Syntax
- const IDENTIFIER: type = constexpr;
- static [mut] IDENTIFIER: type = expr;
- lazy_static! { static ref IDENTIFIER: type = expr; }
const values are always inlined and have no address in memory.static values are never inlined and have one instance with a fixed address.static mut values are not memory safe and thus can only be accessed in an unsafe block.- Sometimes using global static mutable variables in multi-threaded code can be dangerous, so consider using std::sync::Mutex or other alternatives
lazy_static objects are immutable, are initialized only once, are shared among all threads, and can be directly accessed (there are no wrapper types involved). In contrast, thread_local objects are meant to be mutable, are initialized once for each thread, and accesses are indirect (involving the wrapper type LocalKey<T>)
