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* [gcc r13-6396] libstdc++: Make std::chrono::current_zone() default to UTC
@ 2023-03-01 21:26 Jonathan Wakely
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From: Jonathan Wakely @ 2023-03-01 21:26 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:4abd5bc600193e821fbc41995a0b8d9ea42b42c3
commit r13-6396-g4abd5bc600193e821fbc41995a0b8d9ea42b42c3
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Tue Feb 28 21:07:48 2023 +0000
libstdc++: Make std::chrono::current_zone() default to UTC
This is consistent with the behaviour of glibc, which assumes UTC when
/etc/localtime and TZ do not identify a valid time zone. The fallback
tzdb used when no valid tzdata exists always contains the UTC zone, so
this change means we have a valid tzdb and valid current zone even in
the degenerate case.
With this default we no longer need the AIX-specific kluge to try and
identify TZ values specifying a 0-offset zone. We can just use the UTC
default for those, as it has the same effect.
It's still possible for chrono::current_zone() to fail, because the user
could have provided a custom tzdata.zi file which doesn't contain the
UTC time zone, so the "UTC" default would fail to find a valid zone, and
throw an exception. That's just user error, they should not provide bad
data and expect reasonable behaviour.
libstdc++-v3/ChangeLog:
* src/c++20/tzdb.cc (chrono::tzdb::current_zone()) Use "UTC" if
current time zone cannot be determined.
* testsuite/std/time/tzdb/1.cc: Remove conditions based on
HAVE_TZDB macro and test all members unconditionally.
Diff:
---
libstdc++-v3/src/c++20/tzdb.cc | 15 ++++++---------
libstdc++-v3/testsuite/std/time/tzdb/1.cc | 22 +++++++++++-----------
2 files changed, 17 insertions(+), 20 deletions(-)
diff --git a/libstdc++-v3/src/c++20/tzdb.cc b/libstdc++-v3/src/c++20/tzdb.cc
index 2e7e173f0ef..2b68888e3b9 100644
--- a/libstdc++-v3/src/c++20/tzdb.cc
+++ b/libstdc++-v3/src/c++20/tzdb.cc
@@ -1692,19 +1692,16 @@ namespace std::chrono
// https://www.ibm.com/support/pages/managing-time-zone-variable-posix
if (const char* env = std::getenv("TZ"))
{
- string_view s(env);
- if (s == "GMT0")
- s = "Etc/GMT";
- else if (s.size() == 4 && s[3] == '0')
- s = "Etc/UTC";
-
- // This will fail unless TZ contains an IANA time zone name,
- // or one of the special cases above.
- if (auto tz = do_locate_zone(this->zones, this->links, s))
+ // This will fail unless TZ contains an IANA time zone name.
+ if (auto tz = do_locate_zone(this->zones, this->links, env))
return tz;
}
#endif
+ // Default to UTC.
+ if (auto tz = do_locate_zone(this->zones, this->links, "UTC"))
+ return tz;
+
__throw_runtime_error("tzdb: cannot determine current zone");
}
diff --git a/libstdc++-v3/testsuite/std/time/tzdb/1.cc b/libstdc++-v3/testsuite/std/time/tzdb/1.cc
index 64e42701d3b..877a55b8d31 100644
--- a/libstdc++-v3/testsuite/std/time/tzdb/1.cc
+++ b/libstdc++-v3/testsuite/std/time/tzdb/1.cc
@@ -1,7 +1,6 @@
// { dg-options "-std=gnu++20" }
// { dg-do run { target c++20 } }
// { dg-require-effective-target cxx11_abi }
-// { dg-additional-options "-DHAVE_TZDB" { target tzdb } }
#include <chrono>
#include <testsuite_hooks.h>
@@ -14,22 +13,25 @@ test_version()
const tzdb& db = get_tzdb();
VERIFY( &db == &get_tzdb_list().front() );
-#ifdef HAVE_TZDB
- VERIFY( db.version == remote_version() );
- const tzdb& reloaded = reload_tzdb();
- if (reloaded.version == db.version)
- VERIFY( &reloaded == &db );
-#endif
+ const char* func;
+ try {
+ func = "remote_version";
+ VERIFY( db.version == remote_version() );
+ func = "reload_tzdb";
+ const tzdb& reloaded = reload_tzdb();
+ if (reloaded.version == db.version)
+ VERIFY( &reloaded == &db );
+ } catch (const std::exception&) {
+ std::printf("std::chrono::%s() failed\n", func);
+ }
}
void
test_current()
{
-#ifdef HAVE_TZDB
const tzdb& db = get_tzdb();
const time_zone* tz = db.current_zone();
VERIFY( tz == std::chrono::current_zone() );
-#endif
}
void
@@ -43,9 +45,7 @@ test_locate()
VERIFY( tz == db.locate_zone("Etc/GMT") );
VERIFY( tz == db.locate_zone("Etc/GMT+0") );
-#ifdef HAVE_TZDB
VERIFY( db.locate_zone(db.current_zone()->name()) == db.current_zone() );
-#endif
}
int main()
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