https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92616
Bug ID: 92616
Summary: Inconsistency in time between system_clock::now() and
time(nullptr)
Product: gcc
Version: 8.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: anthony.ajw at gmail dot com
Target Milestone: ---
Created attachment 47321
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=47321&action=edit
system_clock::now vs time(nullptr) inconsistency
I have some code which uses std::this_thread::sleep_until to wait until a
specific time
The target time is set from a time_t value using
std::chrono::system_clock::from_time_t(). Consistently, after waking, the value
returned by time(nullptr) is less than the target time. However, the time
returned by std::chrono::system_clock::now() is greater than the current time.
e.g. the attached code creates the following output:
Now (sc) time is 1574342217233406476 (system clock)
=>1574342217(time_t)
=>13:16:57
Now (time(nullptr)) time is 1574342217(time_t)
=>13:16:57
Now (sc) time is 1574342219000231775 (system clock)
=>1574342219(time_t)
=>13:16:59
Now (time(nullptr)) time is 1574342218(time_t)
=>13:16:58
As you can see, when woken, the time return by time(nullptr) is earlier than
the corresponding time_t conversion from system_clock::now().
FYI, this is compiled using the g++-8.3.0 from the ubuntu 18.04 repos.
g++ --version outputs:
g++ (Ubuntu 8.3.0-6ubuntu1~18.04.1) 8.3.0
