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Auto merge of #38214 - GuillaumeGomez:rollup, r=GuillaumeGomez
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Rollup of 9 pull requests

- Successful merges: #38085, #38123, #38151, #38153, #38158, #38163, #38186, #38189, #38208
- Failed merges:
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bors committed Dec 7, 2016
2 parents 2093084 + ef45ec0 commit 535b6d3
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23 changes: 14 additions & 9 deletions src/doc/book/ffi.md
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Expand Up @@ -662,26 +662,31 @@ attribute turns off Rust's name mangling, so that it is easier to link to.

It’s important to be mindful of `panic!`s when working with FFI. A `panic!`
across an FFI boundary is undefined behavior. If you’re writing code that may
panic, you should run it in another thread, so that the panic doesn’t bubble up
to C:
panic, you should run it in a closure with [`catch_unwind()`]:

```rust
use std::thread;
use std::panic::catch_unwind;

#[no_mangle]
pub extern fn oh_no() -> i32 {
let h = thread::spawn(|| {
let result = catch_unwind(|| {
panic!("Oops!");
});

match h.join() {
Ok(_) => 1,
Err(_) => 0,
match result {
Ok(_) => 0,
Err(_) => 1,
}
}
# fn main() {}

fn main() {}
```

Please note that [`catch_unwind()`] will only catch unwinding panics, not
those who abort the process. See the documentation of [`catch_unwind()`]
for more information.

[`catch_unwind()`]: https://doc.rust-lang.org/std/panic/fn.catch_unwind.html

# Representing opaque structs

Sometimes, a C library wants to provide a pointer to something, but not let you
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3 changes: 2 additions & 1 deletion src/doc/reference.md
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Expand Up @@ -603,7 +603,8 @@ syntax named by _designator_. Valid designators are:
* `ty`: a [type](#types)
* `ident`: an [identifier](#identifiers)
* `path`: a [path](#paths)
* `tt`: either side of the `=>` in macro rules
* `tt`: a token tree (a single [token](#tokens) or a sequence of token trees surrounded
by matching `()`, `[]`, or `{}`)
* `meta`: the contents of an [attribute](#attributes)

In the transcriber, the
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88 changes: 45 additions & 43 deletions src/liballoc/rc.rs
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Expand Up @@ -12,35 +12,35 @@

