gcc: add a backport patch to fix an issue with tzdata 2024b

There is an issue in the std::chrono::tzdb parser that causes problems
since the tzdata-2024b release started using %z in the main format.

As a real world problem I encounter an issue with the waybar clock module,
which ignores the timezone setting and only shows system time.

Signed-off-by: Markus Volk <f_l_k@t-online.de>
---
 meta/recipes-devtools/gcc/gcc-14.2.inc        |   1 +
 ...4fffe3fc82a710bea66ad651720d71c938b8.patch | 567 ++++++++++++++++++
 2 files changed, 568 insertions(+)
 create mode 100644 meta/recipes-devtools/gcc/gcc/gcc.git-ab884fffe3fc82a710bea66ad651720d71c938b8.patch

Should the backport of tzdata update like
https://lists.openembedded.org/g/openembedded-core/message/207561
for scarthgap and
https://lists.openembedded.org/g/openembedded-core/message/207428
for styhead be delayed a bit so that this gcc change can go at the same time?

I don't know how widespread this is (or what is waybar clock module),
but the .patch says:

+Since making this change on trunk, the tzdata-2024b release started
+using %z in the main format, not just vanguard. This makes a backport to
+release branches necessary (see PR 116657).

+Steve Sakoman

On Fri, Nov 22, 2024 at 2:30 AM Markus Volk via lists.openembedded.org
<f_l_k=t-online.de@lists.openembedded.org> wrote:
>
> There is an issue in the std::chrono::tzdb parser that causes problems
> since the tzdata-2024b release started using %z in the main format.
>
> As a real world problem I encounter an issue with the waybar clock module,
> which ignores the timezone setting and only shows system time.
>
> Signed-off-by: Markus Volk <f_l_k@t-online.de>
> ---
>  meta/recipes-devtools/gcc/gcc-14.2.inc        |   1 +
>  ...4fffe3fc82a710bea66ad651720d71c938b8.patch | 567 ++++++++++++++++++
>  2 files changed, 568 insertions(+)
>  create mode 100644 meta/recipes-devtools/gcc/gcc/gcc.git-ab884fffe3fc82a710bea66ad651720d71c938b8.patch
>
> diff --git a/meta/recipes-devtools/gcc/gcc-14.2.inc b/meta/recipes-devtools/gcc/gcc-14.2.inc
> index f05484cfc0..9cfb246294 100644
> --- a/meta/recipes-devtools/gcc/gcc-14.2.inc
> +++ b/meta/recipes-devtools/gcc/gcc-14.2.inc
> @@ -68,6 +68,7 @@ SRC_URI = "${BASEURI} \
>             file://0023-Fix-install-path-of-linux64.h.patch \
>             file://0024-Avoid-hardcoded-build-paths-into-ppc-libgcc.patch \
>             file://0025-gcc-testsuite-tweaks-for-mips-OE.patch \
> +           file://gcc.git-ab884fffe3fc82a710bea66ad651720d71c938b8.patch \
>  "
>
>  S = "${TMPDIR}/work-shared/gcc-${PV}-${PR}/${SOURCEDIR}"
> diff --git a/meta/recipes-devtools/gcc/gcc/gcc.git-ab884fffe3fc82a710bea66ad651720d71c938b8.patch b/meta/recipes-devtools/gcc/gcc/gcc.git-ab884fffe3fc82a710bea66ad651720d71c938b8.patch
> new file mode 100644
> index 0000000000..ca6fc92e07
> --- /dev/null
> +++ b/meta/recipes-devtools/gcc/gcc/gcc.git-ab884fffe3fc82a710bea66ad651720d71c938b8.patch
> @@ -0,0 +1,567 @@
> +From ab884fffe3fc82a710bea66ad651720d71c938b8 Mon Sep 17 00:00:00 2001
> +From: Jonathan Wakely <jwakely@redhat.com>
> +Date: Tue, 30 Apr 2024 09:52:13 +0100
> +Subject: [PATCH] libstdc++: Fix std::chrono::tzdb to work with vanguard format
> +
> +I found some issues in the std::chrono::tzdb parser by testing the
> +tzdata "vanguard" format, which uses new features that aren't enabled in
> +the "main" and "rearguard" data formats.
> +
> +Since 2024a the keyword "minimum" is no longer valid for the FROM and TO
> +fields in a Rule line, which means that "m" is now a valid abbreviation
> +for "maximum". Previously we expected either "mi" or "ma". For backwards
> +compatibility, a FROM field beginning with "mi" is still supported and
> +is treated as 1900. The "maximum" keyword is only allowed in TO now,
> +because it makes no sense in FROM. To support these changes the
> +minmax_year and minmax_year2 classes for parsing FROM and TO are
> +replaced with a single years_from_to class that reads both fields.
> +
> +The vanguard format makes use of %z in Zone FORMAT fields, which caused
> +an exception to be thrown from ZoneInfo::set_abbrev because no % or /
> +characters were expected when a Zone doesn't use a named Rule. The
> +ZoneInfo::to(sys_info&) function now uses format_abbrev_str to replace
> +any %z with the current offset. Although format_abbrev_str also checks
> +for %s and STD/DST formats, those only make sense when a named Rule is
> +in effect, so won't occur when ZoneInfo::to(sys_info&) is used.
> +
> +Since making this change on trunk, the tzdata-2024b release started
> +using %z in the main format, not just vanguard. This makes a backport to
> +release branches necessary (see PR 116657).
> +
> +This change also implements a feature that has always been missing from
> +time_zone::_M_get_sys_info: finding the Rule that is active before the
> +specified time point, so that we can correctly handle %s in the FORMAT
> +for the first new sys_info that gets created. This requires implementing
> +a poorly documented feature of zic, to get the LETTERS field from a
> +later transition, as described at
> +https://mm.icann.org/pipermail/tz/2024-April/058891.html
> +In order for this to work we need to be able to distinguish an empty
> +letters field (as used by CE%sT where the variable part is either empty
> +or "S") from "the letters field is not known for this transition". The
> +tzdata file uses "-" for an empty letters field, which libstdc++ was
> +previously replacing with "" when the Rule was parsed. Instead, we now
> +preserve the "-" in the Rule object, so that "" can be used for the case
> +where we don't know the letters (and so need to decide it).
> +
> +libstdc++-v3/ChangeLog:
> +
> +       * src/c++20/tzdb.cc (minmax_year, minmax_year2): Remove.
> +       (years_from_to): New class replacing minmax_year and
> +       minmax_year2.
> +       (format_abbrev_str, select_std_or_dst_abbrev): Move earlier in
> +       the file. Handle "-" for letters.
> +       (ZoneInfo::to): Use format_abbrev_str to expand %z.
> +       (ZoneInfo::set_abbrev): Remove exception. Change parameter from
> +       reference to value.
> +       (operator>>(istream&, Rule&)): Do not clear letters when it
> +       contains "-".
> +       (time_zone::_M_get_sys_info): Add missing logic to find the Rule
> +       in effect before the time point.
> +       * testsuite/std/time/tzdb/1.cc: Adjust for vanguard format using
> +       "GMT" as the Zone name, not as a Link to "Etc/GMT".
> +       * testsuite/std/time/time_zone/sys_info_abbrev.cc: New test.
> +
> +(cherry picked from commit 0ca8d56f2085715f27ee536c6c344bc47af49cdd)
> +
> +Upstream-Status: Backport [https://gcc.gnu.org/git/gitweb.cgi?p=gcc.git;h=5ceea2ac106d6dd1aa8175670b15a801316cf1c9]
> +
> +Signed-off-by: Markus Volk <f_l_k@t-online.de>
> +---
> + libstdc++-v3/src/c++20/tzdb.cc                | 265 +++++++++++-------
> + .../std/time/time_zone/sys_info_abbrev.cc     | 106 +++++++
> + libstdc++-v3/testsuite/std/time/tzdb/1.cc     |   6 +-
> + 3 files changed, 274 insertions(+), 103 deletions(-)
> + create mode 100644 libstdc++-v3/testsuite/std/time/time_zone/sys_info_abbrev.cc
> +
> +diff --git a/libstdc++-v3/src/c++20/tzdb.cc b/libstdc++-v3/src/c++20/tzdb.cc
> +index c7c7cc9deee6..7e8cce7ce8cf 100644
> +--- a/libstdc++-v3/src/c++20/tzdb.cc
> ++++ b/libstdc++-v3/src/c++20/tzdb.cc
> +@@ -342,51 +342,103 @@ namespace std::chrono
> +       friend istream& operator>>(istream&, on_day&);
> +     };
> +
> +-    // Wrapper for chrono::year that reads a year, or one of the keywords
> +-    // "minimum" or "maximum", or an unambiguous prefix of a keyword.
> +-    struct minmax_year
> ++    // Wrapper for two chrono::year values, which reads the FROM and TO
> ++    // fields of a Rule line. The FROM field is a year and TO is a year or
> ++    // one of the keywords "maximum" or "only" (or an abbreviation of those).
> ++    // For backwards compatibility, the keyword "minimum" is recognized
> ++    // for FROM and interpreted as 1900.
> ++    struct years_from_to
> +     {
> +-      year& y;
> ++      year& from;
> ++      year& to;
> +
> +-      friend istream& operator>>(istream& in, minmax_year&& y)
> ++      friend istream& operator>>(istream& in, years_from_to&& yy)
> +       {
> +-      if (ws(in).peek() == 'm') // keywords "minimum" or "maximum"
