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Date overflow with std::chrono::time_point #3725
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I think the issue is here: Lines 2097 to 2103 in dd6f657
and here: Lines 526 to 529 in dd6f657
Hence, simply using this alternative template<typename Duration>
inline std::tm gmtime(
std::chrono::time_point<std::chrono::system_clock, Duration> time_point) {
using large_seconds = std::chrono::duration<std::int64_t>;
return gmtime(std::chrono::time_point_cast<large_seconds>(time_point).time_since_epoch().count());
} (and we can remove the NB: this is assuming that |
I opened a PR with a suggested fix #3727. |
cschreib
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Nov 25, 2023
The function is now more generic and will handle all casts. It also takes care of toggling safe vs unsafe casts using FMT_SAFE_DURATION_CAST.
vitaut
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Nov 25, 2023
* Fix #3725 and rename fmt_safe_duration_cast to fmt_duration_cast The function is now more generic and will handle all casts. It also takes care of toggling safe vs unsafe casts using FMT_SAFE_DURATION_CAST. * Refactor fmt_duration_cast to put #ifdef inside the function * Fix compilation error with FMT_USE_LOCAL_TIME
happymonkey1
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Apr 7, 2024
* Fix fmtlib#3725 and rename fmt_safe_duration_cast to fmt_duration_cast The function is now more generic and will handle all casts. It also takes care of toggling safe vs unsafe casts using FMT_SAFE_DURATION_CAST. * Refactor fmt_duration_cast to put #ifdef inside the function * Fix compilation error with FMT_USE_LOCAL_TIME
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std::chrono::system_clock::time_point
on linux platforms uses nanosecond resolution and a 64 bit signed counter, hence is unable to represent dates beyond year 2262. This can be circumvented by using a customtime_point
with a lower time resolution when doing time calculations, such asusing my_time_point = std::chrono::time_point<std::chrono::system_clock, std::chrono::milliseconds>;
Unfortunately, it seems that fmtlib is unable to correctly format such time points despite the lower time resolution. Here is an example that reproduces the problem:
Output from latest master commit on my system (Ubuntu GCC 11.4; doesn't have
<format>
):Output lines 2 and 3 show the problem of the standard
std::chrono::system_clock::time_point
; this is the output I expect.Output line 5 shows that, using
TimePointGood
with millisecond resolution, the time point itself is able to represent dates far in the future.Output line 6 shows that fmtlib still overflows.
Godbolt link; this is running an older version of fmtlib but it also affected. Using gcc trunk with
std::format
shows that the standardformat
doesn't have the issue and outputs what one would expect:The text was updated successfully, but these errors were encountered: