All access to a static is safe, but there are a number of restrictions on statics:
The type must have the Sync trait bound to allow thread-safe access.
Constants cannot refer to statics.It can be confusing whether or not you should use a constant item or a static item. Constants should, in general, be preferred over statics unless one of the following are true:
Large amounts of data are being stored
The single-address property of statics is required.
Interior mutability is required.
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Another difference between constants and static variables is that static variables can be mutable.
Accessing and modifying mutable static variables is unsafe
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