mirror of
https://github.com/rust-lang/rust.git
synced 2024-11-01 15:01:51 +00:00
25 lines
902 B
Rust
25 lines
902 B
Rust
// build-fail
|
|
// compile-flags: -C debug-assertions
|
|
|
|
// This function is checking that our automatic truncation does not
|
|
// sidestep the overflow checking.
|
|
|
|
#![deny(arithmetic_overflow)]
|
|
|
|
fn main() {
|
|
// this signals overflow when checking is on
|
|
let x = 1_i8 << 17;
|
|
//~^ ERROR: this arithmetic operation will overflow
|
|
|
|
// ... 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);
|
|
}
|