Replace zeroing-on-drop with filling-on-drop.
This is meant to set the stage for removing *all* zeroing and filling (on drop) in the future.
Note that the code is meant to be entirely abstract with respect to the particular values used for the drop flags: the final commit demonstrates how to go from zeroing-on-drop to filling-on-drop by changing the value of three constants (in two files).
See further discussion on the internals thread:
http://internals.rust-lang.org/t/attention-hackers-filling-drop/1715/11
[breaking-change] especially for structs / enums using `#[unsafe_no_drop_flag]`.
Refactored code so that the drop-flag values for initialized
(`DTOR_NEEDED`) versus dropped (`DTOR_DONE`) are given explicit names.
Add `mem::dropped()` (which with `DTOR_DONE == 0` is semantically the
same as `mem::zeroed`, but the point is that it abstracts away from
the particular choice of value for `DTOR_DONE`).
Filling-drop needs to use something other than `ptr::read_and_zero`,
so I added such a function: `ptr::read_and_drop`. But, libraries
should not use it if they can otherwise avoid it.
Fixes to tests to accommodate filling-drop.
This commit marks as `#[stable]` the `Entry` types for the maps provided
by `std`. The main reason these had been left unstable previously was
uncertainty about an eventual trait design, but several plausible
designs have been proposed that all work fine with the current type definitions.
r? @Gankro
This commit removes the `IndexMut` impls on `HashMap` and `BTreeMap`, in
order to future-proof the API against the eventual inclusion of an
`IndexSet` trait.
Ideally, we would eventually be able to support:
```rust
map[owned_key] = val;
map[borrowed_key].mutating_method(arguments);
&mut map[borrowed_key];
```
but to keep the design space as unconstrained as possible, we do not
currently want to support `IndexMut`, in case some other strategy will
eventually be needed.
Code currently using mutating index notation can use `get_mut` instead.
[breaking-change]
Closes#23448
This commit marks as `#[stable]` the `Entry` types for the maps provided
by `std`. The main reason these had been left unstable previously was
uncertainty about an eventual trait design, but several plausible
designs have been proposed that all work fine with the current type definitions.
* `collections::btree::node`: accommodate (transient) underflow.
* `collections::btree::map`: avoid underflow during `fn next`
for `BTreeMap::range` methods.
* `collections::slice`: note that pnkfelix deliberately used
`new_pos_wrapping` only once; the other cases of arithmetic do not
over- nor underflow, which is a useful property to leave implicitly
checked/documented via the remaining calls to `fn new_pos(..)`.
* `collections::vec_deque` applied wrapping ops (somewhat blindly)
to two implementation methods, and many tests.
* `std::collections:#️⃣:table` : Use `OverflowingOps` trait to
track overflow during `calculate_offsets` and `calculate_allocation`
functions.
Many of the core rust libraries have places that rely on integer
wrapping behaviour. These places have been altered to use the wrapping_*
methods:
* core:#️⃣:sip - A number of macros
* core::str - The `maximal_suffix` method in `TwoWaySearcher`
* rustc::util::nodemap - Implementation of FnvHash
* rustc_back::sha2 - A number of macros and other places
* rand::isaac - Isaac64Rng, changed to use the Wrapping helper type
Some places had "benign" underflow. This is when underflow or overflow
occurs, but the unspecified value is not used due to other conditions.
* collections::bit::Bitv - underflow when `self.nbits` is zero.
* collections:#️⃣:{map,table} - Underflow when searching an empty
table. Did cause undefined behaviour in this case due to an
out-of-bounds ptr::offset based on the underflowed index. However the
resulting pointers would never be read from.
* syntax::ext::deriving::encodable - Underflow when calculating the
index of the last field in a variant with no fields.
These cases were altered to avoid the underflow, often by moving the
underflowing operation to a place where underflow could not happen.
There was one case that relied on the fact that unsigned arithmetic and
two's complement arithmetic are identical with wrapping semantics. This
was changed to use the wrapping_* methods.
Finally, the calculation of variant discriminants could overflow if the
preceeding discriminant was `U64_MAX`. The logic in `rustc::middle::ty`
for this was altered to avoid the overflow completely, while the
remaining places were changed to use wrapping methods. This is because
`rustc::middle::ty::enum_variants` now throws an error when the
calculated discriminant value overflows a `u64`.
This behaviour can be triggered by the following code:
```
enum Foo {
A = U64_MAX,
B
}
```
This commit also implements the remaining integer operators for
Wrapped<T>.
Specifically, the following actions were takend:
* The `copy_memory` and `copy_nonoverlapping_memory` functions
to drop the `_memory` suffix (as it's implied by the functionality). Both
functions are now marked as `#[stable]`.
* The `set_memory` function was renamed to `write_bytes` and is now stable.
* The `zero_memory` function is now deprecated in favor of `write_bytes`
directly.
* The `Unique` pointer type is now behind its own feature gate called `unique`
to facilitate future stabilization.
[breaking-change]
Specifically, the following actions were taken:
* The `copy_memory` and `copy_nonoverlapping_memory` functions
to drop the `_memory` suffix (as it's implied by the functionality). Both
functions are now marked as `#[stable]`.
* The `set_memory` function was renamed to `write_bytes` and is now stable.
* The `zero_memory` function is now deprecated in favor of `write_bytes`
directly.
* The `Unique` pointer type is now behind its own feature gate called `unique`
to facilitate future stabilization.
* All type parameters now are `T: ?Sized` wherever possible and new clauses were
added to the `offset` functions to require that the type is sized.
[breaking-change]
This is a breaking change if missing docs are forbidden in any module or crate.
I had to add documentation to undocumented associated types in libstd and libcore, please let me know if the documentation is inadequate anywhere!
