src/test/run-pass/shift-near-oflo.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // compile-flags: -C debug-assertions
  12
  13 // Check that we do *not* overflow on a number of edge cases.
  14 // (compare with test/run-fail/overflowing-{lsh,rsh}*.rs)
  15
  16 fn main() {
  17     test_left_shift();
  18     test_right_shift();
  19 }
  20
  21 fn test_left_shift() {
  22     // negative rhs can panic, but values in [0,N-1] are okay for iN
  23
  24     macro_rules! tests {
  25         ($iN:ty, $uN:ty, $max_rhs:expr, $expect_i:expr, $expect_u:expr) => { {
  26             let x = (1 as $iN) << 0;
  27             assert_eq!(x, 1);
  28             let x = (1 as $uN) << 0;
  29             assert_eq!(x, 1);
  30             let x = (1 as $iN) << $max_rhs;
  31             assert_eq!(x, $expect_i);
  32             let x = (1 as $uN) << $max_rhs;
  33             assert_eq!(x, $expect_u);
  34             // high-order bits on LHS are silently discarded without panic.
  35             let x = (3 as $iN) << $max_rhs;
  36             assert_eq!(x, $expect_i);
  37             let x = (3 as $uN) << $max_rhs;
  38             assert_eq!(x, $expect_u);
  39         } }
  40     }
  41
  42     let x = 1_i8 << 0;
  43     assert_eq!(x, 1);
  44     let x = 1_u8 << 0;
  45     assert_eq!(x, 1);
  46     let x = 1_i8 << 7;
  47     assert_eq!(x, std::i8::MIN);
  48     let x = 1_u8 << 7;
  49     assert_eq!(x, 0x80);
  50     // high-order bits on LHS are silently discarded without panic.
  51     let x = 3_i8 << 7;
  52     assert_eq!(x, std::i8::MIN);
  53     let x = 3_u8 << 7;
  54     assert_eq!(x, 0x80);
  55
  56     // above is (approximately) expanded from:
  57     tests!(i8, u8, 7, std::i8::MIN, 0x80_u8);
  58
  59     tests!(i16, u16, 15, std::i16::MIN, 0x8000_u16);
  60     tests!(i32, u32, 31, std::i32::MIN, 0x8000_0000_u32);
  61     tests!(i64, u64, 63, std::i64::MIN, 0x8000_0000_0000_0000_u64);
  62 }
  63
  64 fn test_right_shift() {
  65     // negative rhs can panic, but values in [0,N-1] are okay for iN
  66
  67     macro_rules! tests {
  68         ($iN:ty, $uN:ty, $max_rhs:expr,
  69          $signbit_i:expr, $highbit_i:expr, $highbit_u:expr) =>
  70         { {
  71             let x = (1 as $iN) >> 0;
  72             assert_eq!(x, 1);
  73             let x = (1 as $uN) >> 0;
  74             assert_eq!(x, 1);
  75             let x = ($highbit_i) >> $max_rhs-1;
  76             assert_eq!(x, 1);
  77             let x = ($highbit_u) >> $max_rhs;
  78             assert_eq!(x, 1);
  79             // sign-bit is carried by arithmetic right shift
  80             let x = ($signbit_i) >> $max_rhs;
  81             assert_eq!(x, -1);
  82             // low-order bits on LHS are silently discarded without panic.
  83             let x = ($highbit_i + 1) >> $max_rhs-1;
  84             assert_eq!(x, 1);
  85             let x = ($highbit_u + 1) >> $max_rhs;
  86             assert_eq!(x, 1);
  87             let x = ($signbit_i + 1) >> $max_rhs;
  88             assert_eq!(x, -1);
  89         } }
  90     }
  91
  92     tests!(i8, u8, 7, std::i8::MIN, 0x40_i8, 0x80_u8);
  93     tests!(i16, u16, 15, std::i16::MIN, 0x4000_u16, 0x8000_u16);
  94     tests!(i32, u32, 31, std::i32::MIN, 0x4000_0000_u32, 0x8000_0000_u32);
  95     tests!(i64, u64, 63, std::i64::MIN,
  96            0x4000_0000_0000_0000_u64, 0x8000_0000_0000_0000_u64);
  97 }