When seeding zone information from the application of the rules
prior the transition, we should consider the rule triggering exactly
at boundary, not only prior, i.e. call find_active_rule with info.begin.
Due the rule_start - t < days(1) check (that is not removed yet), such
transitions were effectively ignored.
This addresses the regression introduced by r17-2060-gf7cde200320e08,
where new differences between libstdc++ output and date library where
introduced fro some zones (e.g. Europe/Lisbon in 1976). With this fixup,
the patch is now pure improvement in consistency.
libstdc++-v3/ChangeLog:
* src/c++20/tzdb.cc (time_zone::_M_get_sys_info): Find
rules firing exactly at transition time.
* testsuite/std/time/time_zone/wall_cascade.cc: Add test
for Europe/Lisbon, and corrected test_negative.
---
Using your test program, I compared current trunk state with GCC-16
and found that we have new differences caused by my previous patch.
All of them are now addressed. Note that this would most likely be
fixed in follow-up patches, but I think that r17-2060-gf7cde200320e08,
with this fix may be good candidate for backport, as they should not
impact performance.
Testing on x86_64-linux locally. *time_zone* test passed with all
standard modes. OK for trunk?
libstdc++-v3/src/c++20/tzdb.cc | 2 +-
.../std/time/time_zone/wall_cascade.cc | 52 ++++++++++++++++---
2 files changed, 47 insertions(+), 7 deletions(-)
diff --git a/libstdc++-v3/src/c++20/tzdb.cc b/libstdc++-v3/src/c++20/tzdb.cc
index 998a363151d..4ecce9e214e 100644
--- a/libstdc++-v3/src/c++20/tzdb.cc
+++ b/libstdc++-v3/src/c++20/tzdb.cc
@@ -1027,7 +1027,7 @@ namespace std::chrono
// SAVE and LETTERS values. There may not be a Rule for the period
// before the first DST transition, so find the earliest DST->STD
// transition and use the LETTERS from that.
- if (const Rule* active_rule = find_active_rule(rules, info.begin -
seconds(1), ri.offset()))
+ if (const Rule* active_rule = find_active_rule(rules, info.begin,
ri.offset()))
{
info.offset = ri.offset() + active_rule->save;
info.save = chrono::duration_cast<minutes>(active_rule->save);
diff --git a/libstdc++-v3/testsuite/std/time/time_zone/wall_cascade.cc
b/libstdc++-v3/testsuite/std/time/time_zone/wall_cascade.cc
index 2707e3fcd33..f270a13fcad 100644
--- a/libstdc++-v3/testsuite/std/time/time_zone/wall_cascade.cc
+++ b/libstdc++-v3/testsuite/std/time/time_zone/wall_cascade.cc
@@ -76,11 +76,11 @@ test_negative()
// running save.
//
// Two-line zone whose second line begins at 1945 Sep 16 01:00 UT,
- // at the cascaded firing time (Sep 16 01:00 UT), but after
+ // before the cascaded firing time (Sep 16 02:00 UT), but after
// non-cascaded firing time (Sep 16 00:00 UT) of the September rule.
// The seeding must pick the April rule (save=-2, CEST) at info.begin.
std::ofstream("tzdata.zi") << R"(# version test_negative_cascade
-R Fr 1945 o - Apr 2 2 -2 M
+R Fr 1945 o - Apr 2 2 -3 M
R Fr 1945 o - Sep 16 0 0 -
Z Test/Negative 0 - X 1945 Sep 16 1u
1 Fr CE%sT
@@ -96,15 +96,24 @@ Z Test/Negative 0 - X 1945 Sep 16 1u
// one second after.
auto info = tz->get_info(sys_seconds{
sys_days(1945y/September/16) + 1h + 1s});
- VERIFY( info.offset == -1h );
- VERIFY( info.save == -2h );
+ VERIFY( info.offset == -2h );
+ VERIFY( info.save == -3h );
VERIFY( info.abbrev == "CEMT" );
// The boundary instant.
auto at_boundary
= tz->get_info(sys_seconds{sys_days(1945y/September/16) + 1h});
- VERIFY( at_boundary.offset == -1h );
- VERIFY( at_boundary.save == -2h );
+ VERIFY( at_boundary.offset == -2h );
+ VERIFY( at_boundary.save == -3h );
+
+ // Test the firing of Sep 16 rule
+ auto at_sep_rule = tz->get_info(sys_seconds{
+ sys_days(1945y/September/16) + 2h});
+ // The transition_window < 1d condition triggers, and
+ // transition is ignored.
+ // VERIFY( at_sep_rule.offset == 1h );
+ // VERIFY( at_sep_rule.save == 0h );
+ // VERIFY( at_sep_rule.abbrev == "CET" );
}
void
@@ -222,6 +231,36 @@ Z Test/EarielYear 11:39:4 - LMT 1868 N 2
VERIFY( at_boundary.abbrev == "EYMT" );
}
+void
+test_at_boundary()
+{
+ std::ofstream("tzdata.zi") << R"(# version test_at_boundary
+R p 1947 1966 - Ap Su>=1 2s 1 S
+R p 1947 1965 - O Su>=1 2s 0 -
+R p 1976 o - S lastSu 1 0 -
+R p 1977 o - Mar lastSu 0s 1 S
+R p 1977 o - S lastSu 0s 0 -
+Z Europe/Lisbon -0:36:45 - LMT 1884
+1 - CET 1976 S 26 1
+0 p WE%sT 1986
+ )";
+
+ const auto& db = reload_tzdb();
+ VERIFY( override_used ); // If this fails then XFAIL for the target.
+ VERIFY( db.version == "test_at_boundary" );
+
+ // The change from CET to WE%sT line happens 1976 Sep 26 00:00:00 UT,
+ // should take into considration 1976 lastSu rule that fires at the
+ // same time (running save is 1h from 1966 Ap rule application),
+ // and start in standard time (WET period).
+ auto* utz = locate_zone("Europe/Lisbon");
+ auto at_boundary
+ = utz->get_info(sys_seconds{sys_days(1976y/September/26) + 0h});
+ VERIFY( at_boundary.offset == 0h );
+ VERIFY( at_boundary.save == 0min );
+ VERIFY( at_boundary.abbrev == "WET" );
+}
+
int
main()
{
@@ -230,4 +269,5 @@ main()
test_next_year();
test_prev_year();
test_earlier_year();
+ test_at_boundary();
}
--
2.55.0
