| // 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 'attempted to shift left with overflow' |
| // compile-flags: -C debug-assertions |
| |
| // This function is checking that our automatic truncation does not |
| // sidestep the overflow checking. |
| |
| #![warn(exceeding_bitshifts)] |
| |
| 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); |
| } |