> ++      string s;
> ++      auto c = ws(in).peek();
> ++      if (c == 'm') [[unlikely]] // keyword "minimum"
> +         {
> +-          string s;
> +-          in >> s; // extract the rest of the word, but only look at s[1]
> +-          if (s[1] == 'a')
> +-            y.y = year::max();
> +-          else if (s[1] == 'i')
> +-            y.y = year::min();
> +-          else
> +-            in.setstate(ios::failbit);
> ++          in >> s; // extract the rest of the word
> ++          yy.from = year(1900);
> ++        }
> ++      else if (int num = 0; in >> num) [[likely]]
> ++        yy.from = year{num};
> ++
> ++      c = ws(in).peek();
> ++      if (c == 'm') // keyword "maximum"
> ++        {
> ++          in >> s; // extract the rest of the word
> ++          yy.to = year::max();
> ++        }
> ++      else if (c == 'o') // keyword "only"
> ++        {
> ++          in >> s; // extract the rest of the word
> ++          yy.to = yy.from;
> +         }
> +       else if (int num = 0; in >> num)
> +-        y.y = year{num};
> ++        yy.to = year{num};
> ++
> +       return in;
> +       }
> +     };
> +
> +-    // As above for minmax_year, but also supports the keyword "only",
> +-    // meaning that the TO year is the same as the FROM year.
> +-    struct minmax_year2
> ++    bool
> ++    select_std_or_dst_abbrev(string& abbrev, minutes save)
> +     {
> +-      minmax_year to;
> +-      year from;
> ++      if (size_t pos = abbrev.find('/'); pos != string::npos)
> ++      {
> ++        // Select one of "STD/DST" for standard or daylight.
> ++        if (save == 0min)
> ++          abbrev.erase(pos);
> ++        else
> ++          abbrev.erase(0, pos + 1);
> ++        return true;
> ++      }
> ++      return false;
> ++    }
> +
> +-      friend istream& operator>>(istream& in, minmax_year2&& y)
> +-      {
> +-      if (ws(in).peek() == 'o') // keyword "only"
> +-        {
> +-          string s;
> +-          in >> s; // extract the whole keyword
> +-          y.to.y = y.from;
> +-        }
> +-      else
> +-        in >> std::move(y.to);
> +-      return in;
> +-      }
> +-    };
> ++    // Set the sys_info::abbrev string by expanding any placeholders.
> ++    void
> ++    format_abbrev_str(sys_info& info, string_view letters = {})
> ++    {
> ++      if (size_t pos = info.abbrev.find('%'); pos != string::npos)
> ++      {
> ++        if (info.abbrev[pos + 1] == 's')
> ++          {
> ++            // Expand "%s" to the variable part, given by Rule::letters.
> ++            if (letters == "-")
> ++              info.abbrev.erase(pos, 2);
> ++            else
> ++              info.abbrev.replace(pos, 2, letters);
> ++          }
> ++        else if (info.abbrev[pos + 1] == 'z')
> ++          {
> ++            // Expand "%z" to the UT offset as +/-hh, +/-hhmm, or +/-hhmmss.
> ++            hh_mm_ss<seconds> t(info.offset);
> ++            string z(1, "+-"[t.is_negative()]);
> ++            long val = t.hours().count();
> ++            int digits = 2;
> ++            if (int m = t.minutes().count())
> ++              {
> ++                digits = 4;
> ++                val *= 100;
> ++                val += m;
> ++                if (int s = t.seconds().count())
> ++                  {
> ++                    digits = 6;
> ++                    val *= 100;
> ++                    val += s;
> ++                  }
> ++              }
> ++            auto sval = std::to_string(val);
> ++            z += string(digits - sval.size(), '0');
> ++            z += sval;
> ++            info.abbrev.replace(pos, 2, z);
> ++          }
> ++      }
> ++      else
> ++      select_std_or_dst_abbrev(info.abbrev, info.save);
> ++    }
> +
> +     // A time zone information record.
> +     // Zone  NAME        STDOFF  RULES   FORMAT  [UNTIL]
> +@@ -462,6 +514,7 @@ namespace std::chrono
> +       info.offset = offset();
> +       info.save = minutes(m_save);
> +       info.abbrev = format();
> ++      format_abbrev_str(info); // expand %z
> +       return true;
> +       }
> +
> +@@ -469,12 +522,9 @@ namespace std::chrono
> +       friend class time_zone;
> +
> +       void
> +-      set_abbrev(const string& abbrev)
> ++      set_abbrev(string abbrev)
> +       {
> +-      // In practice, the FORMAT field never needs expanding here.
> +-      if (abbrev.find_first_of("/%") != abbrev.npos)
> +-        __throw_runtime_error("std::chrono::time_zone: invalid data");
> +-      m_buf = abbrev;
> ++      m_buf = std::move(abbrev);
> +       m_pos = 0;
> +       m_expanded = true;
> +       }
> +@@ -544,9 +594,7 @@ namespace std::chrono
> +
> +       // Rule  NAME  FROM  TO  TYPE  IN  ON  AT  SAVE  LETTER/S
> +
> +-      in >> quoted(rule.name)
> +-         >> minmax_year{rule.from}
> +-         >> minmax_year2{rule.to, rule.from};
> ++      in >> quoted(rule.name) >> years_from_to{rule.from, rule.to};
> +
> +       if (char type; in >> type && type != '-')
> +         in.setstate(ios::failbit);
> +@@ -557,7 +605,7 @@ namespace std::chrono
> +       if (save_time.indicator != at_time::Wall)
> +         {
> +           // We don't actually store the save_time.indicator, because we
> +-          // assume that it's always deducable from the actual offset value.
> ++          // assume that it's always deducible from the offset value.
> +           auto expected = save_time.time == 0s
> +                             ? at_time::Standard
> +                             : at_time::Daylight;
> +@@ -567,8 +615,6 @@ namespace std::chrono
> +       rule.save = save_time.time;
> +
> +       in >> rule.letters;
> +-      if (rule.letters == "-")
> +-        rule.letters.clear();
> +       return in;
> +       }
> +
> +@@ -719,58 +765,6 @@ namespace std::chrono
> + #endif // TZDB_DISABLED
> +   };
> +
> +-#ifndef TZDB_DISABLED
> +-  namespace
> +-  {
> +-    bool
> +-    select_std_or_dst_abbrev(string& abbrev, minutes save)
> +-    {
> +-      if (size_t pos = abbrev.find('/'); pos != string::npos)
> +-      {
> +-        // Select one of "STD/DST" for standard or daylight.
> +-        if (save == 0min)
> +-          abbrev.erase(pos);
> +-        else
> +-          abbrev.erase(0, pos + 1);
> +-        return true;
> +-      }
> +-      return false;
> +-    }
> +-
> +-    // Set the sys_info::abbrev string by expanding any placeholders.
> +-    void
> +-    format_abbrev_str(sys_info& info, string_view letters = {})
> +-    {
> +-      if (size_t pos = info.abbrev.find("%s"); pos != string::npos)
> +-      {
> +-        // Expand "%s" to the variable part, given by Rule::letters.
> +-        info.abbrev.replace(pos, 2, letters);
> +-      }
> +-      else if (size_t pos = info.abbrev.find("%z"); pos != string::npos)
> +-      {
> +-        // Expand "%z" to the UT offset as +/-hh, +/-hhmm, or +/-hhmmss.
> +-        hh_mm_ss<seconds> t(info.offset);
> +-        string z(1, "+-"[t.is_negative()]);
> +-        long val = t.hours().count();
> +-        if (minutes m = t.minutes(); m != m.zero())
> +-          {
> +-            val *= 100;
> +-            val += m.count();
> +-            if (seconds s = t.seconds(); s != s.zero())
> +-              {
> +-                val *= 100;
> +-                val += s.count();
> +-              }
> +-          }
> +-        z += std::to_string(val);
> +-        info.abbrev.replace(pos, 2, z);
> +-      }
> +-      else
> +-      select_std_or_dst_abbrev(info.abbrev, info.save);
> +-    }
> +-  }
> +-#endif // TZDB_DISABLED
> +-
> +   // Implementation of std::chrono::time_zone::get_info(const sys_time<D>&)
> +   sys_info
> +   time_zone::_M_get_sys_info(sys_seconds tp) const
> +@@ -839,12 +833,72 @@ namespace std::chrono
> +     info.abbrev = ri.format();
> +
> +     string_view letters;
> +-    if (i != infos.begin())
> ++    if (i != infos.begin() && i[-1].expanded())
> ++      letters = i[-1].next_letters();
> ++
> ++    if (letters.empty())
> +       {
> +-      if (i[-1].expanded())
> +-        letters = i[-1].next_letters();
> +-      // XXX else need to find Rule active before this time and use it
> +-      // to know the initial offset, save, and letters.
> ++      sys_seconds t = info.begin - seconds(1);
> ++      const year_month_day date(chrono::floor<days>(t));
> ++
> ++      // Try to find a Rule active before this time, to get initial
