[英]msvc std::chrono::time_zone::get_info throws an exception saying: The operation completed successfully
在使用std::format
显示它之前,我试图将从std::chrono::system_clock
返回的 utc 时间转换为本地时间,但是我从std::chrono::time_zone::to_local
得到了一个令人惊讶的异常,它的消息是这样的: The operation completed successfully.
真是惊喜! 我研究了这个方法,它在传递的时间参数上调用了std::chrono::time_zone::get_info
并做了一个简单的转换,所以我分别测试了std::chrono::time_zone::get_info
,它是这个异常的来源. 我不知道这是实现中的错误还是我的代码有错误?
这是抛出此错误的简单代码:
try
{
const std::chrono::time_zone* current_z = std::chrono::current_zone();
std::cout << "current timezone name: " << current_z->name() << "\n";
auto sys_time = std::chrono::system_clock::now();
std::cout << "current system time: " << sys_time << "\n";
auto sys_info = current_z->get_info(sys_time); // throws exception what(): The operation completed successfully.
std::cout << "sys_info: offset: " << sys_info.offset << ", abbrev" << sys_info.abbrev << "\n";
//auto local_time = current_z->to_local(sys_time); // throws exception since it calls get_info
//std::cout << "current local time: " << local_time << "\n";
}
catch (const std::exception& ex)
{
std::cout << "caught exception: " << ex.what();
}
编辑:查看std::chrono::time_zone::get_info
源代码后,它将调用此方法: std::chrono::time_zone::_Get_info
及其来源
template <class _Duration>
_NODISCARD sys_info _Get_info(const _Duration& _Dur) const {
using _Internal_duration = duration<__std_tzdb_epoch_milli, milli>;
const auto _Internal_dur = _CHRONO duration_cast<_Internal_duration>(_Dur);
const unique_ptr<__std_tzdb_sys_info, _Tzdb_deleter<__std_tzdb_sys_info>> _Info{
__std_tzdb_get_sys_info(_Name.c_str(), _Name.length(), _Internal_dur.count())};
if (_Info == nullptr) {
_Xbad_alloc();
} else if (_Info->_Err == __std_tzdb_error::_Win_error) {
_XGetLastError();
} else if (_Info->_Err == __std_tzdb_error::_Icu_error) {
_Xruntime_error("Internal error loading IANA database information");
}
constexpr auto _Min_internal =
_CHRONO duration_cast<_Internal_duration>(_Min_seconds.time_since_epoch()).count();
constexpr auto _Max_internal =
_CHRONO duration_cast<_Internal_duration>(_Max_seconds.time_since_epoch()).count();
const auto _Begin =
_Info->_Begin <= _Min_internal
? _Min_seconds
: sys_seconds{_CHRONO duration_cast<sys_seconds::duration>(_Internal_duration{_Info->_Begin})};
const auto _End =
_Info->_End >= _Max_internal
? _Max_seconds
: sys_seconds{_CHRONO duration_cast<sys_seconds::duration>(_Internal_duration{_Info->_End})};
return {.begin = _Begin,
.end = _End,
.offset = _CHRONO duration_cast<seconds>(_Internal_duration{_Info->_Offset}),
.save = _CHRONO duration_cast<minutes>(_Internal_duration{_Info->_Save}),
.abbrev = _Info->_Abbrev};
}
__std_tzdb_get_sys_info
返回的_Info
指针不是nullptr
,但其_Err
设置为 1,等于__std_tzdb_error::_Win_error
因此调用_XGetLastError
以抛出异常,错误代码来自GetLastError
并且它将返回 0 表示没有错误代码,因此抛出异常表明没有错误发生! 似乎是微软 stl 代码中的错误
每https://learn.microsoft.com/en-us/cpp/standard-library/time-zone-class?view=msvc-170
看起来你应该首先使用 get_tzdb() 作为
const auto& timeZoneDatabase = get_tzdb(); // initialize the time zone database
const auto& currentZone = timeZoneDatabase.current_zone();
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.