//! Single-threaded reference-counting pointers.
//!
//! The type [`Rc<T>`][rc] provides shared ownership of a value of type `T`,
//! allocated in the heap. Invoking [`clone`][clone] on `Rc` produces a new
//! pointer to the same value in the heap. When the last `Rc` pointer to a
//! The type [`Rc<T>`][`Rc`] provides shared ownership of a value of type `T`,
//! allocated in the heap. Invoking [`clone()`][clone] on [`Rc`] produces a new
//! pointer to the same value in the heap. When the last [`Rc`] pointer to a
//! given value is destroyed, the pointed-to value is also destroyed.
//!
//! Shared references in Rust disallow mutation by default, and `Rc` is no
//! exception. If you need to mutate through an `Rc`, use [`Cell`][cell] or
//! [`RefCell`][refcell].
//! exception. If you need to mutate through an [`Rc`], use [`Cell`] or
//! [`RefCell`].
//!
//! `Rc` uses non-atomic reference counting. This means that overhead is very
//! low, but an `Rc` cannot be sent between threads, and consequently `Rc`
//! [`Rc`] uses non-atomic reference counting. This means that overhead is very
//! low, but an [`Rc`] cannot be sent between threads, and consequently [`Rc`]
//! does not implement [`Send`][send]. As a result, the Rust compiler
//! will check *at compile time* that you are not sending `Rc`s between
//! will check *at compile time* that you are not sending [`Rc`]s between
//! threads. If you need multi-threaded, atomic reference counting, use
//! [`sync::Arc`][arc].
//!
//! The [`downgrade`][downgrade] method can be used to create a non-owning
//! [`Weak`][weak] pointer. A `Weak` pointer can be [`upgrade`][upgrade]d
//! to an `Rc`, but this will return [`None`][option] if the value has
//! The [`downgrade()`][downgrade] method can be used to create a non-owning
//! [`Weak`] pointer. A [`Weak`] pointer can be [`upgrade`][upgrade]d
//! to an [`Rc`], but this will return [`None`] if the value has
//! already been dropped.
//!
//! A cycle between `Rc` pointers will never be deallocated. For this reason,
//! `Weak` is used to break cycles. For example, a tree could have strong
//! `Rc` pointers from parent nodes to children, and `Weak` pointers from
//! A cycle between [`Rc`] pointers will never be deallocated. For this reason,
//! [`Weak`] is used to break cycles. For example, a tree could have strong
//! [`Rc`] pointers from parent nodes to children, and [`Weak`] pointers from
//! children back to their parents.
//!
//! `Rc<T>` automatically dereferences to `T` (via the [`Deref`][deref] trait),
//! so you can call `T`'s methods on a value of type `Rc<T>`. To avoid name
//! clashes with `T`'s methods, the methods of `Rc<T>` itself are [associated
//! `Rc<T>` automatically dereferences to `T` (via the [`Deref`] trait),
//! so you can call `T`'s methods on a value of type [`Rc<T>`][`Rc`]. To avoid name
//! clashes with `T`'s methods, the methods of [`Rc<T>`][`Rc`] itself are [associated
//! functions][assoc], called using function-like syntax:
//!
//! ```
Expand All @@ -50,28 +50,15 @@
//! Rc::downgrade(&my_rc);
//! ```
//!
//! `Weak<T>` does not auto-dereference to `T`, because the value may have
//! [`Weak<T>`][`Weak`] does not auto-dereference to `T`, because the value may have
//! already been destroyed.
//!
//! [rc]: struct.Rc.html
//! [weak]: struct.Weak.html
//! [clone]: ../../std/clone/trait.Clone.html#tymethod.clone
//! [cell]: ../../std/cell/struct.Cell.html
//! [refcell]: ../../std/cell/struct.RefCell.html
//! [send]: ../../std/marker/trait.Send.html
//! [arc]: ../../std/sync/struct.Arc.html
//! [deref]: ../../std/ops/trait.Deref.html
//! [downgrade]: struct.Rc.html#method.downgrade
//! [upgrade]: struct.Weak.html#method.upgrade
//! [option]: ../../std/option/enum.Option.html
//! [assoc]: ../../book/method-syntax.html#associated-functions
//!
//! # Examples
//!
//! Consider a scenario where a set of `Gadget`s are owned by a given `Owner`.
//! We want to have our `Gadget`s point to their `Owner`. We can't do this with
//! unique ownership, because more than one gadget may belong to the same
//! `Owner`. `Rc` allows us to share an `Owner` between multiple `Gadget`s,
//! `Owner`. [`Rc`] allows us to share an `Owner` between multiple `Gadget`s,
//! and have the `Owner` remain allocated as long as any `Gadget` points at it.
//!
//! ```
Expand Down Expand Up @@ -127,20 +114,20 @@
//! ```
//!
//! If our requirements change, and we also need to be able to traverse from
//! `Owner` to `Gadget`, we will run into problems. An `Rc` pointer from `Owner`
//! `Owner` to `Gadget`, we will run into problems. An [`Rc`] pointer from `Owner`
//! to `Gadget` introduces a cycle between the values. This means that their
//! reference counts can never reach 0, and the values will remain allocated
//! forever: a memory leak. In order to get around this, we can use `Weak`
//! forever: a memory leak. In order to get around this, we can use [`Weak`]
//! pointers.
//!
//! Rust actually makes it somewhat difficult to produce this loop in the first
//! place. In order to end up with two values that point at each other, one of
//! them needs to be mutable. This is difficult because `Rc` enforces
//! them needs to be mutable. This is difficult because [`Rc`] enforces
//! memory safety by only giving out shared references to the value it wraps,
//! and these don't allow direct mutation. We need to wrap the part of the
//! value we wish to mutate in a [`RefCell`][refcell], which provides *interior
//! value we wish to mutate in a [`RefCell`], which provides *interior
//! mutability*: a method to achieve mutability through a shared reference.
//! `RefCell` enforces Rust's borrowing rules at runtime.
//! [`RefCell`] enforces Rust's borrowing rules at runtime.
//!
//! ```
//! use std::rc::Rc;
Expand Down Expand Up @@ -214,6 +201,19 @@
//! // Gadget Man, so he gets destroyed as well.
//! }
//! ```
//!
//! [`Rc`]: struct.Rc.html
//! [`Weak`]: struct.Weak.html
//! [clone]: ../../std/clone/trait.Clone.html#tymethod.clone
//! [`Cell`]: ../../std/cell/struct.Cell.html
//! [`RefCell`]: ../../std/cell/struct.RefCell.html
//! [send]: ../../std/marker/trait.Send.html
//! [arc]: ../../std/sync/struct.Arc.html
//! [`Deref`]: ../../std/ops/trait.Deref.html
//! [downgrade]: struct.Rc.html#method.downgrade
//! [upgrade]: struct.Weak.html#method.upgrade
//! [`None`]: ../../std/option/enum.Option.html#variant.None
//! [assoc]: ../../book/method-syntax.html#associated-functions

