{"id":2228544,"url":"http://patchwork.ozlabs.org/api/1.2/patches/2228544/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/patch/CAF8dVMUqfv+ggKjr2N=NAefWYgo4BK8Bb=wMS_b5DNqtkmK-Tw@mail.gmail.com/","project":{"id":17,"url":"http://patchwork.ozlabs.org/api/1.2/projects/17/?format=json","name":"GNU Compiler Collection","link_name":"gcc","list_id":"gcc-patches.gcc.gnu.org","list_email":"gcc-patches@gcc.gnu.org","web_url":null,"scm_url":null,"webscm_url":null,"list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"","list_archive_url":null,"date":"2026-04-26T23:51:17","name":"[v2,1/5] libstdc++: Fix numeric save offset on Zone lines [PR124851]","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"d254f2cba69b28b5ec64431a7cfdabccf8de5476","submitter":{"id":93119,"url":"http://patchwork.ozlabs.org/api/1.2/people/93119/?format=json","name":"Álvaro Begué","email":"alvaro.begue@gmail.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/gcc/patch/CAF8dVMUqfv+ggKjr2N=NAefWYgo4BK8Bb=wMS_b5DNqtkmK-Tw@mail.gmail.com/mbox/","series":[{"id":501555,"url":"http://patchwork.ozlabs.org/api/1.2/series/501555/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/list/?series=501555","date":"2026-04-26T23:42:54","name":"libstdc++: chrono tzdb correctness fixes","version":2,"mbox":"http://patchwork.ozlabs.org/series/501555/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2228544/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2228544/checks/","tags":{},"related":[],"headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","gcc-patches@gcc.gnu.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","gcc-patches@gcc.gnu.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=ioevyv5s;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org\n (client-ip=2620:52:6:3111::32; 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Sun, 26 Apr 2026\n 16:51:53 -0700 (PDT)","MIME-Version":"1.0","From":"=?utf-8?b?w4FsdmFybyBCZWd1w6k=?= ","Date":"Sun, 26 Apr 2026 19:51:17 -0400","X-Gm-Features":"AVHnY4IMsCUp2tP-IzTVON7qfBTKmxb7tLdgXHnEsuMGulPW-T-SQpDKUofCr28","Message-ID":"\n ","Subject":"[PATCH v2 1/5] libstdc++: Fix numeric save offset on Zone lines\n [PR124851]","To":"gcc-patches@gcc.gnu.org","Cc":"jwakely@redhat.com, libstdc++@gcc.gnu.org, tkaminsk@redhat.com,\n\t=?utf-8?b?w4FsdmFybyBCZWd1w6k=?= ","Content-Type":"multipart/alternative; boundary=\"000000000000b5abcc065065aedc\"","X-BeenThere":"gcc-patches@gcc.gnu.org","X-Mailman-Version":"2.1.30","Precedence":"list","List-Id":"Gcc-patches mailing list ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org"},"content":"When a Zone line specifies a numeric value as its RULES field (the\nconstant DST save value for that zone line, e.g. Africa/Gaborone's\n\"2 1 CAST\" line), the parser stored the standard offset alone in\nZoneInfo::m_offset. ZoneInfo::to() then returned that as\nsys_info::offset, dropping the numeric save and reporting a total\noffset that was wrong by the save amount.\n\nThis was inconsistent with the two ZoneInfo constructors that take a\nsys_info, which previously stored the *total* offset (stdoff + save) in\nm_offset. As a result m_offset's semantics depended on which code path\ncreated the ZoneInfo, and only the parser path's lines with non-zero\nnumeric save were observably broken.\n\nFix by giving m_offset a single semantics: always the standard offset\nonly. The two sys_info-taking constructors now subtract the save before\nstoring, and to() adds it back when reconstructing the sys_info.\n\nThe remaining .offset() callers inside _M_get_sys_info already expect\nthe standard offset (they are computing rule firing times, where the\nsave component is added separately from the active rule's save value),\nso no other call sites need adjustment.