1 // build-fail
2 // compile-flags: -C debug-assertions
3
4 // This function is checking that our (type-based) automatic
5 // truncation does not sidestep the overflow checking.
6
7 #![deny(arithmetic_overflow, const_err)]
8
main()9 fn main() {
10 // this signals overflow when checking is on
11 let x = 2_i8 >> 17;
12 //~^ ERROR: this arithmetic operation will overflow
13
14 // ... but when checking is off, the fallback will truncate the
15 // input to its lower three bits (= 1). Note that this is *not*
16 // the behavior of the x86 processor for 8- and 16-bit types,
17 // but it is necessary to avoid undefined behavior from LLVM.
18 //
19 // We check that here, by ensuring the result is not zero; if
20 // overflow checking is turned off, then this assertion will pass
21 // (and the compiletest driver will report that the test did not
22 // produce the error expected above).
23 assert_eq!(x, 1_i8);
24 }
25