auto hardcoded_count = 27s;
+
+ // Make sure there's no old file from a previous test run.
+ std::ofstream("leapseconds") << "";
+
+ using std::chrono::years;
+ auto s = std::chrono::utc_seconds(1483228826s + years(100)); // 1 Jan 2117
+ auto lsi = get_leap_second_info(s);
+ VERIFY( override_used ); // If this fails then XFAIL for the target.
+ VERIFY( lsi.is_leap_second == false );
+ VERIFY( lsi.elapsed == hardcoded_count );
+ lsi = get_leap_second_info(s + years(10));
+ VERIFY( lsi.is_leap_second == false );
+ VERIFY( lsi.elapsed == hardcoded_count );
+
+ std::ofstream("leapseconds") << R"(
+# No need to repeat the real leap seconds here, they're hardcoded in the lib.
+# These are fake new leap seconds for testing purposes:
+Leap 2099 Dec 31 23:59:60 + S
+Leap 2120 Jun 30 23:59:59 - S
+Leap 2120 Dec 30 23:59:59 - S
+)";
+
+ override_used = false;
+ std::chrono::reload_tzdb();
+ VERIFY( override_used );
+
+ // Check the same dates again using the custom leapseconds file:
+ lsi = get_leap_second_info(s);
+ VERIFY( lsi.is_leap_second == false );
+ VERIFY( lsi.elapsed == hardcoded_count + 1s ); // One positive leap second.
+ lsi = get_leap_second_info(s + years(10));
+ VERIFY( lsi.is_leap_second == false );
+ VERIFY( lsi.elapsed == hardcoded_count - 1s ); // Two negative leap seconds.
+
+ // Overwrite the custom file again:
+ override_used = false;
+ std::ofstream("leapseconds") << "";
+
+ // This should not re-read the custom file, the head of the tzdb_list
+ // should already have been populated by calling get_leap_second_info(s):
+ auto& tzdb = std::chrono::get_tzdb();
+ // The file was not read again:
+ VERIFY( ! override_used );
+ // The list in the tzdb contains the three fake leap seconds:
+ VERIFY( tzdb.leap_seconds.size() == hardcoded_count.count() + 3 );
+ // And repeating the queries above gives the same results:
+ lsi = get_leap_second_info(s);
+ VERIFY( lsi.is_leap_second == false );
+ VERIFY( lsi.elapsed == hardcoded_count + 1s ); // One positive leap second.
+ lsi = get_leap_second_info(s + years(10));
+ VERIFY( lsi.is_leap_second == false );
+ VERIFY( lsi.elapsed == hardcoded_count - 1s ); // Two negative leap seconds.
+}
+
+int main()
+{
+ test_known_leaps();
+ test_future_leaps();
+}
projects / thirdparty / gcc.git / commitdiff
