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