diff options
| -rw-r--r-- | src/libcore/num/mod.rs | 26 | ||||
| -rw-r--r-- | src/test/run-fail/overflowing-pow-signed.rs (renamed from src/test/run-fail/overflowing-pow.rs) | 0 | ||||
| -rw-r--r-- | src/test/run-fail/overflowing-pow-unsigned.rs | 16 |
3 files changed, 27 insertions, 15 deletions
diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs index 29ee29eb3eb..5c2cc671969 100644 --- a/src/libcore/num/mod.rs +++ b/src/libcore/num/mod.rs @@ -2211,25 +2211,21 @@ macro_rules! uint_impl { let mut base = self; let mut acc = 1; - let mut prev_base = self; - let mut base_oflo = false; - while exp > 0 { + while exp > 1 { if (exp & 1) == 1 { - if base_oflo { - // ensure overflow occurs in the same manner it - // would have otherwise (i.e. signal any exception - // it would have otherwise). - acc = acc * (prev_base * prev_base); - } else { - acc = acc * base; - } + acc = acc * base; } - prev_base = base; - let (new_base, new_base_oflo) = base.overflowing_mul(base); - base = new_base; - base_oflo = new_base_oflo; exp /= 2; + base = base * base; } + + // Deal with the final bit of the exponent separately, since + // squaring the base afterwards is not necessary and may cause a + // needless overflow. + if exp == 1 { + acc = acc * base; + } + acc } diff --git a/src/test/run-fail/overflowing-pow.rs b/src/test/run-fail/overflowing-pow-signed.rs index b0ff0df5577..b0ff0df5577 100644 --- a/src/test/run-fail/overflowing-pow.rs +++ b/src/test/run-fail/overflowing-pow-signed.rs diff --git a/src/test/run-fail/overflowing-pow-unsigned.rs b/src/test/run-fail/overflowing-pow-unsigned.rs new file mode 100644 index 00000000000..d3e7035279f --- /dev/null +++ b/src/test/run-fail/overflowing-pow-unsigned.rs @@ -0,0 +1,16 @@ +// Copyright 2016 The Rust Project Developers. See the COPYRIGHT +// file at the top-level directory of this distribution and at +// http://rust-lang.org/COPYRIGHT. +// +// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or +// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license +// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +// error-pattern:thread 'main' panicked at 'attempt to multiply with overflow' +// compile-flags: -C debug-assertions + +fn main() { + let _x = 2u32.pow(1024); +} |