diff options
Diffstat (limited to 'src/test/ui/span/vec-must-not-hide-type-from-dropck.rs')
-rw-r--r-- | src/test/ui/span/vec-must-not-hide-type-from-dropck.rs | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/src/test/ui/span/vec-must-not-hide-type-from-dropck.rs b/src/test/ui/span/vec-must-not-hide-type-from-dropck.rs new file mode 100644 index 000000000..9bfbfab06 --- /dev/null +++ b/src/test/ui/span/vec-must-not-hide-type-from-dropck.rs @@ -0,0 +1,125 @@ +// Checking that `Vec<T>` cannot hide lifetimes within `T` when `T` +// implements `Drop` and might access methods of values that have +// since been deallocated. +// +// In this case, the values in question hold (non-zero) unique-ids +// that zero themselves out when dropped, and are wrapped in another +// type with a destructor that asserts that the ids it references are +// indeed non-zero (i.e., effectively checking that the id's are not +// dropped while there are still any outstanding references). +// +// However, the values in question are also formed into a +// cyclic-structure, ensuring that there is no way for all of the +// conditions above to be satisfied, meaning that if the dropck is +// sound, it should reject this code. + + + +use std::cell::Cell; +use id::Id; + +mod s { + use std::sync::atomic::{AtomicUsize, Ordering}; + + static S_COUNT: AtomicUsize = AtomicUsize::new(0); + + /// generates globally unique count (global across the current + /// process, that is) + pub fn next_count() -> usize { + S_COUNT.fetch_add(1, Ordering::SeqCst) + 1 + } +} + +mod id { + use s; + + /// Id represents a globally unique identifier (global across the + /// current process, that is). When dropped, it automatically + /// clears its `count` field, but leaves `orig_count` untouched, + /// so that if there are subsequent (erroneous) invocations of its + /// method (which is unsound), we can observe it by seeing that + /// the `count` is 0 while the `orig_count` is non-zero. + #[derive(Debug)] + pub struct Id { + orig_count: usize, + count: usize, + } + + impl Id { + /// Creates an `Id` with a globally unique count. + pub fn new() -> Id { + let c = s::next_count(); + println!("building Id {}", c); + Id { orig_count: c, count: c } + } + /// returns the `count` of self; should be non-zero if + /// everything is working. + pub fn count(&self) -> usize { + println!("Id::count on {} returns {}", self.orig_count, self.count); + self.count + } + } + + impl Drop for Id { + fn drop(&mut self) { + println!("dropping Id {}", self.count); + self.count = 0; + } + } +} + +trait HasId { + fn count(&self) -> usize; +} + +#[derive(Debug)] +struct CheckId<T:HasId> { + v: T +} + +#[allow(non_snake_case)] +fn CheckId<T:HasId>(t: T) -> CheckId<T> { CheckId{ v: t } } + +impl<T:HasId> Drop for CheckId<T> { + fn drop(&mut self) { + assert!(self.v.count() > 0); + } +} + +#[derive(Debug)] +struct C<'a> { + id: Id, + v: Vec<CheckId<Cell<Option<&'a C<'a>>>>>, +} + +impl<'a> HasId for Cell<Option<&'a C<'a>>> { + fn count(&self) -> usize { + match self.get() { + None => 1, + Some(c) => c.id.count(), + } + } +} + +impl<'a> C<'a> { + fn new() -> C<'a> { + C { id: Id::new(), v: Vec::new() } + } +} + +fn f() { + let (mut c1, mut c2); + c1 = C::new(); + c2 = C::new(); + + c1.v.push(CheckId(Cell::new(None))); + c2.v.push(CheckId(Cell::new(None))); + c1.v[0].v.set(Some(&c2)); + //~^ ERROR `c2` does not live long enough + c2.v[0].v.set(Some(&c1)); + //~^ ERROR `c1` does not live long enough +} + +fn main() { + f(); +} |