diff options
Diffstat (limited to 'tests/ui/numbers-arithmetic/shift-near-oflo.rs')
-rw-r--r-- | tests/ui/numbers-arithmetic/shift-near-oflo.rs | 100 |
1 files changed, 100 insertions, 0 deletions
diff --git a/tests/ui/numbers-arithmetic/shift-near-oflo.rs b/tests/ui/numbers-arithmetic/shift-near-oflo.rs new file mode 100644 index 000000000..55006a113 --- /dev/null +++ b/tests/ui/numbers-arithmetic/shift-near-oflo.rs @@ -0,0 +1,100 @@ +// 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); +} |