#![stable(feature = "rust1", since = "1.0.0")]

Expand Down Expand Up @@ -251,9 +251,11 @@ struct RcBox<T: ?Sized> {
/// See the [module-level documentation](./index.html) for more details.
///
/// The inherent methods of `Rc` are all associated functions, which means
/// that you have to call them as e.g. `Rc::get_mut(&value)` instead of
/// `value.get_mut()`. This avoids conflicts with methods of the inner
/// that you have to call them as e.g. [`Rc::get_mut(&value)`][get_mut] instead of
/// `value.get_mut()`. This avoids conflicts with methods of the inner
/// type `T`.
///
/// [get_mut]: #method.get_mut
#[stable(feature = "rust1", since = "1.0.0")]
pub struct Rc<T: ?Sized> {
ptr: Shared<RcBox<T>>,
Expand Down Expand Up @@ -337,10 +339,10 @@ impl<T> Rc<T> {
}

/// Checks whether [`Rc::try_unwrap`][try_unwrap] would return
/// [`Ok`][result].
/// [`Ok`].
///
/// [try_unwrap]: struct.Rc.html#method.try_unwrap
/// [result]: ../../std/result/enum.Result.html
/// [`Ok`]: ../../std/result/enum.Result.html#variant.Ok
///
/// # Examples
///
Expand Down Expand Up @@ -543,14 +545,14 @@ impl<T: ?Sized> Rc<T> {
/// Returns a mutable reference to the inner value, if there are
/// no other `Rc` or [`Weak`][weak] pointers to the same value.
///
/// Returns [`None`][option] otherwise, because it is not safe to
/// Returns [`None`] otherwise, because it is not safe to
/// mutate a shared value.
///
/// See also [`make_mut`][make_mut], which will [`clone`][clone]
/// the inner value when it's shared.
///
/// [weak]: struct.Weak.html
/// [option]: ../../std/option/enum.Option.html
/// [`None`]: ../../std/option/enum.Option.html#variant.None
/// [make_mut]: struct.Rc.html#method.make_mut
/// [clone]: ../../std/clone/trait.Clone.html#tymethod.clone
///
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6 changes: 6 additions & 0 deletions src/librustc_resolve/check_unused.rs
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Expand Up @@ -103,6 +103,12 @@ impl<'a, 'b> Visitor for UnusedImportCheckVisitor<'a, 'b> {
}

ViewPathList(_, ref list) => {
if list.len() == 0 {
self.unused_imports
.entry(item.id)
.or_insert_with(NodeMap)
.insert(item.id, item.span);
}
for i in list {
self.check_import(item.id, i.node.id, i.span);
}
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4 changes: 4 additions & 0 deletions src/libstd/collections/hash/map.rs
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Expand Up @@ -2117,6 +2117,10 @@ impl DefaultHasher {

#[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
impl Default for DefaultHasher {
/// Creates a new `DefaultHasher` using [`DefaultHasher::new`]. See
/// [`DefaultHasher::new`] documentation for more information.
///
/// [`DefaultHasher::new`]: #method.new
fn default() -> DefaultHasher {
DefaultHasher::new()
}
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106 changes: 104 additions & 2 deletions src/libstd/panicking.rs
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Expand Up @@ -159,6 +159,23 @@ pub fn take_hook() -> Box<Fn(&PanicInfo) + 'static + Sync + Send> {
}

