While bound to true, compilations of +, -, *, inc, dec and the coercions will be done without overflow checks. While bound to :warn-on-boxed, same behavior as true, and a warning is emitted when compilation uses boxed math. Default: false.
user=> (unchecked-add Long/MAX_VALUE 1)
-9223372036854775808
user=> (+ Long/MAX_VALUE 1)
ArithmeticException integer overflow clojure.lang.Numbers.throwIntOverflow
user=> (set! *unchecked-math* true)
true
user=> (+ Long/MAX_VALUE 1)
-9223372036854775808