> ++      // 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.
> ++      const Rule* active_rule = nullptr;
> ++      sys_seconds active_rule_start = sys_seconds::min();
> ++      const Rule* first_std = nullptr;
> ++      for (const auto& rule : rules)
> ++        {
> ++          if (rule.save == minutes(0))
> ++            {
> ++              if (!first_std)
> ++                first_std = &rule;
> ++              else if (rule.from < first_std->from)
> ++                first_std = &rule;
> ++              else if (rule.from == first_std->from)
> ++                {
> ++                  if (rule.start_time(rule.from, {})
> ++                        < first_std->start_time(first_std->from, {}))
> ++                    first_std = &rule;
> ++                }
> ++            }
> ++
> ++          year y = date.year();
> ++
> ++          if (y > rule.to) // rule no longer applies at time t
> ++            continue;
> ++          if (y < rule.from) // rule doesn't apply yet at time t
> ++            continue;
> ++
> ++          sys_seconds rule_start;
> ++
> ++          seconds offset{}; // appropriate for at_time::Universal
> ++          if (rule.when.indicator == at_time::Wall)
> ++            offset = info.offset;
> ++          else if (rule.when.indicator == at_time::Standard)
> ++            offset = ri.offset();
> ++
> ++          // Time the rule takes effect this year:
> ++          rule_start = rule.start_time(y, offset);
> ++
> ++          if (rule_start >= t && rule.from < y)
> ++            {
> ++              // Try this rule in the previous year.
> ++              rule_start = rule.start_time(--y, offset);
> ++            }
> ++
> ++          if (active_rule_start < rule_start && rule_start < t)
> ++            {
> ++              active_rule_start = rule_start;
> ++              active_rule = &rule;
> ++            }
> ++        }
> ++
> ++      if (active_rule)
> ++        letters = active_rule->letters;
> ++      else if (first_std)
> ++        letters = first_std->letters;
> +       }
> +
> +     const Rule* curr_rule = nullptr;
> +@@ -2069,9 +2123,11 @@ namespace std::chrono
> +             istringstream in2(std::move(rules));
> +             in2 >> rules_time;
> +             inf.m_save = duration_cast<minutes>(rules_time.time);
> ++            // If the FORMAT is "STD/DST" then we can choose the right one
> ++            // now, so that we store a shorter string.
> +             select_std_or_dst_abbrev(fmt, inf.m_save);
> +           }
> +-        inf.set_abbrev(fmt);
> ++        inf.set_abbrev(std::move(fmt));
> +       }
> +
> +       // YEAR [MONTH [DAY [TIME]]]
> +@@ -2082,7 +2138,12 @@ namespace std::chrono
> +         abbrev_month m{January};
> +         int d = 1;
> +         at_time t{};
> ++        // XXX DAY should support ON format, e.g. lastSun or Sun>=8
> +         in >> m >> d >> t;
> ++        // XXX UNTIL field should be interpreted
> ++        // "using the rules in effect just before the transition"
> ++        // so might need to store as year_month_day and hh_mm_ss and only
> ++        // convert to a sys_time once we know the offset in effect.
> +         inf.m_until = sys_days(year(y)/m.m/day(d)) + seconds(t.time);
> +       }
> +       else
> +diff --git a/libstdc++-v3/testsuite/std/time/time_zone/sys_info_abbrev.cc b/libstdc++-v3/testsuite/std/time/time_zone/sys_info_abbrev.cc
> +new file mode 100644
> +index 000000000000..f1a8fff02f58
> +--- /dev/null
> ++++ b/libstdc++-v3/testsuite/std/time/time_zone/sys_info_abbrev.cc
> +@@ -0,0 +1,106 @@
> ++// { 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>
> ++
> ++static bool override_used = false;
> ++
> ++namespace __gnu_cxx
> ++{
> ++  const char* zoneinfo_dir_override() {
> ++    override_used = true;
> ++    return "./";
> ++  }
> ++}
> ++
> ++using namespace std::chrono;
> ++
> ++void
> ++test_format()
> ++{
> ++  std::ofstream("tzdata.zi") << R"(# version test_1
> ++Zone Africa/Bissau -1:2:20 - LMT 1912 Ja 1 1u
> ++                   -1      - %z  1975
> ++                   0       - GMT
> ++Zon Some/Zone 1:2:3   - %z 1900
> ++              1:23:45 - %z 1950
> ++Zo Another/Zone 1:2:3 -     AZ0     1901
> ++                1     Roolz A%sZ    2000
> ++                1     Roolz SAZ/DAZ 2005
> ++                1     Roolz %z
> ++Rule Roolz 1950 max - April 1 2 1 D
> ++Rul  Roolz 1950 max - Oct   1 1 0 S
> ++Z Strange/Zone 1       - X%sX    1980
> ++               1       - FOO/BAR 1990
> ++               2:00    - %zzz    1995
> ++               0:9     - %zzz    1996
> ++               0:8:7   - %zzz    1997
> ++               0:6:5.5 - %zzz    1998
> ++)";
> ++
> ++  const auto& db = reload_tzdb();
> ++  VERIFY( override_used ); // If this fails then XFAIL for the target.
> ++  VERIFY( db.version == "test_1" );
> ++
> ++  // Test formatting %z as
> ++  auto tz = locate_zone("Africa/Bissau");
> ++  auto inf = tz->get_info(sys_days(1974y/1/1));
> ++  VERIFY( inf.abbrev == "-01" );
> ++
> ++  tz = locate_zone("Some/Zone");
> ++  inf = tz->get_info(sys_days(1899y/1/1));
> ++  VERIFY( inf.abbrev == "+010203" );
> ++  inf = tz->get_info(sys_days(1955y/1/1));
> ++  VERIFY( inf.abbrev == "+012345" );
> ++
> ++  tz = locate_zone("Another/Zone");
> ++  // Test formatting %s as the LETTER/S field from the active Rule.
> ++  inf = tz->get_info(sys_days(1910y/January/1));
> ++  VERIFY( inf.abbrev == "ASZ" );
> ++  inf = tz->get_info(sys_days(1950y/January/1));
> ++  VERIFY( inf.abbrev == "ASZ" );
> ++  inf = tz->get_info(sys_days(1950y/June/1));
> ++  VERIFY( inf.abbrev == "ADZ" );
> ++  inf = tz->get_info(sys_days(1999y/January/1));
> ++  VERIFY( inf.abbrev == "ASZ" );
> ++  inf = tz->get_info(sys_days(1999y/July/1));
> ++  VERIFY( inf.abbrev == "ADZ" );
> ++  // Test formatting STD/DST according to the active Rule.
> ++  inf = tz->get_info(sys_days(2000y/January/2));
> ++  VERIFY( inf.abbrev == "SAZ" );
> ++  inf = tz->get_info(sys_days(2001y/January/1));
> ++  VERIFY( inf.abbrev == "SAZ" );
> ++  inf = tz->get_info(sys_days(2001y/July/1));
> ++  VERIFY( inf.abbrev == "DAZ" );
> ++  // Test formatting %z as the offset determined by the active Rule.
> ++  inf = tz->get_info(sys_days(2005y/January/2));
> ++  VERIFY( inf.abbrev == "+01" );
> ++  inf = tz->get_info(sys_days(2006y/January/1));
> ++  VERIFY( inf.abbrev == "+01" );
> ++  inf = tz->get_info(sys_days(2006y/July/1));
> ++  VERIFY( inf.abbrev == "+02" );
> ++
> ++  // Test formatting %z, %s and S/D for a Zone with no associated Rules.
> ++  tz = locate_zone("Strange/Zone");
> ++  inf = tz->get_info(sys_days(1979y/January/1));
> ++  VERIFY( inf.abbrev == "XX" ); // No Rule means nothing to use for %s.
> ++  inf = tz->get_info(sys_days(1981y/July/1));
> ++  VERIFY( inf.abbrev == "FOO" ); // Always standard time means first string.
> ++  inf = tz->get_info(sys_days(1994y/July/1));
> ++  VERIFY( inf.abbrev == "+02zz" );
> ++  inf = tz->get_info(sys_days(1995y/July/1));
> ++  VERIFY( inf.abbrev == "+0009zz" );
> ++  inf = tz->get_info(sys_days(1996y/July/1));
> ++  VERIFY( inf.abbrev == "+000807zz" );
> ++  inf = tz->get_info(sys_days(1997y/July/1));
> ++  VERIFY( inf.abbrev == "+000606zz" );
> ++}
> ++
> ++int main()
> ++{
> ++  test_format();
> ++}
> +diff --git a/libstdc++-v3/testsuite/std/time/tzdb/1.cc b/libstdc++-v3/testsuite/std/time/tzdb/1.cc
> +index 796f3a8b4256..7a31c1c20ba7 100644
> +--- a/libstdc++-v3/testsuite/std/time/tzdb/1.cc
> ++++ b/libstdc++-v3/testsuite/std/time/tzdb/1.cc
> +@@ -39,11 +39,15 @@ test_locate()
> +   const tzdb& db = get_tzdb();
> +   const time_zone* tz = db.locate_zone("GMT");
> +   VERIFY( tz != nullptr );
> +-  VERIFY( tz->name() == "Etc/GMT" );
> +   VERIFY( tz == std::chrono::locate_zone("GMT") );
> +   VERIFY( tz == db.locate_zone("Etc/GMT") );
> +   VERIFY( tz == db.locate_zone("Etc/GMT+0") );
> +
> ++  // Since 2022f GMT is now a Zone and Etc/GMT a link instead of vice versa,
> ++  // but only when using the vanguard format. As of 2024a, the main and
> ++  // rearguard formats still have Etc/GMT as a Zone and GMT as a link.
> ++  VERIFY( tz->name() == "GMT" || tz->name() == "Etc/GMT" );
> ++
> +   VERIFY( db.locate_zone(db.current_zone()->name()) == db.current_zone() );
> + }
> +
> +--
> +2.43.5
> +
> --
> 2.47.0
>
>
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>

