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Auto merge of #27582 - pnkfelix:disable-nonzeroing-move-hint-by-defau…
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…lt, r=nikomatsakis

Turn nonzeroing move hints back off by default.

Works around bugs injected by PR #26173.

 * (@pnkfelix is unavailable in the short-term (i.e. for the next week) to fix them.)

 * When the bugs are fixed, we will turn nonzeroing move hints back on by default.

Fix #27401
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bors committed Aug 7, 2015
2 parents ab77c1d + 1a68b18 commit 1b5d521
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Showing 3 changed files with 39 additions and 3 deletions.
4 changes: 2 additions & 2 deletions src/librustc/session/config.rs
Original file line number Diff line number Diff line change
Expand Up @@ -596,8 +596,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
"Force drop flag checks on or off"),
trace_macros: bool = (false, parse_bool,
"For every macro invocation, print its name and arguments"),
disable_nonzeroing_move_hints: bool = (false, parse_bool,
"Force nonzeroing move optimization off"),
enable_nonzeroing_move_hints: bool = (false, parse_bool,
"Force nonzeroing move optimization on"),
}

pub fn default_lib_output() -> CrateType {
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2 changes: 1 addition & 1 deletion src/librustc/session/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -273,7 +273,7 @@ impl Session {
self.opts.debugging_opts.print_enum_sizes
}
pub fn nonzeroing_move_hints(&self) -> bool {
!self.opts.debugging_opts.disable_nonzeroing_move_hints
self.opts.debugging_opts.enable_nonzeroing_move_hints
}
pub fn sysroot<'a>(&'a self) -> &'a Path {
match self.opts.maybe_sysroot {
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36 changes: 36 additions & 0 deletions src/test/run-pass/issue-27401-dropflag-reinit.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,36 @@
// Copyright 2015 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.

// ignore-pretty #27582

// Check that when a `let`-binding occurs in a loop, its associated
// drop-flag is reinitialized (to indicate "needs-drop" at the end of
// the owning variable's scope).

struct A<'a>(&'a mut i32);

impl<'a> Drop for A<'a> {
fn drop(&mut self) {
*self.0 += 1;
}
}

fn main() {
let mut cnt = 0;
for i in 0..2 {
let a = A(&mut cnt);
if i == 1 { // Note that
break; // both this break
} // and also
drop(a); // this move of `a`
// are necessary to expose the bug
}
assert_eq!(cnt, 2);
}

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