mirror of https://github.com/rust-lang/rust
25 lines
904 B
Rust
25 lines
904 B
Rust
//@ build-fail
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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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#![deny(arithmetic_overflow)]
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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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//~^ ERROR: this arithmetic operation will overflow
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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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