On Fri, Nov 22 2024 at 02:35:37 AM +01:00:00, Martin Jansa 
<martin.jansa@gmail.com> wrote:
> I don't know how widespread this is (or what is waybar clock module)


The issue was discussed here

<https://github.com/Alexays/Waybar/issues/3024>

Patch is fine however I would suggest to remove the hunk changing
changellog files it will make it easy to backport

On Thu, Nov 21, 2024 at 5:30 PM Markus Volk via lists.openembedded.org
<f_l_k=t-online.de@lists.openembedded.org> wrote:

> There is an issue in the std::chrono::tzdb parser that causes problems
> since the tzdata-2024b release started using %z in the main format.
>
> As a real world problem I encounter an issue with the waybar clock module,
> which ignores the timezone setting and only shows system time.
>
> Signed-off-by: Markus Volk <f_l_k@t-online.de>
> ---
>  meta/recipes-devtools/gcc/gcc-14.2.inc        |   1 +
>  ...4fffe3fc82a710bea66ad651720d71c938b8.patch | 567 ++++++++++++++++++
>  2 files changed, 568 insertions(+)
>  create mode 100644
> meta/recipes-devtools/gcc/gcc/gcc.git-ab884fffe3fc82a710bea66ad651720d71c938b8.patch
>
> diff --git a/meta/recipes-devtools/gcc/gcc-14.2.inc
> b/meta/recipes-devtools/gcc/gcc-14.2.inc
> index f05484cfc0..9cfb246294 100644
> --- a/meta/recipes-devtools/gcc/gcc-14.2.inc
> +++ b/meta/recipes-devtools/gcc/gcc-14.2.inc
> @@ -68,6 +68,7 @@ SRC_URI = "${BASEURI} \
>             file://0023-Fix-install-path-of-linux64.h.patch \
>             file://0024-Avoid-hardcoded-build-paths-into-ppc-libgcc.patch \
>             file://0025-gcc-testsuite-tweaks-for-mips-OE.patch \
> +           file://gcc.git-ab884fffe3fc82a710bea66ad651720d71c938b8.patch \
>  "
>
>  S = "${TMPDIR}/work-shared/gcc-${PV}-${PR}/${SOURCEDIR}"
> diff --git
> a/meta/recipes-devtools/gcc/gcc/gcc.git-ab884fffe3fc82a710bea66ad651720d71c938b8.patch
> b/meta/recipes-devtools/gcc/gcc/gcc.git-ab884fffe3fc82a710bea66ad651720d71c938b8.patch
> new file mode 100644
> index 0000000000..ca6fc92e07
> --- /dev/null
> +++
> b/meta/recipes-devtools/gcc/gcc/gcc.git-ab884fffe3fc82a710bea66ad651720d71c938b8.patch
> @@ -0,0 +1,567 @@
> +From ab884fffe3fc82a710bea66ad651720d71c938b8 Mon Sep 17 00:00:00 2001
> +From: Jonathan Wakely <jwakely@redhat.com>
> +Date: Tue, 30 Apr 2024 09:52:13 +0100
> +Subject: [PATCH] libstdc++: Fix std::chrono::tzdb to work with vanguard
> format
> +
> +I found some issues in the std::chrono::tzdb parser by testing the
> +tzdata "vanguard" format, which uses new features that aren't enabled in
> +the "main" and "rearguard" data formats.
> +
> +Since 2024a the keyword "minimum" is no longer valid for the FROM and TO
> +fields in a Rule line, which means that "m" is now a valid abbreviation
> +for "maximum". Previously we expected either "mi" or "ma". For backwards
> +compatibility, a FROM field beginning with "mi" is still supported and
> +is treated as 1900. The "maximum" keyword is only allowed in TO now,
> +because it makes no sense in FROM. To support these changes the
> +minmax_year and minmax_year2 classes for parsing FROM and TO are
> +replaced with a single years_from_to class that reads both fields.
> +
> +The vanguard format makes use of %z in Zone FORMAT fields, which caused
> +an exception to be thrown from ZoneInfo::set_abbrev because no % or /
> +characters were expected when a Zone doesn't use a named Rule. The
> +ZoneInfo::to(sys_info&) function now uses format_abbrev_str to replace
> +any %z with the current offset. Although format_abbrev_str also checks
> +for %s and STD/DST formats, those only make sense when a named Rule is
> +in effect, so won't occur when ZoneInfo::to(sys_info&) is used.
> +
> +Since making this change on trunk, the tzdata-2024b release started
> +using %z in the main format, not just vanguard. This makes a backport to
> +release branches necessary (see PR 116657).
> +
> +This change also implements a feature that has always been missing from
> +time_zone::_M_get_sys_info: finding the Rule that is active before the
> +specified time point, so that we can correctly handle %s in the FORMAT
> +for the first new sys_info that gets created. This requires implementing
> +a poorly documented feature of zic, to get the LETTERS field from a
> +later transition, as described at
> +https://mm.icann.org/pipermail/tz/2024-April/058891.html
> +In order for this to work we need to be able to distinguish an empty
> +letters field (as used by CE%sT where the variable part is either empty
> +or "S") from "the letters field is not known for this transition". The
> +tzdata file uses "-" for an empty letters field, which libstdc++ was
> +previously replacing with "" when the Rule was parsed. Instead, we now
> +preserve the "-" in the Rule object, so that "" can be used for the case
> +where we don't know the letters (and so need to decide it).
> +
> +libstdc++-v3/ChangeLog:
> +
> +       * src/c++20/tzdb.cc (minmax_year, minmax_year2): Remove.
> +       (years_from_to): New class replacing minmax_year and
> +       minmax_year2.
> +       (format_abbrev_str, select_std_or_dst_abbrev): Move earlier in
> +       the file. Handle "-" for letters.
> +       (ZoneInfo::to): Use format_abbrev_str to expand %z.
> +       (ZoneInfo::set_abbrev): Remove exception. Change parameter from
> +       reference to value.
> +       (operator>>(istream&, Rule&)): Do not clear letters when it
> +       contains "-".
> +       (time_zone::_M_get_sys_info): Add missing logic to find the Rule
> +       in effect before the time point.
> +       * testsuite/std/time/tzdb/1.cc: Adjust for vanguard format using
> +       "GMT" as the Zone name, not as a Link to "Etc/GMT".
> +       * testsuite/std/time/time_zone/sys_info_abbrev.cc: New test.
> +
> +(cherry picked from commit 0ca8d56f2085715f27ee536c6c344bc47af49cdd)
> +
> +Upstream-Status: Backport [
> https://gcc.gnu.org/git/gitweb.cgi?p=gcc.git;h=5ceea2ac106d6dd1aa8175670b15a801316cf1c9
> ]
> +
> +Signed-off-by: Markus Volk <f_l_k@t-online.de>
> +---
> + libstdc++-v3/src/c++20/tzdb.cc                | 265 +++++++++++-------
> + .../std/time/time_zone/sys_info_abbrev.cc     | 106 +++++++
> + libstdc++-v3/testsuite/std/time/tzdb/1.cc     |   6 +-
> + 3 files changed, 274 insertions(+), 103 deletions(-)
> + create mode 100644
> libstdc++-v3/testsuite/std/time/time_zone/sys_info_abbrev.cc
> +
> +diff --git a/libstdc++-v3/src/c++20/tzdb.cc
> b/libstdc++-v3/src/c++20/tzdb.cc
> +index c7c7cc9deee6..7e8cce7ce8cf 100644
> +--- a/libstdc++-v3/src/c++20/tzdb.cc
> ++++ b/libstdc++-v3/src/c++20/tzdb.cc
> +@@ -342,51 +342,103 @@ namespace std::chrono
> +       friend istream& operator>>(istream&, on_day&);
> +     };
> +
> +-    // Wrapper for chrono::year that reads a year, or one of the keywords
> +-    // "minimum" or "maximum", or an unambiguous prefix of a keyword.
> +-    struct minmax_year
> ++    // Wrapper for two chrono::year values, which reads the FROM and TO
> ++    // fields of a Rule line. The FROM field is a year and TO is a year
> or
> ++    // one of the keywords "maximum" or "only" (or an abbreviation of
> those).
> ++    // For backwards compatibility, the keyword "minimum" is recognized
> ++    // for FROM and interpreted as 1900.
> ++    struct years_from_to
> +     {
> +-      year& y;
> ++      year& from;
> ++      year& to;
> +
> +-      friend istream& operator>>(istream& in, minmax_year&& y)
> ++      friend istream& operator>>(istream& in, years_from_to&& yy)
> +       {
> +-      if (ws(in).peek() == 'm') // keywords "minimum" or "maximum"
> ++      string s;
> ++      auto c = ws(in).peek();
> ++      if (c == 'm') [[unlikely]] // keyword "minimum"
> +         {
> +-          string s;
> +-          in >> s; // extract the rest of the word, but only look at s[1]
> +-          if (s[1] == 'a')
> +-            y.y = year::max();
> +-          else if (s[1] == 'i')
> +-            y.y = year::min();
> +-          else
> +-            in.setstate(ios::failbit);
> ++          in >> s; // extract the rest of the word
> ++          yy.from = year(1900);
> ++        }
> ++      else if (int num = 0; in >> num) [[likely]]
> ++        yy.from = year{num};
> ++
> ++      c = ws(in).peek();
> ++      if (c == 'm') // keyword "maximum"
> ++        {
> ++          in >> s; // extract the rest of the word
> ++          yy.to = year::max();
> ++        }
> ++      else if (c == 'o') // keyword "only"
> ++        {
> ++          in >> s; // extract the rest of the word
> ++          yy.to = yy.from;
> +         }
> +       else if (int num = 0; in >> num)
> +-        y.y = year{num};
> ++        yy.to = year{num};
> ++
> +       return in;
> +       }
> +     };
> +
> +-    // As above for minmax_year, but also supports the keyword "only",
> +-    // meaning that the TO year is the same as the FROM year.
> +-    struct minmax_year2
> ++    bool
> ++    select_std_or_dst_abbrev(string& abbrev, minutes save)
> +     {
> +-      minmax_year to;
> +-      year from;
> ++      if (size_t pos = abbrev.find('/'); pos != string::npos)
> ++      {
> ++        // Select one of "STD/DST" for standard or daylight.
> ++        if (save == 0min)
> ++          abbrev.erase(pos);
> ++        else
> ++          abbrev.erase(0, pos + 1);
> ++        return true;
> ++      }
> ++      return false;
> ++    }
> +
> +-      friend istream& operator>>(istream& in, minmax_year2&& y)
> +-      {
> +-      if (ws(in).peek() == 'o') // keyword "only"
> +-        {
> +-          string s;
> +-          in >> s; // extract the whole keyword
> +-          y.to.y = y.from;
> +-        }
> +-      else
> +-        in >> std::move(y.to);
> +-      return in;
> +-      }
> +-    };
> ++    // Set the sys_info::abbrev string by expanding any placeholders.
> ++    void
> ++    format_abbrev_str(sys_info& info, string_view letters = {})
> ++    {
> ++      if (size_t pos = info.abbrev.find('%'); pos != string::npos)
> ++      {
> ++        if (info.abbrev[pos + 1] == 's')
> ++          {
> ++            // Expand "%s" to the variable part, given by Rule::letters.
> ++            if (letters == "-")
> ++              info.abbrev.erase(pos, 2);
> ++            else
> ++              info.abbrev.replace(pos, 2, letters);
> ++          }
> ++        else if (info.abbrev[pos + 1] == 'z')
> ++          {
> ++            // Expand "%z" to the UT offset as +/-hh, +/-hhmm, or
> +/-hhmmss.
> ++            hh_mm_ss<seconds> t(info.offset);
> ++            string z(1, "+-"[t.is_negative()]);
> ++            long val = t.hours().count();
> ++            int digits = 2;
> ++            if (int m = t.minutes().count())
> ++              {
> ++                digits = 4;
> ++                val *= 100;
> ++                val += m;
> ++                if (int s = t.seconds().count())
> ++                  {
> ++                    digits = 6;
> ++                    val *= 100;
> ++                    val += s;
> ++                  }
> ++              }
> ++            auto sval = std::to_string(val);
> ++            z += string(digits - sval.size(), '0');
> ++            z += sval;
> ++            info.abbrev.replace(pos, 2, z);
> ++          }
> ++      }
> ++      else
> ++      select_std_or_dst_abbrev(info.abbrev, info.save);
> ++    }
> +
> +     // A time zone information record.
> +     // Zone  NAME        STDOFF  RULES   FORMAT  [UNTIL]
> +@@ -462,6 +514,7 @@ namespace std::chrono
> +       info.offset = offset();
> +       info.save = minutes(m_save);
> +       info.abbrev = format();
> ++      format_abbrev_str(info); // expand %z
> +       return true;
> +       }
> +
> +@@ -469,12 +522,9 @@ namespace std::chrono
> +       friend class time_zone;
> +
> +       void
> +-      set_abbrev(const string& abbrev)
> ++      set_abbrev(string abbrev)
> +       {
> +-      // In practice, the FORMAT field never needs expanding here.
> +-      if (abbrev.find_first_of("/%") != abbrev.npos)
> +-        __throw_runtime_error("std::chrono::time_zone: invalid data");
> +-      m_buf = abbrev;
> ++      m_buf = std::move(abbrev);
> +       m_pos = 0;
> +       m_expanded = true;
> +       }
> +@@ -544,9 +594,7 @@ namespace std::chrono
