Fix compile-time integer overflow when using ! on unsigned values
Since the values are stored in a u64 internally, we need to be mask away the high bits after applying the ! operator. Otherwise, these bits will be set to one, causing overflow.
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@ -1,4 +1,4 @@
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// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
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// Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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@ -34,7 +34,7 @@ use std::borrow::{Cow, IntoCow};
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use std::num::wrapping::OverflowingOps;
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use std::cmp::Ordering;
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use std::collections::hash_map::Entry::Vacant;
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use std::{i8, i16, i32, i64};
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use std::{i8, i16, i32, i64, u8, u16, u32, u64};
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use std::rc::Rc;
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fn lookup_const<'a>(tcx: &'a ty::ctxt, e: &Expr) -> Option<&'a Expr> {
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@ -461,6 +461,16 @@ pub fn const_uint_checked_neg<'a>(
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Ok(const_uint((!a).wrapping_add(1)))
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}
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fn const_uint_not(a: u64, opt_ety: Option<UintTy>) -> const_val {
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let mask = match opt_ety {
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Some(UintTy::U8) => u8::MAX as u64,
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Some(UintTy::U16) => u16::MAX as u64,
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Some(UintTy::U32) => u32::MAX as u64,
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None | Some(UintTy::U64) => u64::MAX,
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};
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const_uint(!a & mask)
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}
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macro_rules! overflow_checking_body {
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($a:ident, $b:ident, $ety:ident, $overflowing_op:ident,
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lhs: $to_8_lhs:ident $to_16_lhs:ident $to_32_lhs:ident,
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@ -677,7 +687,7 @@ pub fn eval_const_expr_partial<'tcx>(tcx: &ty::ctxt<'tcx>,
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ast::ExprUnary(ast::UnNot, ref inner) => {
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match try!(eval_const_expr_partial(tcx, &**inner, ety)) {
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const_int(i) => const_int(!i),
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const_uint(i) => const_uint(!i),
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const_uint(i) => const_uint_not(i, expr_uint_type),
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const_bool(b) => const_bool(!b),
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const_str(_) => signal!(e, NotOnString),
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const_float(_) => signal!(e, NotOnFloat),
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21
src/test/run-pass/issue-23968-const-not-overflow.rs
Normal file
21
src/test/run-pass/issue-23968-const-not-overflow.rs
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@ -0,0 +1,21 @@
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// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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const U8_MAX_HALF: u8 = !0u8 / 2;
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const U16_MAX_HALF: u16 = !0u16 / 2;
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const U32_MAX_HALF: u32 = !0u32 / 2;
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const U64_MAX_HALF: u64 = !0u64 / 2;
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fn main() {
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assert_eq!(U8_MAX_HALF, 0x7f);
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assert_eq!(U16_MAX_HALF, 0x7fff);
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assert_eq!(U32_MAX_HALF, 0x7fff_ffff);
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assert_eq!(U64_MAX_HALF, 0x7fff_ffff_ffff_ffff);
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}
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