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// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// ignore-pretty : (#23623) problems when ending with // comments
// error-pattern:thread '<main>' panicked at 'shift operation overflowed'
// compile-flags: -C debug-assertions
// This function is checking that our automatic truncation does not
// sidestep the overflow checking.
#![warn(exceeding_bitshifts)]
#![feature(rustc_attrs)]
#[rustc_no_mir] // FIXME #29769 MIR overflow checking is TBD.
fn main() {
// this signals overflow when checking is on
let x = 1_i8 << 17;
// ... but when checking is off, the fallback will truncate the
// input to its lower three bits (= 1). Note that this is *not*
// the behavior of the x86 processor for 8- and 16-bit types,
// but it is necessary to avoid undefined behavior from LLVM.
//
// We check that here, by ensuring the result has only been
// shifted by one place; if overflow checking is turned off, then
// this assertion will pass (and the compiletest driver will
// report that the test did not produce the error expected above).
assert_eq!(x, 2_i8);
}
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