> +
> +       // Rule  NAME  FROM  TO  TYPE  IN  ON  AT  SAVE  LETTER/S
> +
> +-      in >> quoted(rule.name)
> +-         >> minmax_year{rule.from}
> +-         >> minmax_year2{rule.to, rule.from};
> ++      in >> quoted(rule.name) >> years_from_to{rule.from, rule.to};
> +
> +       if (char type; in >> type && type != '-')
> +         in.setstate(ios::failbit);
> +@@ -557,7 +605,7 @@ namespace std::chrono
> +       if (save_time.indicator != at_time::Wall)
> +         {
> +           // We don't actually store the save_time.indicator, because we
> +-          // assume that it's always deducable from the actual offset
> value.
> ++          // assume that it's always deducible from the offset value.
> +           auto expected = save_time.time == 0s
> +                             ? at_time::Standard
> +                             : at_time::Daylight;
> +@@ -567,8 +615,6 @@ namespace std::chrono
> +       rule.save = save_time.time;
> +
> +       in >> rule.letters;
> +-      if (rule.letters == "-")
> +-        rule.letters.clear();
> +       return in;
> +       }
> +
> +@@ -719,58 +765,6 @@ namespace std::chrono
> + #endif // TZDB_DISABLED
> +   };
> +
> +-#ifndef TZDB_DISABLED
> +-  namespace
> +-  {
> +-    bool
> +-    select_std_or_dst_abbrev(string& abbrev, minutes save)
> +-    {
> +-      if (size_t pos = abbrev.find('/'); pos != string::npos)
> +-      {
> +-        // Select one of "STD/DST" for standard or daylight.
> +-        if (save == 0min)
> +-          abbrev.erase(pos);
> +-        else
> +-          abbrev.erase(0, pos + 1);
> +-        return true;
> +-      }
> +-      return false;
> +-    }
> +-
> +-    // Set the sys_info::abbrev string by expanding any placeholders.
> +-    void
> +-    format_abbrev_str(sys_info& info, string_view letters = {})
> +-    {
> +-      if (size_t pos = info.abbrev.find("%s"); pos != string::npos)
> +-      {
> +-        // Expand "%s" to the variable part, given by Rule::letters.
> +-        info.abbrev.replace(pos, 2, letters);
> +-      }
> +-      else if (size_t pos = info.abbrev.find("%z"); pos != string::npos)
> +-      {
> +-        // Expand "%z" to the UT offset as +/-hh, +/-hhmm, or +/-hhmmss.
> +-        hh_mm_ss<seconds> t(info.offset);
> +-        string z(1, "+-"[t.is_negative()]);
> +-        long val = t.hours().count();
> +-        if (minutes m = t.minutes(); m != m.zero())
> +-          {
> +-            val *= 100;
> +-            val += m.count();
> +-            if (seconds s = t.seconds(); s != s.zero())
> +-              {
> +-                val *= 100;
> +-                val += s.count();
> +-              }
> +-          }
> +-        z += std::to_string(val);
> +-        info.abbrev.replace(pos, 2, z);
> +-      }
> +-      else
> +-      select_std_or_dst_abbrev(info.abbrev, info.save);
> +-    }
> +-  }
> +-#endif // TZDB_DISABLED
> +-
> +   // Implementation of std::chrono::time_zone::get_info(const
> sys_time<D>&)
> +   sys_info
> +   time_zone::_M_get_sys_info(sys_seconds tp) const
> +@@ -839,12 +833,72 @@ namespace std::chrono
> +     info.abbrev = ri.format();
> +
> +     string_view letters;
> +-    if (i != infos.begin())
> ++    if (i != infos.begin() && i[-1].expanded())
> ++      letters = i[-1].next_letters();
> ++
> ++    if (letters.empty())
> +       {
> +-      if (i[-1].expanded())
> +-        letters = i[-1].next_letters();
> +-      // XXX else need to find Rule active before this time and use it
> +-      // to know the initial offset, save, and letters.
> ++      sys_seconds t = info.begin - seconds(1);
> ++      const year_month_day date(chrono::floor<days>(t));
> ++
> ++      // Try to find a Rule active before this time, to get initial
> ++      // 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.
> ++      const Rule* active_rule = nullptr;
> ++      sys_seconds active_rule_start = sys_seconds::min();
> ++      const Rule* first_std = nullptr;
> ++      for (const auto& rule : rules)
> ++        {
> ++          if (rule.save == minutes(0))
> ++            {
> ++              if (!first_std)
> ++                first_std = &rule;
> ++              else if (rule.from < first_std->from)
> ++                first_std = &rule;
> ++              else if (rule.from == first_std->from)
> ++                {
> ++                  if (rule.start_time(rule.from, {})
> ++                        < first_std->start_time(first_std->from, {}))
> ++                    first_std = &rule;
> ++                }
> ++            }
> ++
> ++          year y = date.year();
> ++
> ++          if (y > rule.to) // rule no longer applies at time t
> ++            continue;
> ++          if (y < rule.from) // rule doesn't apply yet at time t
> ++            continue;
> ++
> ++          sys_seconds rule_start;
> ++
> ++          seconds offset{}; // appropriate for at_time::Universal
> ++          if (rule.when.indicator == at_time::Wall)
> ++            offset = info.offset;
> ++          else if (rule.when.indicator == at_time::Standard)
> ++            offset = ri.offset();
> ++
> ++          // Time the rule takes effect this year:
> ++          rule_start = rule.start_time(y, offset);
> ++
> ++          if (rule_start >= t && rule.from < y)
> ++            {
> ++              // Try this rule in the previous year.
> ++              rule_start = rule.start_time(--y, offset);
> ++            }
> ++
> ++          if (active_rule_start < rule_start && rule_start < t)
> ++            {
> ++              active_rule_start = rule_start;
> ++              active_rule = &rule;
> ++            }
> ++        }
> ++
> ++      if (active_rule)
> ++        letters = active_rule->letters;
> ++      else if (first_std)
> ++        letters = first_std->letters;
> +       }
> +
> +     const Rule* curr_rule = nullptr;
> +@@ -2069,9 +2123,11 @@ namespace std::chrono
> +             istringstream in2(std::move(rules));
> +             in2 >> rules_time;
> +             inf.m_save = duration_cast<minutes>(rules_time.time);
> ++            // If the FORMAT is "STD/DST" then we can choose the right
> one
> ++            // now, so that we store a shorter string.
> +             select_std_or_dst_abbrev(fmt, inf.m_save);
> +           }
> +-        inf.set_abbrev(fmt);
> ++        inf.set_abbrev(std::move(fmt));
> +       }
> +
> +       // YEAR [MONTH [DAY [TIME]]]
> +@@ -2082,7 +2138,12 @@ namespace std::chrono
> +         abbrev_month m{January};
> +         int d = 1;
> +         at_time t{};
> ++        // XXX DAY should support ON format, e.g. lastSun or Sun>=8
> +         in >> m >> d >> t;
> ++        // XXX UNTIL field should be interpreted
> ++        // "using the rules in effect just before the transition"
> ++        // so might need to store as year_month_day and hh_mm_ss and only
> ++        // convert to a sys_time once we know the offset in effect.
> +         inf.m_until = sys_days(year(y)/m.m/day(d)) + seconds(t.time);
> +       }
> +       else
> +diff --git a/libstdc++-v3/testsuite/std/time/time_zone/sys_info_abbrev.cc
> b/libstdc++-v3/testsuite/std/time/time_zone/sys_info_abbrev.cc
> +new file mode 100644
> +index 000000000000..f1a8fff02f58
> +--- /dev/null
> ++++ b/libstdc++-v3/testsuite/std/time/time_zone/sys_info_abbrev.cc
> +@@ -0,0 +1,106 @@
> ++// { 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>
> ++
> ++static bool override_used = false;
> ++
> ++namespace __gnu_cxx
> ++{
> ++  const char* zoneinfo_dir_override() {
> ++    override_used = true;
> ++    return "./";
> ++  }
> ++}
> ++
> ++using namespace std::chrono;
> ++
> ++void
> ++test_format()
> ++{
> ++  std::ofstream("tzdata.zi") << R"(# version test_1
> ++Zone Africa/Bissau -1:2:20 - LMT 1912 Ja 1 1u
> ++                   -1      - %z  1975
> ++                   0       - GMT
> ++Zon Some/Zone 1:2:3   - %z 1900
> ++              1:23:45 - %z 1950
> ++Zo Another/Zone 1:2:3 -     AZ0     1901
> ++                1     Roolz A%sZ    2000
> ++                1     Roolz SAZ/DAZ 2005
> ++                1     Roolz %z
> ++Rule Roolz 1950 max - April 1 2 1 D
> ++Rul  Roolz 1950 max - Oct   1 1 0 S
> ++Z Strange/Zone 1       - X%sX    1980
> ++               1       - FOO/BAR 1990
> ++               2:00    - %zzz    1995
> ++               0:9     - %zzz    1996
> ++               0:8:7   - %zzz    1997
> ++               0:6:5.5 - %zzz    1998
> ++)";
> ++
> ++  const auto& db = reload_tzdb();
> ++  VERIFY( override_used ); // If this fails then XFAIL for the target.
> ++  VERIFY( db.version == "test_1" );
> ++
> ++  // Test formatting %z as
> ++  auto tz = locate_zone("Africa/Bissau");
> ++  auto inf = tz->get_info(sys_days(1974y/1/1));
> ++  VERIFY( inf.abbrev == "-01" );
> ++
> ++  tz = locate_zone("Some/Zone");
> ++  inf = tz->get_info(sys_days(1899y/1/1));
> ++  VERIFY( inf.abbrev == "+010203" );
> ++  inf = tz->get_info(sys_days(1955y/1/1));
> ++  VERIFY( inf.abbrev == "+012345" );
> ++
> ++  tz = locate_zone("Another/Zone");
> ++  // Test formatting %s as the LETTER/S field from the active Rule.
> ++  inf = tz->get_info(sys_days(1910y/January/1));
> ++  VERIFY( inf.abbrev == "ASZ" );
> ++  inf = tz->get_info(sys_days(1950y/January/1));
> ++  VERIFY( inf.abbrev == "ASZ" );
> ++  inf = tz->get_info(sys_days(1950y/June/1));
> ++  VERIFY( inf.abbrev == "ADZ" );
> ++  inf = tz->get_info(sys_days(1999y/January/1));
> ++  VERIFY( inf.abbrev == "ASZ" );
> ++  inf = tz->get_info(sys_days(1999y/July/1));
> ++  VERIFY( inf.abbrev == "ADZ" );
> ++  // Test formatting STD/DST according to the active Rule.
> ++  inf = tz->get_info(sys_days(2000y/January/2));
> ++  VERIFY( inf.abbrev == "SAZ" );
> ++  inf = tz->get_info(sys_days(2001y/January/1));
> ++  VERIFY( inf.abbrev == "SAZ" );
> ++  inf = tz->get_info(sys_days(2001y/July/1));
> ++  VERIFY( inf.abbrev == "DAZ" );
> ++  // Test formatting %z as the offset determined by the active Rule.
> ++  inf = tz->get_info(sys_days(2005y/January/2));
> ++  VERIFY( inf.abbrev == "+01" );
> ++  inf = tz->get_info(sys_days(2006y/January/1));
> ++  VERIFY( inf.abbrev == "+01" );
> ++  inf = tz->get_info(sys_days(2006y/July/1));
> ++  VERIFY( inf.abbrev == "+02" );
> ++
> ++  // Test formatting %z, %s and S/D for a Zone with no associated Rules.
> ++  tz = locate_zone("Strange/Zone");
> ++  inf = tz->get_info(sys_days(1979y/January/1));
> ++  VERIFY( inf.abbrev == "XX" ); // No Rule means nothing to use for %s.
> ++  inf = tz->get_info(sys_days(1981y/July/1));
> ++  VERIFY( inf.abbrev == "FOO" ); // Always standard time means first
> string.
> ++  inf = tz->get_info(sys_days(1994y/July/1));
> ++  VERIFY( inf.abbrev == "+02zz" );
> ++  inf = tz->get_info(sys_days(1995y/July/1));
> ++  VERIFY( inf.abbrev == "+0009zz" );
> ++  inf = tz->get_info(sys_days(1996y/July/1));
> ++  VERIFY( inf.abbrev == "+000807zz" );
> ++  inf = tz->get_info(sys_days(1997y/July/1));
> ++  VERIFY( inf.abbrev == "+000606zz" );
> ++}
> ++
> ++int main()
> ++{
> ++  test_format();
> ++}
> +diff --git a/libstdc++-v3/testsuite/std/time/tzdb/1.cc
> b/libstdc++-v3/testsuite/std/time/tzdb/1.cc
> +index 796f3a8b4256..7a31c1c20ba7 100644
> +--- a/libstdc++-v3/testsuite/std/time/tzdb/1.cc
> ++++ b/libstdc++-v3/testsuite/std/time/tzdb/1.cc
> +@@ -39,11 +39,15 @@ test_locate()
> +   const tzdb& db = get_tzdb();
> +   const time_zone* tz = db.locate_zone("GMT");
> +   VERIFY( tz != nullptr );
> +-  VERIFY( tz->name() == "Etc/GMT" );
> +   VERIFY( tz == std::chrono::locate_zone("GMT") );
> +   VERIFY( tz == db.locate_zone("Etc/GMT") );
> +   VERIFY( tz == db.locate_zone("Etc/GMT+0") );
> +
> ++  // Since 2022f GMT is now a Zone and Etc/GMT a link instead of vice
> versa,
> ++  // but only when using the vanguard format. As of 2024a, the main and
> ++  // rearguard formats still have Etc/GMT as a Zone and GMT as a link.
> ++  VERIFY( tz->name() == "GMT" || tz->name() == "Etc/GMT" );
> ++
> +   VERIFY( db.locate_zone(db.current_zone()->name()) == db.current_zone()
> );
> + }
> +
> +--
> +2.43.5
> +
> --
> 2.47.0
>
>
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> raj.khem@gmail.com]
> -=-=-=-=-=-=-=-=-=-=-=-
>
>

