84 lines
2.6 KiB
Rust
84 lines
2.6 KiB
Rust
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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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// Regression test for Issue 25199: Check that one cannot hide a
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// destructor's access to borrowed data behind a boxed trait object.
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//
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// Prior to fixing Issue 25199, this example was able to be compiled
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// with rustc, and thus when you ran it, you would see the `Drop` impl
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// for `Test` accessing state that had already been dropping (which is
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// marked explicitly here with checking code within the `Drop` impl
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// for `VecHolder`, but in the general case could just do unsound
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// things like accessing memory that has been freed).
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//
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// Note that I would have liked to encode my go-to example of cyclic
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// structure that accesses its neighbors in drop (and thus is
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// fundamentally unsound) via this trick, but the closest I was able
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// to come was dropck_trait_cycle_checked.rs, which is not quite as
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// "good" as this regression test because the encoding of that example
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// was forced to attach a lifetime to the trait definition itself
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// (`trait Obj<'a>`) while *this* example is solely
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use std::cell::RefCell;
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trait Obj { }
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struct VecHolder {
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v: Vec<(bool, &'static str)>,
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}
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impl Drop for VecHolder {
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fn drop(&mut self) {
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println!("Dropping Vec");
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self.v[30].0 = false;
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self.v[30].1 = "invalid access: VecHolder dropped already";
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}
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}
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struct Container<'a> {
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v: VecHolder,
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d: RefCell<Vec<Box<Obj+'a>>>,
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}
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impl<'a> Container<'a> {
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fn new() -> Container<'a> {
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Container {
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d: RefCell::new(Vec::new()),
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v: VecHolder {
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v: vec![(true, "valid"); 100]
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}
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}
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}
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fn store<T: Obj+'a>(&'a self, val: T) {
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self.d.borrow_mut().push(Box::new(val));
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}
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}
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struct Test<'a> {
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test: &'a Container<'a>,
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}
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impl<'a> Obj for Test<'a> { }
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impl<'a> Drop for Test<'a> {
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fn drop(&mut self) {
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for e in &self.test.v.v {
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assert!(e.0, e.1);
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}
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}
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}
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fn main() {
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let container = Container::new();
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let test = Test{test: &container}; //~ ERROR `container` does not live long enough
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println!("container.v[30]: {:?}", container.v.v[30]);
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container.store(test); //~ ERROR `container` does not live long enough
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}
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