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1 | // Copyright 2015 The Rust Project Developers. See the COPYRIGHT |
2 | // file at the top-level directory of this distribution and at | |
3 | // http://rust-lang.org/COPYRIGHT. | |
4 | // | |
5 | // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | |
6 | // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | |
7 | // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | |
8 | // option. This file may not be copied, modified, or distributed | |
9 | // except according to those terms. | |
10 | ||
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11 | // ignore-pretty : (#23623) problems when ending with // comments |
12 | ||
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13 | // error-pattern:thread '<main>' panicked at 'shift operation overflowed' |
14 | // compile-flags: -C debug-assertions | |
15 | ||
16 | // This function is checking that our automatic truncation does not | |
17 | // sidestep the overflow checking. | |
18 | ||
b039eaaf | 19 | #![warn(exceeding_bitshifts)] |
c34b1796 | 20 | |
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21 | #![feature(rustc_attrs)] |
22 | #[rustc_no_mir] // FIXME #29769 MIR overflow checking is TBD. | |
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23 | fn main() { |
24 | // this signals overflow when checking is on | |
b039eaaf | 25 | let x = 1_i8 << 17; |
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26 | |
27 | // ... but when checking is off, the fallback will truncate the | |
28 | // input to its lower three bits (= 1). Note that this is *not* | |
29 | // the behavior of the x86 processor for 8- and 16-bit types, | |
30 | // but it is necessary to avoid undefined behavior from LLVM. | |
31 | // | |
32 | // We check that here, by ensuring the result has only been | |
33 | // shifted by one place; if overflow checking is turned off, then | |
34 | // this assertion will pass (and the compiletest driver will | |
35 | // report that the test did not produce the error expected above). | |
36 | assert_eq!(x, 2_i8); | |
37 | } |