On Thu, Nov 21 2024 at 07:04:06 PM -08:00:00, Khem Raj 
<raj.khem@gmail.com> wrote:
> Patch is fine however I would suggest to remove the hunk changing 
> changellog files it will make it easy to backport

Removed the comments on the changelog from the commit message. but I 
didn't find a hunk that patches Changelog

On Thu, Nov 21, 2024 at 5:35 PM Martin Jansa <martin.jansa@gmail.com> wrote:
>
> Should the backport of tzdata update like
> https://lists.openembedded.org/g/openembedded-core/message/207561
> for scarthgap and
> https://lists.openembedded.org/g/openembedded-core/message/207428
> for styhead be delayed a bit so that this gcc change can go at the same time?

Yes, this makes sense.  I'll keep the tzdata patch in my test queue
but won't merge until I also have the gcc fix.

Markus, could you send versions of this patch for stable branches too?
(styhead, scarthgap, kirkstone)

Thanks!

Steve

>
> I don't know how widespread this is (or what is waybar clock module),
> but the .patch says:
>
> +Since making this change on trunk, the tzdata-2024b release started
> +using %z in the main format, not just vanguard. This makes a backport to
> +release branches necessary (see PR 116657).
>
> +Steve Sakoman
>
> On Fri, Nov 22, 2024 at 2:30 AM Markus Volk via lists.openembedded.org
> <f_l_k=t-online.de@lists.openembedded.org> wrote:
> >
> > There is an issue in the std::chrono::tzdb parser that causes problems
> > since the tzdata-2024b release started using %z in the main format.
> >
> > As a real world problem I encounter an issue with the waybar clock module,
> > which ignores the timezone setting and only shows system time.
> >
> > Signed-off-by: Markus Volk <f_l_k@t-online.de>
> > ---
> >  meta/recipes-devtools/gcc/gcc-14.2.inc        |   1 +
> >  ...4fffe3fc82a710bea66ad651720d71c938b8.patch | 567 ++++++++++++++++++
> >  2 files changed, 568 insertions(+)
> >  create mode 100644 meta/recipes-devtools/gcc/gcc/gcc.git-ab884fffe3fc82a710bea66ad651720d71c938b8.patch
> >
> > diff --git a/meta/recipes-devtools/gcc/gcc-14.2.inc b/meta/recipes-devtools/gcc/gcc-14.2.inc
> > index f05484cfc0..9cfb246294 100644
> > --- a/meta/recipes-devtools/gcc/gcc-14.2.inc
> > +++ b/meta/recipes-devtools/gcc/gcc-14.2.inc
> > @@ -68,6 +68,7 @@ SRC_URI = "${BASEURI} \
> >             file://0023-Fix-install-path-of-linux64.h.patch \
> >             file://0024-Avoid-hardcoded-build-paths-into-ppc-libgcc.patch \
> >             file://0025-gcc-testsuite-tweaks-for-mips-OE.patch \
> > +           file://gcc.git-ab884fffe3fc82a710bea66ad651720d71c938b8.patch \
> >  "
> >
> >  S = "${TMPDIR}/work-shared/gcc-${PV}-${PR}/${SOURCEDIR}"
> > diff --git a/meta/recipes-devtools/gcc/gcc/gcc.git-ab884fffe3fc82a710bea66ad651720d71c938b8.patch b/meta/recipes-devtools/gcc/gcc/gcc.git-ab884fffe3fc82a710bea66ad651720d71c938b8.patch
> > new file mode 100644
> > index 0000000000..ca6fc92e07
> > --- /dev/null
> > +++ b/meta/recipes-devtools/gcc/gcc/gcc.git-ab884fffe3fc82a710bea66ad651720d71c938b8.patch
> > @@ -0,0 +1,567 @@
> > +From ab884fffe3fc82a710bea66ad651720d71c938b8 Mon Sep 17 00:00:00 2001
> > +From: Jonathan Wakely <jwakely@redhat.com>
> > +Date: Tue, 30 Apr 2024 09:52:13 +0100
> > +Subject: [PATCH] libstdc++: Fix std::chrono::tzdb to work with vanguard format
> > +
> > +I found some issues in the std::chrono::tzdb parser by testing the
> > +tzdata "vanguard" format, which uses new features that aren't enabled in
> > +the "main" and "rearguard" data formats.
> > +
> > +Since 2024a the keyword "minimum" is no longer valid for the FROM and TO
> > +fields in a Rule line, which means that "m" is now a valid abbreviation
> > +for "maximum". Previously we expected either "mi" or "ma". For backwards
> > +compatibility, a FROM field beginning with "mi" is still supported and
> > +is treated as 1900. The "maximum" keyword is only allowed in TO now,
> > +because it makes no sense in FROM. To support these changes the
> > +minmax_year and minmax_year2 classes for parsing FROM and TO are
> > +replaced with a single years_from_to class that reads both fields.
> > +
> > +The vanguard format makes use of %z in Zone FORMAT fields, which caused
> > +an exception to be thrown from ZoneInfo::set_abbrev because no % or /
> > +characters were expected when a Zone doesn't use a named Rule. The
> > +ZoneInfo::to(sys_info&) function now uses format_abbrev_str to replace
> > +any %z with the current offset. Although format_abbrev_str also checks
> > +for %s and STD/DST formats, those only make sense when a named Rule is
> > +in effect, so won't occur when ZoneInfo::to(sys_info&) is used.
> > +
> > +Since making this change on trunk, the tzdata-2024b release started
> > +using %z in the main format, not just vanguard. This makes a backport to
> > +release branches necessary (see PR 116657).
> > +
> > +This change also implements a feature that has always been missing from
> > +time_zone::_M_get_sys_info: finding the Rule that is active before the
> > +specified time point, so that we can correctly handle %s in the FORMAT
> > +for the first new sys_info that gets created. This requires implementing
> > +a poorly documented feature of zic, to get the LETTERS field from a
> > +later transition, as described at
> > +https://mm.icann.org/pipermail/tz/2024-April/058891.html
> > +In order for this to work we need to be able to distinguish an empty
> > +letters field (as used by CE%sT where the variable part is either empty
> > +or "S") from "the letters field is not known for this transition". The
> > +tzdata file uses "-" for an empty letters field, which libstdc++ was
> > +previously replacing with "" when the Rule was parsed. Instead, we now
> > +preserve the "-" in the Rule object, so that "" can be used for the case
> > +where we don't know the letters (and so need to decide it).
> > +
> > +libstdc++-v3/ChangeLog:
> > +
> > +       * src/c++20/tzdb.cc (minmax_year, minmax_year2): Remove.
> > +       (years_from_to): New class replacing minmax_year and
> > +       minmax_year2.
> > +       (format_abbrev_str, select_std_or_dst_abbrev): Move earlier in
> > +       the file. Handle "-" for letters.
> > +       (ZoneInfo::to): Use format_abbrev_str to expand %z.
> > +       (ZoneInfo::set_abbrev): Remove exception. Change parameter from
> > +       reference to value.
> > +       (operator>>(istream&, Rule&)): Do not clear letters when it
> > +       contains "-".
> > +       (time_zone::_M_get_sys_info): Add missing logic to find the Rule
> > +       in effect before the time point.
> > +       * testsuite/std/time/tzdb/1.cc: Adjust for vanguard format using
> > +       "GMT" as the Zone name, not as a Link to "Etc/GMT".
> > +       * testsuite/std/time/time_zone/sys_info_abbrev.cc: New test.
> > +
> > +(cherry picked from commit 0ca8d56f2085715f27ee536c6c344bc47af49cdd)
> > +
> > +Upstream-Status: Backport [https://gcc.gnu.org/git/gitweb.cgi?p=gcc.git;h=5ceea2ac106d6dd1aa8175670b15a801316cf1c9]
> > +
> > +Signed-off-by: Markus Volk <f_l_k@t-online.de>
> > +---
> > + libstdc++-v3/src/c++20/tzdb.cc                | 265 +++++++++++-------
> > + .../std/time/time_zone/sys_info_abbrev.cc     | 106 +++++++
> > + libstdc++-v3/testsuite/std/time/tzdb/1.cc     |   6 +-
> > + 3 files changed, 274 insertions(+), 103 deletions(-)
> > + create mode 100644 libstdc++-v3/testsuite/std/time/time_zone/sys_info_abbrev.cc
> > +
> > +diff --git a/libstdc++-v3/src/c++20/tzdb.cc b/libstdc++-v3/src/c++20/tzdb.cc
> > +index c7c7cc9deee6..7e8cce7ce8cf 100644
> > +--- a/libstdc++-v3/src/c++20/tzdb.cc
> > ++++ b/libstdc++-v3/src/c++20/tzdb.cc
> > +@@ -342,51 +342,103 @@ namespace std::chrono
> > +       friend istream& operator>>(istream&, on_day&);
> > +     };
> > +
> > +-    // Wrapper for chrono::year that reads a year, or one of the keywords
> > +-    // "minimum" or "maximum", or an unambiguous prefix of a keyword.
> > +-    struct minmax_year
> > ++    // Wrapper for two chrono::year values, which reads the FROM and TO
> > ++    // fields of a Rule line. The FROM field is a year and TO is a year or
> > ++    // one of the keywords "maximum" or "only" (or an abbreviation of those).
> > ++    // For backwards compatibility, the keyword "minimum" is recognized
> > ++    // for FROM and interpreted as 1900.
> > ++    struct years_from_to
> > +     {
> > +-      year& y;
> > ++      year& from;
> > ++      year& to;
> > +
> > +-      friend istream& operator>>(istream& in, minmax_year&& y)
> > ++      friend istream& operator>>(istream& in, years_from_to&& yy)
> > +       {
> > +-      if (ws(in).peek() == 'm') // keywords "minimum" or "maximum"
> > ++      string s;
> > ++      auto c = ws(in).peek();
> > ++      if (c == 'm') [[unlikely]] // keyword "minimum"
