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Unit test for proper EndRegion emission on a cyclic reference.

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This commit is contained in:
Felix S. Klock II 2017-08-28 13:39:06 +02:00
parent ab46142bd9
commit 88080bd56a
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src/test/mir-opt/end_region_cyclic.rs Normal file
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// Copyright 2017 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.
// compile-flags: -Z identify_regions -Z span_free_formats -Z emit-end-regions
// ignore-tidy-linelength
// This test models a scenario with a cyclic reference. Rust obviously
// needs to handle such cases.
//
// The interesting part about this test is that such case shows that
// one cannot generally force all references to be dead before you hit
// their EndRegion; at least, not without breaking the more important
// property that all borrowed storage locations have their regions
// ended strictly before their StorageDeads. (This test was inspired
// by discussion on Issue #43481.)
use std::cell::Cell;
struct S<'a> {
r: Cell<Option<&'a S<'a>>>,
}
fn main() {
loop {
let x = S { r: Cell::new(None) };
x.r.set(Some(&x));
if query() { break; }
x.r.set(Some(&x));
}
}
fn query() -> bool { true }
// END RUST SOURCE
// START rustc.node16.SimplifyCfg-qualify-consts.after.mir
// fn main() -> () {
// let mut _0: ();
// scope 1 {
// let _2: S<'35_0rs>;
// }
// let mut _1: ();
// let mut _3: std::cell::Cell<std::option::Option<&'35_0rs S<'35_0rs>>>;
// let mut _4: std::option::Option<&'35_0rs S<'35_0rs>>;
// let mut _5: ();
// let mut _6: &'16s std::cell::Cell<std::option::Option<&'35_0rs S<'35_0rs>>>;
// let mut _7: std::option::Option<&'35_0rs S<'35_0rs>>;
// let mut _8: &'35_0rs S<'35_0rs>;
// let mut _9: &'35_0rs S<'35_0rs>;
// let mut _10: ();
// let mut _11: bool;
// let mut _12: !;
// let mut _13: ();
// let mut _14: &'33s std::cell::Cell<std::option::Option<&'35_0rs S<'35_0rs>>>;
// let mut _15: std::option::Option<&'35_0rs S<'35_0rs>>;
// let mut _16: &'35_0rs S<'35_0rs>;
// let mut _17: &'35_0rs S<'35_0rs>;
// bb0: {
// goto -> bb1;
// }
// bb1: {
// StorageLive(_2);
// StorageLive(_3);
// StorageLive(_4);
// _4 = std::option::Option<&'35_0rs S<'35_0rs>>::None;
// _3 = const <std::cell::Cell<T>>::new(_4) -> bb2;
// }
// bb2: {
// StorageDead(_4);
// _2 = S<'35_0rs> { r: _3 };
// StorageDead(_3);
// StorageLive(_6);
// _6 = &'16s (_2.0: std::cell::Cell<std::option::Option<&'35_0rs S<'35_0rs>>>);
// StorageLive(_7);
// StorageLive(_8);
// StorageLive(_9);
// _9 = &'35_0rs _2;
// _8 = &'35_0rs (*_9);
// _7 = std::option::Option<&'35_0rs S<'35_0rs>>::Some(_8,);
// StorageDead(_8);
// _5 = const <std::cell::Cell<T>>::set(_6, _7) -> bb3;
// }
// bb3: {
// EndRegion('16s);
// StorageDead(_7);
// StorageDead(_6);
// StorageDead(_9);
// StorageLive(_11);
// _11 = const query() -> bb4;
// }
// bb4: {
// switchInt(_11) -> [0u8: bb6, otherwise: bb5];
// }
// bb5: {
// _0 = ();
// StorageDead(_11);
// EndRegion('35_0rs);
// StorageDead(_2);
// return;
// }
// bb6: {
// _10 = ();
// StorageDead(_11);
// StorageLive(_14);
// _14 = &'33s (_2.0: std::cell::Cell<std::option::Option<&'35_0rs S<'35_0rs>>>);
// StorageLive(_15);
// StorageLive(_16);
// StorageLive(_17);
// _17 = &'35_0rs _2;
// _16 = &'35_0rs (*_17);
// _15 = std::option::Option<&'35_0rs S<'35_0rs>>::Some(_16,);
// StorageDead(_16);
// _13 = const <std::cell::Cell<T>>::set(_14, _15) -> bb7;
// }
// bb7: {
// EndRegion('33s);
// StorageDead(_15);
// StorageDead(_14);
// StorageDead(_17);
// _1 = ();
// EndRegion('35_0rs);
// StorageDead(_2);
// goto -> bb1;
// }
// }
// END rustc.node16.SimplifyCfg-qualify-consts.after.mir