src/test/ui/numbers-arithmetic/overflowing-rsh-4.rs

   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
   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 }