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// run-pass
// compile-flags: -C debug-assertions
// Check that we do *not* overflow on a number of edge cases.
// (compare with test/run-fail/overflowing-{lsh,rsh}*.rs)
fn main() {
test_left_shift();
test_right_shift();
}
pub static mut HACK: i32 = 0;
// Work around constant-evaluation
// The point of this test is to exercise the code generated for execution at runtime,
// `id` can never be flagged as a const fn by future aggressive analyses...
// due to the modification of the static
#[inline(never)]
fn id<T>(x: T) -> T {
unsafe { HACK += 1; }
x
}
fn test_left_shift() {
// negative rhs can panic, but values in [0,N-1] are okay for iN
macro_rules! tests {
($iN:ty, $uN:ty, $max_rhs:expr, $expect_i:expr, $expect_u:expr) => { {
let x = (1 as $iN) << id(0);
assert_eq!(x, 1);
let x = (1 as $uN) << id(0);
assert_eq!(x, 1);
let x = (1 as $iN) << id($max_rhs);
assert_eq!(x, $expect_i);
let x = (1 as $uN) << id($max_rhs);
assert_eq!(x, $expect_u);
// high-order bits on LHS are silently discarded without panic.
let x = (3 as $iN) << id($max_rhs);
assert_eq!(x, $expect_i);
let x = (3 as $uN) << id($max_rhs);
assert_eq!(x, $expect_u);
} }
}
let x = 1_i8 << id(0);
assert_eq!(x, 1);
let x = 1_u8 << id(0);
assert_eq!(x, 1);
let x = 1_i8 << id(7);
assert_eq!(x, i8::MIN);
let x = 1_u8 << id(7);
assert_eq!(x, 0x80);
// high-order bits on LHS are silently discarded without panic.
let x = 3_i8 << id(7);
assert_eq!(x, i8::MIN);
let x = 3_u8 << id(7);
assert_eq!(x, 0x80);
// above is (approximately) expanded from:
tests!(i8, u8, 7, i8::MIN, 0x80_u8);
tests!(i16, u16, 15, i16::MIN, 0x8000_u16);
tests!(i32, u32, 31, i32::MIN, 0x8000_0000_u32);
tests!(i64, u64, 63, i64::MIN, 0x8000_0000_0000_0000_u64);
}
fn test_right_shift() {
// negative rhs can panic, but values in [0,N-1] are okay for iN
macro_rules! tests {
($iN:ty, $uN:ty, $max_rhs:expr,
$signbit_i:expr, $highbit_i:expr, $highbit_u:expr) =>
{ {
let x = (1 as $iN) >> id(0);
assert_eq!(x, 1);
let x = (1 as $uN) >> id(0);
assert_eq!(x, 1);
let x = ($highbit_i) >> id($max_rhs-1);
assert_eq!(x, 1);
let x = ($highbit_u) >> id($max_rhs);
assert_eq!(x, 1);
// sign-bit is carried by arithmetic right shift
let x = ($signbit_i) >> id($max_rhs);
assert_eq!(x, -1);
// low-order bits on LHS are silently discarded without panic.
let x = ($highbit_i + 1) >> id($max_rhs-1);
assert_eq!(x, 1);
let x = ($highbit_u + 1) >> id($max_rhs);
assert_eq!(x, 1);
let x = ($signbit_i + 1) >> id($max_rhs);
assert_eq!(x, -1);
} }
}
tests!(i8, u8, 7, i8::MIN, 0x40_i8, 0x80_u8);
tests!(i16, u16, 15, i16::MIN, 0x4000_u16, 0x8000_u16);
tests!(i32, u32, 31, i32::MIN, 0x4000_0000_u32, 0x8000_0000_u32);
tests!(i64, u64, 63, i64::MIN,
0x4000_0000_0000_0000_u64, 0x8000_0000_0000_0000_u64);
}
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