`Times::times` was always a second-class loop because it did not support the `break` and `continue` operations. Its playful appeal (which I liked) was then lost after `do` was disabled for closures. It's time to let this one go.
`Times::times` was always a second-class loop because it did not support the `break` and `continue` operations. Its playful appeal was then lost after `do` was disabled for closures. It's time to let this one go.
I found awkward to have `MutableCloneableVector` and `CloneableIterator` on the one hand, and `CopyableVector` etc. on the other hand.
The concerned traits are:
* `CopyableVector` --> `CloneableVector`
* `OwnedCopyableVector` --> `OwnedCloneableVector`
* `ImmutableCopyableVector` --> `ImmutableCloneableVector`
* `CopyableTuple` --> `CloneableTuple`
The general consensus is that we want to move away from conditions for I/O, and I propose a two-step plan for doing so:
1. Warn about unused `Result` types. When all of I/O returns `Result`, it will require you inspect the return value for an error *only if* you have a result you want to look at. By default, for things like `write` returning `Result<(), Error>`, these will all go silently ignored. This lint will prevent blind ignorance of these return values, letting you know that there's something you should do about them.
2. Implement a `try!` macro:
```
macro_rules! try( ($e:expr) => (match $e { Ok(e) => e, Err(e) => return Err(e) }) )
```
With these two tools combined, I feel that we get almost all the benefits of conditions. The first step (the lint) is a sanity check that you're not ignoring return values at callsites. The second step is to provide a convenience method of returning early out of a sequence of computations. After thinking about this for awhile, I don't think that we need the so-called "do-notation" in the compiler itself because I think it's just *too* specialized. Additionally, the `try!` macro is super lightweight, easy to understand, and works almost everywhere. As soon as you want to do something more fancy, my answer is "use match".
Basically, with these two tools in action, I would be comfortable removing conditions. What do others think about this strategy?
----
This PR specifically implements the `unused_result` lint. I actually added two lints, `unused_result` and `unused_must_use`, and the first commit has the rationale for why `unused_result` is turned off by default.
These are either returned from public functions, and really should
appear in the documentation, but don't since they're private, or are
implementation details that are currently public.
These are either returned from public functions, and really should
appear in the documentation, but don't since they're private, or are
implementation details that are currently public.
Native timers are a much hairier thing to deal with than green timers due to the
interface that we would like to expose (both a blocking sleep() and a
channel-based interface). I ended up implementing timers in three different ways
for the various platforms that we supports.
In all three of the implementations, there is a worker thread which does send()s
on channels for timers. This worker thread is initialized once and then
communicated to in a platform-specific manner, but there's always a shared
channel available for sending messages to the worker thread.
* Windows - I decided to use windows kernel timer objects via
CreateWaitableTimer and SetWaitableTimer in order to provide sleeping
capabilities. The worker thread blocks via WaitForMultipleObjects where one of
the objects is an event that is used to wake up the helper thread (which then
drains the incoming message channel for requests).
* Linux/(Android?) - These have the ideal interface for implementing timers,
timerfd_create. Each timer corresponds to a timerfd, and the helper thread
uses epoll to wait for all active timers and then send() for the next one that
wakes up. The tricky part in this implementation is updating a timerfd, but
see the implementation for the fun details
* OSX/FreeBSD - These obviously don't have the windows APIs, and sadly don't
have the timerfd api available to them, so I have thrown together a solution
which uses select() plus a timeout in order to ad-hoc-ly implement a timer
solution for threads. The implementation is backed by a sorted array of timers
which need to fire. As I said, this is an ad-hoc solution which is certainly
not accurate timing-wise. I have done this implementation due to the lack of
other primitives to provide an implementation, and I've done it the best that
I could, but I'm sure that there's room for improvement.
I'm pretty happy with how these implementations turned out. In theory we could
drop the timerfd implementation and have linux use the select() + timeout
implementation, but it's so inaccurate that I would much rather continue to use
timerfd rather than my ad-hoc select() implementation.
The only change that I would make to the API in general is to have a generic
sleep() method on an IoFactory which doesn't require allocating a Timer object.
For everything but windows it's super-cheap to request a blocking sleep for a
set amount of time, and it's probably worth it to provide a sleep() which
doesn't do something like allocate a file descriptor on linux.
* Reexport io::mem and io::buffered structs directly under io, make mem/buffered
private modules
* Remove with_mem_writer
* Remove DEFAULT_CAPACITY and use DEFAULT_BUF_SIZE (in io::buffered)
cc #11119
* Reexport io::mem and io::buffered structs directly under io, make mem/buffered
private modules
* Remove with_mem_writer
* Remove DEFAULT_CAPACITY and use DEFAULT_BUF_SIZE (in io::buffered)
Major changes:
- Define temporary scopes in a syntax-based way that basically defaults
to the innermost statement or conditional block, except for in
a `let` initializer, where we default to the innermost block. Rules
are documented in the code, but not in the manual (yet).
See new test run-pass/cleanup-value-scopes.rs for examples.
- Refactors Datum to better define cleanup roles.
- Refactor cleanup scopes to not be tied to basic blocks, permitting
us to have a very large number of scopes (one per AST node).
- Introduce nascent documentation in trans/doc.rs covering datums and
cleanup in a more comprehensive way.
The `print!` and `println!` macros are now the preferred method of printing, and so there is no reason to export the `stdio` functions in the prelude. The functions have also been replaced by their macro counterparts in the tutorial and other documentation so that newcomers don't get confused about what they should be using.
The `print!` and `println!` macros are now the preferred method of printing, and so there is no reason to export the `stdio` functions in the prelude. The functions have also been replaced by their macro counterparts in the tutorial and other documentation so that newcomers don't get confused about what they should be using.
Instead of reading a byte at a time in a loop we copy the relevant bytes into
a temporary vector of size eight. We can then read the value from the temporary
vector using a single u64 read. LLVM seems to be able to optimize this
almost scarily good.
This is just an unnecessary trait that no one's ever going to parameterize over
and it's more useful to just define the methods directly on the types
themselves. The implementors of this type almost always don't want
inner_mut_ref() but they're forced to define it as well.
This will allow capturing of common things like logging messages, stdout prints
(using stdio println), and failure messages (printed to stderr). Any new prints
added to libstd should be funneled through these task handles to allow capture
as well.
Additionally, this commit redirects logging back through a `Logger` trait so the
log level can be usefully consumed by an arbitrary logger.
This commit also introduces methods to set the task-local stdout handles:
* std::io::stdio::set_stdout
* std::io::stdio::set_stderr
* std::io::logging::set_logger
These methods all return the previous logger just in case it needs to be used
for inspection.
I plan on using this infrastructure for extra::test soon, but we don't quite
have the primitives that I'd like to use for it, so it doesn't migrate
extra::test at this time.
Closes#6369
Similarly to the recent commit to do this for networking, there's no reason that
a read on a file descriptor should continue reading until the entire buffer is
full. This makes sense when dealing with literal files, but when dealing with
things like stdin this doesn't make sense.