/// A struct providing information about a panic.
///
/// `PanicInfo` structure is passed to a panic hook set by the [`set_hook()`]
/// function.
///
/// [`set_hook()`]: ../../std/panic/fn.set_hook.html
///
/// # Examples
///
/// ```should_panic
/// use std::panic;
///
/// panic::set_hook(Box::new(|panic_info| {
/// println!("panic occured: {:?}", panic_info.payload().downcast_ref::<&str>().unwrap());
/// }));
///
/// panic!("Normal panic");
/// ```
#[stable(feature = "panic_hooks", since = "1.10.0")]
pub struct PanicInfo<'a> {
payload: &'a (Any + Send),
Expand All @@ -168,7 +185,21 @@ pub struct PanicInfo<'a> {
impl<'a> PanicInfo<'a> {
/// Returns the payload associated with the panic.
///
/// This will commonly, but not always, be a `&'static str` or `String`.
/// This will commonly, but not always, be a `&'static str` or [`String`].
///
/// [`String`]: ../../std/string/struct.String.html
///
/// # Examples
///
/// ```should_panic
/// use std::panic;
///
/// panic::set_hook(Box::new(|panic_info| {
/// println!("panic occured: {:?}", panic_info.payload().downcast_ref::<&str>().unwrap());
/// }));
///
/// panic!("Normal panic");
/// ```
#[stable(feature = "panic_hooks", since = "1.10.0")]
pub fn payload(&self) -> &(Any + Send) {
self.payload
Expand All @@ -177,15 +208,54 @@ impl<'a> PanicInfo<'a> {
/// Returns information about the location from which the panic originated,
/// if available.
///
/// This method will currently always return `Some`, but this may change
/// This method will currently always return [`Some`], but this may change
/// in future versions.
///
/// [`Some`]: ../../std/option/enum.Option.html#variant.Some
///
/// # Examples
///
/// ```should_panic
/// use std::panic;
///
/// panic::set_hook(Box::new(|panic_info| {
/// if let Some(location) = panic_info.location() {
/// println!("panic occured in file '{}' at line {}", location.file(), location.line());
/// } else {
/// println!("panic occured but can't get location information...");
/// }
/// }));
///
/// panic!("Normal panic");
/// ```
#[stable(feature = "panic_hooks", since = "1.10.0")]
pub fn location(&self) -> Option<&Location> {
Some(&self.location)
}
}

/// A struct containing information about the location of a panic.
///
/// This structure is created by the [`location()`] method of [`PanicInfo`].
///
/// [`location()`]: ../../std/panic/struct.PanicInfo.html#method.location
/// [`PanicInfo`]: ../../std/panic/struct.PanicInfo.html
///
/// # Examples
///
/// ```should_panic
/// use std::panic;
///
/// panic::set_hook(Box::new(|panic_info| {
/// if let Some(location) = panic_info.location() {
/// println!("panic occured in file '{}' at line {}", location.file(), location.line());
/// } else {
/// println!("panic occured but can't get location information...");
/// }
/// }));
///
/// panic!("Normal panic");
/// ```
#[stable(feature = "panic_hooks", since = "1.10.0")]
pub struct Location<'a> {
file: &'a str,
Expand All @@ -194,12 +264,44 @@ pub struct Location<'a> {

impl<'a> Location<'a> {
/// Returns the name of the source file from which the panic originated.
///
/// # Examples
///
/// ```should_panic
/// use std::panic;
///
/// panic::set_hook(Box::new(|panic_info| {
/// if let Some(location) = panic_info.location() {
/// println!("panic occured in file '{}'", location.file());
/// } else {
/// println!("panic occured but can't get location information...");
/// }
/// }));
///
/// panic!("Normal panic");
/// ```
#[stable(feature = "panic_hooks", since = "1.10.0")]
pub fn file(&self) -> &str {
self.file
}

/// Returns the line number from which the panic originated.
///
/// # Examples
///
/// ```should_panic
/// use std::panic;
///
/// panic::set_hook(Box::new(|panic_info| {
/// if let Some(location) = panic_info.location() {
/// println!("panic occured at line {}", location.line());
/// } else {
/// println!("panic occured but can't get location information...");
/// }
/// }));
///
/// panic!("Normal panic");
/// ```
#[stable(feature = "panic_hooks", since = "1.10.0")]
pub fn line(&self) -> u32 {
self.line
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