> > +         {
> > +-          string s;
> > +-          in >> s; // extract the rest of the word, but only look at s[1]
> > +-          if (s[1] == 'a')
> > +-            y.y = year::max();
> > +-          else if (s[1] == 'i')
> > +-            y.y = year::min();
> > +-          else
> > +-            in.setstate(ios::failbit);
> > ++          in >> s; // extract the rest of the word
> > ++          yy.from = year(1900);
> > ++        }
> > ++      else if (int num = 0; in >> num) [[likely]]
> > ++        yy.from = year{num};
> > ++
> > ++      c = ws(in).peek();
> > ++      if (c == 'm') // keyword "maximum"
> > ++        {
> > ++          in >> s; // extract the rest of the word
> > ++          yy.to = year::max();
> > ++        }
> > ++      else if (c == 'o') // keyword "only"
> > ++        {
> > ++          in >> s; // extract the rest of the word
> > ++          yy.to = yy.from;
> > +         }
> > +       else if (int num = 0; in >> num)
> > +-        y.y = year{num};
> > ++        yy.to = year{num};
> > ++
> > +       return in;
> > +       }
> > +     };
> > +
> > +-    // As above for minmax_year, but also supports the keyword "only",
> > +-    // meaning that the TO year is the same as the FROM year.
> > +-    struct minmax_year2
> > ++    bool
> > ++    select_std_or_dst_abbrev(string& abbrev, minutes save)
> > +     {
> > +-      minmax_year to;
> > +-      year from;
> > ++      if (size_t pos = abbrev.find('/'); pos != string::npos)
> > ++      {
> > ++        // Select one of "STD/DST" for standard or daylight.
> > ++        if (save == 0min)
> > ++          abbrev.erase(pos);
> > ++        else
> > ++          abbrev.erase(0, pos + 1);
> > ++        return true;
> > ++      }
> > ++      return false;
> > ++    }
> > +
> > +-      friend istream& operator>>(istream& in, minmax_year2&& y)
> > +-      {
> > +-      if (ws(in).peek() == 'o') // keyword "only"
> > +-        {
> > +-          string s;
> > +-          in >> s; // extract the whole keyword
> > +-          y.to.y = y.from;
> > +-        }
> > +-      else
> > +-        in >> std::move(y.to);
> > +-      return in;
> > +-      }
> > +-    };
> > ++    // Set the sys_info::abbrev string by expanding any placeholders.
> > ++    void
> > ++    format_abbrev_str(sys_info& info, string_view letters = {})
> > ++    {
> > ++      if (size_t pos = info.abbrev.find('%'); pos != string::npos)
> > ++      {
> > ++        if (info.abbrev[pos + 1] == 's')
> > ++          {
> > ++            // Expand "%s" to the variable part, given by Rule::letters.
> > ++            if (letters == "-")
> > ++              info.abbrev.erase(pos, 2);
> > ++            else
> > ++              info.abbrev.replace(pos, 2, letters);
> > ++          }
> > ++        else if (info.abbrev[pos + 1] == 'z')
> > ++          {
> > ++            // Expand "%z" to the UT offset as +/-hh, +/-hhmm, or +/-hhmmss.
> > ++            hh_mm_ss<seconds> t(info.offset);
> > ++            string z(1, "+-"[t.is_negative()]);
> > ++            long val = t.hours().count();
> > ++            int digits = 2;
> > ++            if (int m = t.minutes().count())
> > ++              {
> > ++                digits = 4;
> > ++                val *= 100;
> > ++                val += m;
> > ++                if (int s = t.seconds().count())
> > ++                  {
> > ++                    digits = 6;
> > ++                    val *= 100;
> > ++                    val += s;
> > ++                  }
> > ++              }
> > ++            auto sval = std::to_string(val);
> > ++            z += string(digits - sval.size(), '0');
> > ++            z += sval;
> > ++            info.abbrev.replace(pos, 2, z);
> > ++          }
> > ++      }
> > ++      else
> > ++      select_std_or_dst_abbrev(info.abbrev, info.save);
> > ++    }
> > +
> > +     // A time zone information record.
> > +     // Zone  NAME        STDOFF  RULES   FORMAT  [UNTIL]
> > +@@ -462,6 +514,7 @@ namespace std::chrono
> > +       info.offset = offset();
> > +       info.save = minutes(m_save);
> > +       info.abbrev = format();
> > ++      format_abbrev_str(info); // expand %z
> > +       return true;
> > +       }
> > +
> > +@@ -469,12 +522,9 @@ namespace std::chrono
> > +       friend class time_zone;
> > +
> > +       void
> > +-      set_abbrev(const string& abbrev)
> > ++      set_abbrev(string abbrev)
> > +       {
> > +-      // In practice, the FORMAT field never needs expanding here.
> > +-      if (abbrev.find_first_of("/%") != abbrev.npos)
> > +-        __throw_runtime_error("std::chrono::time_zone: invalid data");
> > +-      m_buf = abbrev;
> > ++      m_buf = std::move(abbrev);
> > +       m_pos = 0;
> > +       m_expanded = true;
> > +       }
> > +@@ -544,9 +594,7 @@ namespace std::chrono
> > +
> > +       // Rule  NAME  FROM  TO  TYPE  IN  ON  AT  SAVE  LETTER/S
> > +
> > +-      in >> quoted(rule.name)
> > +-         >> minmax_year{rule.from}
> > +-         >> minmax_year2{rule.to, rule.from};
> > ++      in >> quoted(rule.name) >> years_from_to{rule.from, rule.to};
> > +
> > +       if (char type; in >> type && type != '-')
> > +         in.setstate(ios::failbit);
> > +@@ -557,7 +605,7 @@ namespace std::chrono
> > +       if (save_time.indicator != at_time::Wall)
> > +         {
> > +           // We don't actually store the save_time.indicator, because we
> > +-          // assume that it's always deducable from the actual offset value.
> > ++          // assume that it's always deducible from the offset value.
> > +           auto expected = save_time.time == 0s
> > +                             ? at_time::Standard
> > +                             : at_time::Daylight;
> > +@@ -567,8 +615,6 @@ namespace std::chrono
> > +       rule.save = save_time.time;
> > +
> > +       in >> rule.letters;
> > +-      if (rule.letters == "-")
> > +-        rule.letters.clear();
> > +       return in;
> > +       }
> > +
> > +@@ -719,58 +765,6 @@ namespace std::chrono
> > + #endif // TZDB_DISABLED
> > +   };
> > +
> > +-#ifndef TZDB_DISABLED
> > +-  namespace
> > +-  {
> > +-    bool
> > +-    select_std_or_dst_abbrev(string& abbrev, minutes save)
> > +-    {
> > +-      if (size_t pos = abbrev.find('/'); pos != string::npos)
> > +-      {
> > +-        // Select one of "STD/DST" for standard or daylight.
> > +-        if (save == 0min)
> > +-          abbrev.erase(pos);
> > +-        else
> > +-          abbrev.erase(0, pos + 1);
> > +-        return true;
> > +-      }
> > +-      return false;
> > +-    }
> > +-
> > +-    // Set the sys_info::abbrev string by expanding any placeholders.
> > +-    void
> > +-    format_abbrev_str(sys_info& info, string_view letters = {})
> > +-    {
> > +-      if (size_t pos = info.abbrev.find("%s"); pos != string::npos)
> > +-      {
> > +-        // Expand "%s" to the variable part, given by Rule::letters.
> > +-        info.abbrev.replace(pos, 2, letters);
> > +-      }
> > +-      else if (size_t pos = info.abbrev.find("%z"); pos != string::npos)
> > +-      {
> > +-        // Expand "%z" to the UT offset as +/-hh, +/-hhmm, or +/-hhmmss.
> > +-        hh_mm_ss<seconds> t(info.offset);
> > +-        string z(1, "+-"[t.is_negative()]);
> > +-        long val = t.hours().count();
> > +-        if (minutes m = t.minutes(); m != m.zero())
> > +-          {
> > +-            val *= 100;
> > +-            val += m.count();
> > +-            if (seconds s = t.seconds(); s != s.zero())
> > +-              {
> > +-                val *= 100;
> > +-                val += s.count();
> > +-              }
> > +-          }
> > +-        z += std::to_string(val);
> > +-        info.abbrev.replace(pos, 2, z);
> > +-      }
> > +-      else
> > +-      select_std_or_dst_abbrev(info.abbrev, info.save);
> > +-    }
> > +-  }
> > +-#endif // TZDB_DISABLED
> > +-
> > +   // Implementation of std::chrono::time_zone::get_info(const sys_time<D>&)
> > +   sys_info
> > +   time_zone::_M_get_sys_info(sys_seconds tp) const
> > +@@ -839,12 +833,72 @@ namespace std::chrono
> > +     info.abbrev = ri.format();
> > +
> > +     string_view letters;
> > +-    if (i != infos.begin())
> > ++    if (i != infos.begin() && i[-1].expanded())
> > ++      letters = i[-1].next_letters();
> > ++
> > ++    if (letters.empty())
> > +       {
> > +-      if (i[-1].expanded())
> > +-        letters = i[-1].next_letters();
> > +-      // XXX else need to find Rule active before this time and use it
> > +-      // to know the initial offset, save, and letters.
> > ++      sys_seconds t = info.begin - seconds(1);
> > ++      const year_month_day date(chrono::floor<days>(t));
> > ++
> > ++      // Try to find a Rule active before this time, to get initial
