https://gcc.gnu.org/g:864f26bd7548d1a290b334b8f5375199449fcff5
commit r17-484-g864f26bd7548d1a290b334b8f5375199449fcff5 Author: Álvaro Begué <[email protected]> Date: Sun Apr 26 19:51:17 2026 -0400 libstdc++: Fix numeric save offset on Zone lines [PR124851] When a Zone line specifies a numeric value as its RULES field (the constant DST save value for that zone line, e.g. Africa/Gaborone's "2 1 CAST" line), the parser stored the standard offset alone in ZoneInfo::m_offset. ZoneInfo::to() then returned that as sys_info::offset, dropping the numeric save and reporting a total offset that was wrong by the save amount. This was inconsistent with the two ZoneInfo constructors that take a sys_info, which previously stored the *total* offset (stdoff + save) in m_offset. As a result m_offset's semantics depended on which code path created the ZoneInfo, and only the parser path's lines with non-zero numeric save were observably broken. Fix by giving m_offset a single semantics: always the standard offset only. The two sys_info-taking constructors now subtract the save before storing, and to(0 adds it back when reconstructing the sys_info. The remaining .offset() callers inside _M_get_sys_info already expect the standard offset (they are computing rule firing times, where the save component is added separately from the active rule's save value), so no other call sites need adjustment. libstdc++-v3/ChangeLog: PR libstdc++/124851 * src/c++20/tzdb.cc (ZoneInfo::ZoneInfo(sys_info&&)): Store stdoff only in m_offset (subtract info.save). (ZoneInfo::ZoneInfo(const pair<sys_info, string_view>&)): Likewise. (ZoneInfo::offset()): Document new semantics. (ZoneInfo::to(sys_info&)): Add m_save back to offset() when populating sys_info::offset. * testsuite/std/time/time_zone/numeric_save.cc: New test. Reviewed-by: Jonathan Wakely <[email protected]> Reviewed-by: Tomasz Kamiński <[email protected]> Signed-off-by: Álvaro Begué <[email protected]> Diff: --- libstdc++-v3/src/c++20/tzdb.cc | 11 ++-- .../testsuite/std/time/time_zone/numeric_save.cc | 58 ++++++++++++++++++++++ 2 files changed, 64 insertions(+), 5 deletions(-) diff --git a/libstdc++-v3/src/c++20/tzdb.cc b/libstdc++-v3/src/c++20/tzdb.cc index 587e88bc0dd5..886d7e71d8eb 100644 --- a/libstdc++-v3/src/c++20/tzdb.cc +++ b/libstdc++-v3/src/c++20/tzdb.cc @@ -482,12 +482,13 @@ namespace std::chrono ZoneInfo(sys_info&& info) : m_buf(std::move(info.abbrev)), m_expanded(true), m_save(info.save), - m_offset(info.offset), m_until(info.end) + m_offset(info.offset - seconds(info.save)), m_until(info.end) { } ZoneInfo(const pair<sys_info, string_view>& info) - : m_expanded(true), m_save(info.first.save), m_offset(info.first.offset), - m_until(info.first.end) + : m_expanded(true), m_save(info.first.save), + m_offset(info.first.offset - seconds(info.first.save)), + m_until(info.first.end) { if (info.second.size()) { @@ -498,7 +499,7 @@ namespace std::chrono m_buf += info.first.abbrev; } - // STDOFF: Seconds from UTC during standard time. + // STDOFF: Seconds from UTC during standard time (without any save). seconds offset() const noexcept { return m_offset; } @@ -543,7 +544,7 @@ namespace std::chrono return false; info.end = until(); - info.offset = offset(); + info.offset = offset() + seconds(m_save); info.save = minutes(m_save); info.abbrev = format(); format_abbrev_str(info); // expand %z diff --git a/libstdc++-v3/testsuite/std/time/time_zone/numeric_save.cc b/libstdc++-v3/testsuite/std/time/time_zone/numeric_save.cc new file mode 100644 index 000000000000..687524bb355b --- /dev/null +++ b/libstdc++-v3/testsuite/std/time/time_zone/numeric_save.cc @@ -0,0 +1,58 @@ +// { 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* } } + +// When a Zone line specifies a numeric value as its RULES field, that +// value is the constant DST save value for that zone line. Per +// [time.zone.info.sys] sys_info::offset is the total UTC offset +// (stdoff + save). + +#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 "./"; + } +} + +int +main() +{ + using namespace std::chrono; + + std::ofstream("tzdata.zi") << R"(# version test_numeric_save +Z Test/Gaborone 2 - CAT 1943 Sep 19 2 + 2 1 CAST 1944 Mar 19 2 + 2 - CAT +)"; + + const auto& db = reload_tzdb(); + VERIFY( override_used ); // If this fails then XFAIL for the target. + VERIFY( db.version == "test_numeric_save" ); + + auto* tz = locate_zone("Test/Gaborone"); + + // Sample well inside the CAST (numeric-save) zone line. + auto info = tz->get_info(sys_days(1943y/December/15)); + VERIFY( info.offset == 3h ); // stdoff +2h + save +1h + VERIFY( info.save == 60min ); + VERIFY( info.abbrev == "CAST" ); + + // Bordering zone lines should report the standard offset with save 0. + auto before = tz->get_info(sys_days(1943y/September/1)); + VERIFY( before.offset == 2h ); + VERIFY( before.save == 0min ); + VERIFY( before.abbrev == "CAT" ); + + auto after = tz->get_info(sys_days(1944y/April/15)); + VERIFY( after.offset == 2h ); + VERIFY( after.save == 0min ); + VERIFY( after.abbrev == "CAT" ); +}