Fixes#20648
This commit stabilizes `std::borrow`, making the following modifications
to catch up the API with language changes:
* It renames `BorrowFrom` to `Borrow`, as was originally intended (but
blocked for technical reasons), and reorders the parameters
accordingly.
* It moves the type parameter of `ToOwned` to an associated type. This
is somewhat less flexible, in that each borrowed type must have a
unique owned type, but leads to a significant simplification for
`Cow`. Flexibility can be regained by using newtyped slices, which is
advisable for other reasons anyway.
* It removes the owned type parameter from `Cow`, making the type much
less verbose.
* Deprecates the `is_owned` and `is_borrowed` predicates in favor of
direct matching.
The above API changes are relatively minor; the basic functionality
remains the same, and essentially the whole module is now marked
`#[stable]`.
[breaking-change]
This breaks all implementors of FromIterator, as they must now accept IntoIterator instead of Iterator. The fix for this is generally trivial (change the bound, and maybe call into_iter() on the argument to get the old argument).
Users of FromIterator should be unaffected because Iterators are IntoIterator.
[breaking-change]
This breaks all implementors of Extend, as they must now accept IntoIterator instead of Iterator. The fix for this is generally trivial (change the bound, and maybe call into_iter() on the argument to get the old argument).
Users of Extend should be unaffected because Iterators are IntoIterator.
[breaking-change]
This commit is an implementation of [RFC 823][rfc] which is another pass over
the `std::hash` module for stabilization. The contents of the module were not
entirely marked stable, but some portions which remained quite similar to the
previous incarnation are now marked `#[stable]`. Specifically:
[rfc]: https://github.com/rust-lang/rfcs/blob/master/text/0823-hash-simplification.md
* `std::hash` is now stable (the name)
* `Hash` is now stable
* `Hash::hash` is now stable
* `Hasher` is now stable
* `SipHasher` is now stable
* `SipHasher::new` and `new_with_keys` are now stable
* `Hasher for SipHasher` is now stable
* Many `Hash` implementations are now stable
All other portions of the `hash` module remain `#[unstable]` as they are less
commonly used and were recently redesigned.
This commit is a breaking change due to the modifications to the `std::hash` API
and more details can be found on the [RFC][rfc].
Closes#22467
[breaking-change]
Now that the necessary associated types exist for the `IntoIterator` trait this
commit stabilizes the trait as-is as well as all existing implementations.
`IntoIterator` now has an extra associated item:
``` rust
trait IntoIterator {
type Item;
type IntoIter: Iterator<Self=Self::Item>;
}
```
This lets you bind the iterator \"`Item`\" directly when writing generic functions:
``` rust
// hypothetical change, not included in this PR
impl Extend<T> for Vec<T> {
// you can now write
fn extend<I>(&mut self, it: I) where I: IntoIterator<Item=T> { .. }
// instead of
fn extend<I: IntoIterator>(&mut self, it: I) where I::IntoIter: Iterator<Item=T> { .. }
}
```
The downside is that now you have to write an extra associated type in your `IntoIterator` implementations:
``` diff
impl<T> IntoIterator for Vec<T> {
+ type Item = T;
type IntoIter = IntoIter<T>;
fn into_iter(self) -> IntoIter<T> { .. }
}
```
Because this breaks all downstream implementations of `IntoIterator`, this is a [breaking-change]
---
r? @aturon
This is in preparation for stabilization of the `IntoIterator` trait. All
implementations and references to `Iter` need to be renamed to `IntoIter`.
[breaking-change]
This is 99% burning ints to the ground, but I also got rid of useless annotations or made code more \"idiomatic\" as I went along. Mostly changes in tests.
This was particularly helpful in the time just after OIBIT's
implementation to make sure things that were supposed to be Copy
continued to be, but it's now creates a lot of noise for types that
intentionally don't want to be Copy.
r? @alexcrichton
This also removes two erroneous re-exports of the Entry variants, and so is incidentally a [breaking-change], though presumably no one should have been using those.
r? @aturon
This was particularly helpful in the time just after OIBIT's
implementation to make sure things that were supposed to be Copy
continued to be, but it's now creates a lot of noise for types that
intentionally don't want to be Copy.
Use the crates.io crate `rand` (version 0.1 should be a drop in
replacement for `std::rand`) and `rand_macros` (`#[derive_Rand]` should
be a drop-in replacement).
[breaking-change]
I’d kind of like to be able to use HashState in AnyMap, which I can’t do without a stability attribute on it. While I was at it I looked around and found a few more missing.
Now that associated types are fully implemented the iterator adaptors only need
type parameters which are associated with actual storage. All other type
parameters can either be derived from these (e.g. they are an associated type)
or can be bare on the `impl` block itself.
This is a breaking change due to the removal of type parameters on these
iterator adaptors, but code can fairly easily migrate by just deleting the
relevant type parameters for each adaptor. Other behavior should not be
affected.
Closes#21839
[breaking-change]
Now that associated types are fully implemented the iterator adaptors only need
type parameters which are associated with actual storage. All other type
parameters can either be derived from these (e.g. they are an associated type)
or can be bare on the `impl` block itself.
This is a breaking change due to the removal of type parameters on these
iterator adaptors, but code can fairly easily migrate by just deleting the
relevant type parameters for each adaptor. Other behavior should not be
affected.
Closes#21839
[breaking-change]
Not sure on what *exactly* should be said here, but I think this is the most important bit. This PR also establishes conventions for describing performance minimally.
I suggest to describe preformance for individual methods we use a `# Performance` heading. Not sure if we should have
```
# Performance: O(1)
details details
```
or
```
# Performance:
O(1)
details details
```
Since I think most methods don't need discussion, the former seems more resonable. But it's kind of weird to have info "in" the heading.
r? @steveklabnik