> > ++      // 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.
> > ++      const Rule* active_rule = nullptr;
> > ++      sys_seconds active_rule_start = sys_seconds::min();
> > ++      const Rule* first_std = nullptr;
> > ++      for (const auto& rule : rules)
> > ++        {
> > ++          if (rule.save == minutes(0))
> > ++            {
> > ++              if (!first_std)
> > ++                first_std = &rule;
> > ++              else if (rule.from < first_std->from)
> > ++                first_std = &rule;
> > ++              else if (rule.from == first_std->from)
> > ++                {
> > ++                  if (rule.start_time(rule.from, {})
> > ++                        < first_std->start_time(first_std->from, {}))
> > ++                    first_std = &rule;
> > ++                }
> > ++            }
> > ++
> > ++          year y = date.year();
> > ++
> > ++          if (y > rule.to) // rule no longer applies at time t
> > ++            continue;
> > ++          if (y < rule.from) // rule doesn't apply yet at time t
> > ++            continue;
> > ++
> > ++          sys_seconds rule_start;
> > ++
> > ++          seconds offset{}; // appropriate for at_time::Universal
> > ++          if (rule.when.indicator == at_time::Wall)
> > ++            offset = info.offset;
> > ++          else if (rule.when.indicator == at_time::Standard)
> > ++            offset = ri.offset();
> > ++
> > ++          // Time the rule takes effect this year:
> > ++          rule_start = rule.start_time(y, offset);
> > ++
> > ++          if (rule_start >= t && rule.from < y)
> > ++            {
> > ++              // Try this rule in the previous year.
> > ++              rule_start = rule.start_time(--y, offset);
> > ++            }
> > ++
> > ++          if (active_rule_start < rule_start && rule_start < t)
> > ++            {
> > ++              active_rule_start = rule_start;
> > ++              active_rule = &rule;
> > ++            }
> > ++        }
> > ++
> > ++      if (active_rule)
> > ++        letters = active_rule->letters;
> > ++      else if (first_std)
> > ++        letters = first_std->letters;
> > +       }
> > +
> > +     const Rule* curr_rule = nullptr;
> > +@@ -2069,9 +2123,11 @@ namespace std::chrono
> > +             istringstream in2(std::move(rules));
> > +             in2 >> rules_time;
> > +             inf.m_save = duration_cast<minutes>(rules_time.time);
> > ++            // If the FORMAT is "STD/DST" then we can choose the right one
> > ++            // now, so that we store a shorter string.
> > +             select_std_or_dst_abbrev(fmt, inf.m_save);
> > +           }
> > +-        inf.set_abbrev(fmt);
> > ++        inf.set_abbrev(std::move(fmt));
> > +       }
> > +
> > +       // YEAR [MONTH [DAY [TIME]]]
> > +@@ -2082,7 +2138,12 @@ namespace std::chrono
> > +         abbrev_month m{January};
> > +         int d = 1;
> > +         at_time t{};
> > ++        // XXX DAY should support ON format, e.g. lastSun or Sun>=8
> > +         in >> m >> d >> t;
> > ++        // XXX UNTIL field should be interpreted
> > ++        // "using the rules in effect just before the transition"
> > ++        // so might need to store as year_month_day and hh_mm_ss and only
> > ++        // convert to a sys_time once we know the offset in effect.
> > +         inf.m_until = sys_days(year(y)/m.m/day(d)) + seconds(t.time);
> > +       }
> > +       else
> > +diff --git a/libstdc++-v3/testsuite/std/time/time_zone/sys_info_abbrev.cc b/libstdc++-v3/testsuite/std/time/time_zone/sys_info_abbrev.cc
> > +new file mode 100644
> > +index 000000000000..f1a8fff02f58
> > +--- /dev/null
> > ++++ b/libstdc++-v3/testsuite/std/time/time_zone/sys_info_abbrev.cc
> > +@@ -0,0 +1,106 @@
> > ++// { 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>
> > ++
> > ++static bool override_used = false;
> > ++
> > ++namespace __gnu_cxx
> > ++{
> > ++  const char* zoneinfo_dir_override() {
> > ++    override_used = true;
> > ++    return "./";
> > ++  }
> > ++}
> > ++
> > ++using namespace std::chrono;
> > ++
> > ++void
> > ++test_format()
> > ++{
> > ++  std::ofstream("tzdata.zi") << R"(# version test_1
> > ++Zone Africa/Bissau -1:2:20 - LMT 1912 Ja 1 1u
> > ++                   -1      - %z  1975
> > ++                   0       - GMT
> > ++Zon Some/Zone 1:2:3   - %z 1900
> > ++              1:23:45 - %z 1950
> > ++Zo Another/Zone 1:2:3 -     AZ0     1901
> > ++                1     Roolz A%sZ    2000
> > ++                1     Roolz SAZ/DAZ 2005
> > ++                1     Roolz %z
> > ++Rule Roolz 1950 max - April 1 2 1 D
> > ++Rul  Roolz 1950 max - Oct   1 1 0 S
> > ++Z Strange/Zone 1       - X%sX    1980
> > ++               1       - FOO/BAR 1990
> > ++               2:00    - %zzz    1995
> > ++               0:9     - %zzz    1996
> > ++               0:8:7   - %zzz    1997
> > ++               0:6:5.5 - %zzz    1998
> > ++)";
> > ++
> > ++  const auto& db = reload_tzdb();
> > ++  VERIFY( override_used ); // If this fails then XFAIL for the target.
> > ++  VERIFY( db.version == "test_1" );
> > ++
> > ++  // Test formatting %z as
> > ++  auto tz = locate_zone("Africa/Bissau");
> > ++  auto inf = tz->get_info(sys_days(1974y/1/1));
> > ++  VERIFY( inf.abbrev == "-01" );
> > ++
> > ++  tz = locate_zone("Some/Zone");
> > ++  inf = tz->get_info(sys_days(1899y/1/1));
> > ++  VERIFY( inf.abbrev == "+010203" );
> > ++  inf = tz->get_info(sys_days(1955y/1/1));
> > ++  VERIFY( inf.abbrev == "+012345" );
> > ++
> > ++  tz = locate_zone("Another/Zone");
> > ++  // Test formatting %s as the LETTER/S field from the active Rule.
> > ++  inf = tz->get_info(sys_days(1910y/January/1));
> > ++  VERIFY( inf.abbrev == "ASZ" );
> > ++  inf = tz->get_info(sys_days(1950y/January/1));
> > ++  VERIFY( inf.abbrev == "ASZ" );
> > ++  inf = tz->get_info(sys_days(1950y/June/1));
> > ++  VERIFY( inf.abbrev == "ADZ" );
> > ++  inf = tz->get_info(sys_days(1999y/January/1));
> > ++  VERIFY( inf.abbrev == "ASZ" );
> > ++  inf = tz->get_info(sys_days(1999y/July/1));
> > ++  VERIFY( inf.abbrev == "ADZ" );
> > ++  // Test formatting STD/DST according to the active Rule.
> > ++  inf = tz->get_info(sys_days(2000y/January/2));
> > ++  VERIFY( inf.abbrev == "SAZ" );
> > ++  inf = tz->get_info(sys_days(2001y/January/1));
> > ++  VERIFY( inf.abbrev == "SAZ" );
> > ++  inf = tz->get_info(sys_days(2001y/July/1));
> > ++  VERIFY( inf.abbrev == "DAZ" );
> > ++  // Test formatting %z as the offset determined by the active Rule.
> > ++  inf = tz->get_info(sys_days(2005y/January/2));
> > ++  VERIFY( inf.abbrev == "+01" );
> > ++  inf = tz->get_info(sys_days(2006y/January/1));
> > ++  VERIFY( inf.abbrev == "+01" );
> > ++  inf = tz->get_info(sys_days(2006y/July/1));
> > ++  VERIFY( inf.abbrev == "+02" );
> > ++
> > ++  // Test formatting %z, %s and S/D for a Zone with no associated Rules.
> > ++  tz = locate_zone("Strange/Zone");
> > ++  inf = tz->get_info(sys_days(1979y/January/1));
> > ++  VERIFY( inf.abbrev == "XX" ); // No Rule means nothing to use for %s.
> > ++  inf = tz->get_info(sys_days(1981y/July/1));
> > ++  VERIFY( inf.abbrev == "FOO" ); // Always standard time means first string.
> > ++  inf = tz->get_info(sys_days(1994y/July/1));
> > ++  VERIFY( inf.abbrev == "+02zz" );
> > ++  inf = tz->get_info(sys_days(1995y/July/1));
> > ++  VERIFY( inf.abbrev == "+0009zz" );
> > ++  inf = tz->get_info(sys_days(1996y/July/1));
> > ++  VERIFY( inf.abbrev == "+000807zz" );
> > ++  inf = tz->get_info(sys_days(1997y/July/1));
> > ++  VERIFY( inf.abbrev == "+000606zz" );
> > ++}
> > ++
> > ++int main()
> > ++{
> > ++  test_format();
> > ++}
> > +diff --git a/libstdc++-v3/testsuite/std/time/tzdb/1.cc b/libstdc++-v3/testsuite/std/time/tzdb/1.cc
> > +index 796f3a8b4256..7a31c1c20ba7 100644
> > +--- a/libstdc++-v3/testsuite/std/time/tzdb/1.cc
> > ++++ b/libstdc++-v3/testsuite/std/time/tzdb/1.cc
> > +@@ -39,11 +39,15 @@ test_locate()
> > +   const tzdb& db = get_tzdb();
> > +   const time_zone* tz = db.locate_zone("GMT");
> > +   VERIFY( tz != nullptr );
> > +-  VERIFY( tz->name() == "Etc/GMT" );
> > +   VERIFY( tz == std::chrono::locate_zone("GMT") );
> > +   VERIFY( tz == db.locate_zone("Etc/GMT") );
> > +   VERIFY( tz == db.locate_zone("Etc/GMT+0") );
> > +
> > ++  // Since 2022f GMT is now a Zone and Etc/GMT a link instead of vice versa,
> > ++  // but only when using the vanguard format. As of 2024a, the main and
> > ++  // rearguard formats still have Etc/GMT as a Zone and GMT as a link.
> > ++  VERIFY( tz->name() == "GMT" || tz->name() == "Etc/GMT" );
> > ++
> > +   VERIFY( db.locate_zone(db.current_zone()->name()) == db.current_zone() );
> > + }
> > +
> > +--
> > +2.43.5
> > +
> > --
> > 2.47.0
> >
> >
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> >