fmt::Show is for debugging, and can and should be implemented for
all public types. This trait is used with `{:?}` syntax. There still
exists #[derive(Show)].
fmt::String is for types that faithfully be represented as a String.
Because of this, there is no way to derive fmt::String, all
implementations must be purposeful. It is used by the default format
syntax, `{}`.
This will break most instances of `{}`, since that now requires the type
to impl fmt::String. In most cases, replacing `{}` with `{:?}` is the
correct fix. Types that were being printed specifically for users should
receive a fmt::String implementation to fix this.
Part of #20013
[breaking-change]
parameters on impls must now also appear in the trait ref, self type,
or some associated type declared on the impl. This ensures that they
are constrianed in some way and that the semantics of the trait system
are well-defined (always a good thing).
There are three major ways to fix this error:
1. Convert the trait to use associated types; most often the type
parameters are not constrained because they are in fact outputs of
the impl.
2. Move the type parameters to methods.
3. Add an additional type parameter to the self type or trait so that
the unused parameter can appear there.
In some cases, it is not possible to fix the impl because the trait
definition needs to be changed first (and that may be out of your
control). In that case, for the time being, you can opt out of these
rules by using `#[old_impl_check]` on the impl and adding a
`#![feature(old_impl_check)]` to your crate declaration.
There's been some debate over the precise form that these APIs should take, and
they've undergone some changes recently, so these APIs are going to be left
unstable for now to be fleshed out during the next release cycle.
Both FreeBSD and DragonFly define pthread_key_t as int, while Linux
defines it as uint. As pthread_key_t is used as an opaque type and
storage size of both int and uint are the same, this is rather a
cosmetic change.
iOS uses ulong (as OS X) so difference is critical on 64bit platforms.
Believe or not, `CreateProcess()` is racy if several threads create
child processes: [0], [1], [2].
This caused some tests show crash dialogs during
`make check-stage#-rpass`.
More explanation:
On Windows, `SetErrorMode()` controls display of error dialogs: it
accepts new error mode and returns old error mode.
The error mode is process-global and automatically inherited to child
process when created.
MSYS2 bash shell internally sets it to not show error dialogs, therefore
`make check-stage#-rpass` should not show them either.
However, [1] says that `CreateProcess()` internally invokes
`SetErrorMode()` twice: at first it sets mode `0x8001` and saves
original mode, and at second it restores original mode.
So if two threads simultaneously call `CreateProcess()`, the first
thread sets error mode to `0x8001` then the second thread recognizes
that current error mode is `0x8001`. Therefore, The second thread will
create process with wrong error mode.
This really occurs inside `compiletest`: it creates several processes on
each thread, so some `run-pass` tests are invoked with wrong error mode
therefore show crash dialog.
This commit adds `StaticMutex` for `CreateProcess()` call. This seems
to fix the "dialog annoyance" issue.
[0]: http://support.microsoft.com/kb/315939
[1]: https://code.google.com/p/nativeclient/issues/detail?id=2968
[2]: https://ghc.haskell.org/trac/ghc/ticket/2650
This commit is a first past stabilization of `std::error`:
* The module is stable.
* The `FromError` trait and impls are stable
* The `Error` trait itself is left unstable, pending current APIs and
possible revisions during the alpha cycle.
This commit takes a first pass at stabilizing `std::thread`:
* It removes the `detach` method in favor of two constructors -- `spawn`
for detached threads, `scoped` for "scoped" (i.e., must-join)
threads. This addresses some of the surprise/frustrating debug
sessions with the previous API, in which `spawn` produced a guard that
on destruction joined the thread (unless `detach` was called).
The reason to have the division in part is that `Send` will soon not
imply `'static`, which means that `scoped` thread creation can take a
closure over *shared stack data* of the parent thread. On the other
hand, this means that the parent must not pop the relevant stack
frames while the child thread is running. The `JoinGuard` is used to
prevent this from happening by joining on drop (if you have not
already explicitly `join`ed.) The APIs around `scoped` are
future-proofed for the `Send` changes by taking an additional lifetime
parameter. With the current definition of `Send`, this is forced to be
`'static`, but when `Send` changes these APIs will gain their full
flexibility immediately.
Threads that are `spawn`ed, on the other hand, are detached from the
start and do not yield an RAII guard.
The hope is that, by making `scoped` an explicit opt-in with a very
suggestive name, it will be drastically less likely to be caught by a
surprising deadlock due to an implicit join at the end of a scope.
* The module itself is marked stable.
* Existing methods other than `spawn` and `scoped` are marked stable.
The migration path is:
```rust
Thread::spawn(f).detached()
```
becomes
```rust
Thread::spawn(f)
```
while
```rust
let res = Thread::spawn(f);
res.join()
```
becomes
```rust
let res = Thread::scoped(f);
res.join()
```
[breaking-change]
See RFC 550 (https://github.com/rust-lang/rfcs/pull/550) for the motivation
and details.
If this breaks your code, add one of the listed tokens after the relevant
non-terminal in your matcher.
[breaking-change]
This warning has been around in the compiler for quite some time now, but the
real place for a warning like this, if it should exist, is in Cargo, not in the
compiler itself. It's a first-class feature of Cargo that multiple versions of a
crate can be compiled into the same executable, and we shouldn't be warning
about our first-class features.
This warning has been around in the compiler for quite some time now, but the
real place for a warning like this, if it should exist, is in Cargo, not in the
compiler itself. It's a first-class feature of Cargo that multiple versions of a
crate can be compiled into the same executable, and we shouldn't be warning
about our first-class features.
cc #19260
Open questions:
- I still feel weird about marking functions like `exp` as `#[stable]` in `core` since they're highly likely to call into libm which is theoretically something core is designed to avoid and so we may be forced/want to move it at some point in the future, and so it feels like a lie to call it `#[stable]` (I know `core` is `#[experimental]`, but still...)
- `abs_sub` is a horrible name IMO: it feels like it is `(a - b).abs()`, but it is actually `(a - b).max(0.)`. maybe something along the lines of `pos_diff` ("positive difference") is better.
- the associated-function nature of `Int::from_be` and `Int::from_le` feel strange to me, it feels like they should be methods, but I cannot think of a good name.
I'm also not hugely in favour of `ldexp` and `frexp` but the precedent from C is large. (e.g. AFAICT, `ldexp` must mean "load exponent" which is essentially what it does... but only for a subset of its inputs.)
`FloatMath` no longer exists and all functionality from both traits is
available under `Float`. Change from
use std::num::{Float, FloatMath};
to
use std::num::Float;
[breaking-change]
