Function time::util::local_offset::set_soundness

pub unsafe fn set_soundness(soundness: Soundness)

Set whether obtaining the local UTC offset is allowed to invoke undefined behavior. Use of this function is heavily discouraged.

Safety

If this method is called with Soundness::Sound, the call is always sound. If this method is called with Soundness::Unsound, the following conditions apply.

• If the operating system provides a thread-safe environment, the call is sound.
• If the process is single-threaded, the call is sound.
• If the process is multi-threaded, no other thread may mutate the environment in any way at the same time a call to a method that obtains the local UTC offset. This includes adding, removing, or modifying an environment variable.

The first two conditions are automatically checked by time, such that you do not need to declare your code unsound. Currently, the only known operating systems that does not provide a thread-safe environment are some Unix-like OS’s. All other operating systems should succeed when attempting to obtain the local UTC offset.

Note that you must not only verify this safety condition for your code, but for all code that will be included in the final binary. Notably, it applies to both direct and transitive dependencies and to both Rust and non-Rust code. For this reason it is not possible to soundly pass Soundness::Unsound to this method if you are writing a library that may used by others.

If using this method is absolutely necessary, it is recommended to keep the time between setting the soundness to Soundness::Unsound and setting it back to Soundness::Sound as short as possible.

The following methods currently obtain the local UTC offset:

• OffsetDateTime::now_local
• UtcOffset::local_offset_at
• UtcOffset::current_local_offset