\n\nlibstdc++-v3/ChangeLog:\n\nPR libstdc++/124851\n* src/c++20/tzdb.cc (ZoneInfo::ZoneInfo(sys_info&&)): Store\nstdoff only in m_offset (subtract info.save).\n(ZoneInfo::ZoneInfo(const pair&)):\nLikewise.\n(ZoneInfo::offset()): Document new semantics.\n(ZoneInfo::to(sys_info&)): Add m_save back to offset() when\npopulating sys_info::offset.\n* testsuite/std/time/time_zone/numeric_save.cc: New test.\n\nSigned-off-by: Álvaro Begué \n---\n libstdc++-v3/src/c++20/tzdb.cc | 9 +--\n .../std/time/time_zone/numeric_save.cc | 58 +++++++++++++++++++\n 2 files changed, 63 insertions(+), 4 deletions(-)\n create mode 100644\nlibstdc++-v3/testsuite/std/time/time_zone/numeric_save.cc","diff":"diff --git a/libstdc++-v3/src/c++20/tzdb.cc b/libstdc++-v3/src/c++20/tzdb.cc\nindex b0fbfc46a..1e49bb749 100644\n--- a/libstdc++-v3/src/c++20/tzdb.cc\n+++ b/libstdc++-v3/src/c++20/tzdb.cc\n@@ -478,11 +478,12 @@ namespace std::chrono\n\n ZoneInfo(sys_info&& info)\n : m_buf(std::move(info.abbrev)), m_expanded(true), m_save(info.save),\n- m_offset(info.offset), m_until(info.end)\n+ m_offset(info.offset - seconds(info.save)), m_until(info.end)\n { }\n\n ZoneInfo(const pair& info)\n- : m_expanded(true), m_save(info.first.save),\nm_offset(info.first.offset),\n+ : m_expanded(true), m_save(info.first.save),\n+ m_offset(info.first.offset - seconds(info.first.save)),\n m_until(info.first.end)\n {\n if (info.second.size())\n@@ -494,7 +495,7 @@ namespace std::chrono\n m_buf += info.first.abbrev;\n }\n\n- // STDOFF: Seconds from UTC during standard time.\n+ // STDOFF: Seconds from UTC during standard time (without any save).\n seconds\n offset() const noexcept { return m_offset; }\n\n@@ -539,7 +540,7 @@ namespace std::chrono\n return false;\n\n info.end = until();\n- info.offset = offset();\n+ info.offset = offset() + seconds(m_save);\n info.save = minutes(m_save);\n info.abbrev = format();\n format_abbrev_str(info); // expand %z\ndiff --git a/libstdc++-v3/testsuite/std/time/time_zone/numeric_save.cc\nb/libstdc++-v3/testsuite/std/time/time_zone/numeric_save.cc\nnew file mode 100644\nindex 000000000..1b5b22263\n--- /dev/null\n+++ b/libstdc++-v3/testsuite/std/time/time_zone/numeric_save.cc\n@@ -0,0 +1,58 @@\n+// { dg-do run { target c++20 } }\n+// { dg-require-effective-target tzdb }\n+// { dg-require-effective-target cxx11_abi }\n+// { dg-xfail-run-if \"no weak override on AIX\" { powerpc-ibm-aix* } }\n+\n+// When a Zone line specifies a numeric value as its RULES field, that\n+// value is the constant DST save value for that zone line. Per\n+// [time.zone.info.sys] sys_info::offset is the total UTC offset\n+// (stdoff + save).\n+\n+#include \n+#include \n+#include \n+\n+static bool override_used = false;\n+\n+namespace __gnu_cxx\n+{\n+ const char* zoneinfo_dir_override() {\n+ override_used = true;\n+ return \"./\";\n+ }\n+}\n+\n+int\n+main()\n+{\n+ using namespace std::chrono;\n+\n+ std::ofstream(\"tzdata.zi\") << R\"(# version test_numeric_save\n+Z Test/Gaborone 2 - CAT 1943 Sep 19 2\n+ 2 1 CAST 1944 Mar 19 2\n+ 2 - CAT\n+)\";\n+\n+ const auto& db = reload_tzdb();\n+ VERIFY( override_used );\n+ VERIFY( db.version == \"test_numeric_save\" );\n+\n+ auto* tz = locate_zone(\"Test/Gaborone\");\n+\n+ // Sample well inside the CAST (numeric-save) zone line.\n+ auto info = tz->get_info(sys_days(1943y/December/15));\n+ VERIFY( info.offset == 3h ); // stdoff +2h + save +1h\n+ VERIFY( info.save == 60min );\n+ VERIFY( info.abbrev == \"CAST\" );\n+\n+ // Bordering zone lines should report the standard offset with save 0.\n+ auto before = tz->get_info(sys_days(1943y/September/1));\n+ VERIFY( before.offset == 2h );\n+ VERIFY( before.save == 0min );\n+ VERIFY( before.abbrev == \"CAT\" );\n+\n+ auto after = tz->get_info(sys_days(1944y/April/15));\n+ VERIFY( after.offset == 2h );\n+ VERIFY( after.save == 0min );\n+ VERIFY( after.abbrev == \"CAT\" );\n+}\n","prefixes":["v2","1/5"]}