thread 'main' panicked at 'called time::OffsetDateTime::now_local().unwrap() on an Err value: IndeterminateOffset'

[zhuxiujia]

thread 'main' panicked at 'called Result::unwrap() on an Err value: IndeterminateOffset'

os: MacOS Big Sur

[jhpratt]

The method is fallible for a reason. Don't call .unwrap().

[zhuxiujia]

The method is fallible for a reason. Don't call .unwrap().

But can't get local time on MacOS?

[jhpratt]

With the version published on crates.io, no. It will be supported in the next release, but only when the program does not have multiple threads running. You should explicitly handle the error case in any situation.

[zhuxiujia]

在 crates.io 上发布的版本，没有。它将在下一个版本中支持，但仅限于程序没有运行多个线程时。在任何情况下，您都应该明确处理错误情况。

Ok, now I use the

let mut now = time: : OffsetDateTime: : now_utc ();

let off = UtcOffset::from_whole_seconds(chrono::offset::Local::now().offset().local_minus_utc()).unwrap();

now = now.to_offset(off);

Instead of this.
Perhaps you can refer to chrono's implementation?

[jhpratt]

What chrono does is unsound and can crash your program completely and without warning. It is a security concern. Time does not have this problem. That is why it will be restricted to single-threaded programs in the next release.

[zhuxiujia]

What chrono does is unsound and can crash your program completely and without warning. It is a security concern. Time does not have this problem. That is why it will be restricted to single-threaded programs in the next release.

So I call this method only if I have a mutex, right? To ensure that it cannot be accessed by multiple threads at the same time

[jhpratt]

That is not correct. If you have multiple threads running, the method will fail on MacOS.

[zhuxiujia]

That is not correct. If you have multiple threads running, the method will fail on MacOS.

oh, maybe i should save in to Lazy Global data
for example:

pub const GLOBAL_OFFSET:Lazy<UtcOffset>=Lazy::new(||{
     UtcOffset::from_whole_seconds(chrono::offset::Local::now().offset().local_minus_utc()).unwrap()
});

So time zone data is only fetched once。

thanks

[jhpratt]

If you call chrono::offset::Local::now() with multiple threads running, the result is undefined behavior. Once again, this means your program can crash unexpectedly. Wrapping in Lazy does not change this. There is no way around the multithreaded unsoundness when using the chrono crate. Any manner in which you do so will fail unless you can guarantee that there is only a single thread running — this is what the time crate does.

Chrono is unsound. If you use the time crate, you will not encounter unsoundness. That is a guarantee I provide.

[zhuxiujia]

If you call chrono::offset::Local::now() with multiple threads running, the result is undefined behavior. Once again, this means your program can crash unexpectedly. Wrapping in Lazy does not change this. There is no way around the multithreaded unsoundness when using the chrono crate. Any manner in which you do so will fail unless you can guarantee that there is only a single thread running — this is what the time crate does.

Chrono is unsound. If you use the time crate, you will not encounter unsoundness. That is a guarantee I provide.

Ok, this is a temporary solution, pending a new version of Time。
thanks again.

should be this。 （The test will only initialize once）

pub static  GLOBAL_OFFSET: Lazy<UtcOffset> = Lazy::new(|| {
    println!("init time");
    UtcOffset::from_whole_seconds(chrono::offset::Local::now().offset().local_minus_utc()).unwrap()
});