::num::bigint, Remove a source of O(n^2) running time in `fn shr_bits`.
I'll cut to the chase: On my laptop, this brings the running time on
`pidigits 2000` (from src/test/bench/shootout-pidigits.rs) from this:
```
% time ./pidigits 2000 > /dev/null
real 0m7.695s
user 0m7.690s
sys 0m0.005s
```
to this:
```
% time ./pidigits 2000 > /dev/null
real 0m0.322s
user 0m0.318s
sys 0m0.004s
```
The previous code was building up a vector by repeatedly making a
fresh copy for each element that was unshifted onto the front,
yielding quadratic running time. This fixes that by building up the
vector in reverse order (pushing elements onto the end) and then
reversing it.
(Another option would be to build up a zero-initialized vector of the
desired length and then installing all of the shifted result elements
into their target index, but this was easier to hack up quickly, and
yields the desired asymptotic improvement. I have been thinking of
adding a `vec::from_fn_rev` to handle this case, maybe I will try that
this weekend.)
Externally loaded libraries are able to do things that cause references
to them to survive past the expansion phase (e.g. creating @-box cycles,
launching a task or storing something in task local data). As such, the
library has to stay loaded for the lifetime of the process.
While working on #11363 I stumbled over a couple of ignored tests, that seem to be fixed or invalid.
* src/test/run-pass/issue-3559.rs was fixed in #4726
* src/test/compile-fail/borrowck-call-sendfn.rs was fixed in #2978
* update src/test/compile-fail/issue-5500-1.rs to work with current Rust (I'm not 100% sure if the original condition is tested as mentioned in #5500, but I think so)
* removed src/test/compile-fail/issue-5500.rs because it is tested in
src/test/run-fail/issue-5500.rs (they are the same test cases, I just renamed src/test/run-fail/addr-of-bot.rs to be consistent with the other issue name
* src/test/run-pass/issue-3559.rs was fixed in #4726
* src/test/compile-fail/borrowck-call-sendfn.rs was fixed in #2978
* update src/test/compile-fail/issue-5500-1.rs to work with current Rust
* removed src/test/compile-fail/issue-5500.rs because it is tested in
src/test/run-fail/issue-5500.rs
* src/test/compile-fail/view-items-at-top.rs fixed
* #897 fixed
* compile-fail/issue-6762.rs issue was closed as dup of #6801
* deleted compile-fail/issue-2074.rs because it became irelevant and is
irrelevant #2074, a test covering this was added in
4f92f452bd
This adopts the rules posted in #10432:
1. If a seek position is negative, then an error is generated
2. Seeks beyond the end-of-file are allowed. Future writes will fill the gap
with data and future reads will return errors.
3. Seeks within the bounds of a file are fine.
Closes#10432
Cleans up a few issues with `fourcc`:
* Corrects the endianness in the docs example
* Removes `#[cfg(not(test))]` (bors might not build this on Windows. If the build fails, I'll re-add it)
* Adds a FIXME referencing the LLVM assert issue we encountered with bors builds on Windows (Same error as #10872)
Loadable syntax extensions don't work when cross compiling (see #12102), so the
fourcc tests all need to be ignored. They're valuable tests, so they shouldn't
be outright ignored, so they're now flagged with ignore-cross-compile
This adopts the rules posted in #10432:
1. If a seek position is negative, then an error is generated
2. Seeks beyond the end-of-file are allowed. Future writes will fill the gap
with data and future reads will return errors.
3. Seeks within the bounds of a file are fine.
Closes#10432
The user-facing API-level change of this commit is that `SharedChan` is gone and `Chan` now has `clone`. The major parts of this patch are the internals which have changed.
Channels are now internally upgraded from oneshots to streams to shared channels depending on the use case. I've noticed a 3x improvement in the oneshot case and very little slowdown (if any) in the stream/shared case.
This patch is mostly a reorganization of the `std::comm` module, and the large increase in code is from either dispatching to one of 3 impls or the duplication between the stream/shared impl (because they're not entirely separate).
The `comm` module is now divided into `oneshot`, `stream`, `shared`, and `select` modules. Each module contains the implementation for that flavor of channel (or the select implementation for select).
Some notable parts of this patch
* Upgrades are done through a semi-ad-hoc scheme for oneshots and messages for streams
* Upgrades are processed ASAP and have some interesting interactions with select
* send_deferred is gone because I expect the mutex to land before this
* Some of stream/shared is straight-up duplicated, but I like having the distinction between the two modules
* Select got a little worse, but it's still "basically limping along"
* This lumps in the patch of deallocating the queue backlog on packet drop
* I'll rebase this on top of the "more errors from try_recv" patch once it lands (all the infrastructure is here already)
All in all, this shouldn't be merged until the new mutexes are merged (because send_deferred wasn't implemented).
Closes#11351
This is an attempt to remove some more of Rust's dependencies on libgcc and replace it with LLVM's compiler-rt lib. I've added compiler-rt as a submodule and changed libstd to link with it.
As far as I could verify, after this change, the only symbols still imported by std from libgcc are the stack unwinding functions. Other crates, however, still picked up symbols from libgcc, not from libstd, as I had hoped. So linking definitely requires some work.
I've only tested this on windows, 32-bit linux and android and fully expect it to fail on other platforms. Patches are welcome.
This, the Nth rewrite of channels, is not a rewrite of the core logic behind
channels, but rather their API usage. In the past, we had the distinction
between oneshot, stream, and shared channels, but the most recent rewrite
dropped oneshots in favor of streams and shared channels.
This distinction of stream vs shared has shown that it's not quite what we'd
like either, and this moves the `std::comm` module in the direction of "one
channel to rule them all". There now remains only one Chan and one Port.
This new channel is actually a hybrid oneshot/stream/shared channel under the
hood in order to optimize for the use cases in question. Additionally, this also
reduces the cognitive burden of having to choose between a Chan or a SharedChan
in an API.
My simple benchmarks show no reduction in efficiency over the existing channels
today, and a 3x improvement in the oneshot case. I sadly don't have a
pre-last-rewrite compiler to test out the old old oneshots, but I would imagine
that the performance is comparable, but slightly slower (due to atomic reference
counting).
This commit also brings the bonus bugfix to channels that the pending queue of
messages are all dropped when a Port disappears rather then when both the Port
and the Chan disappear.
Beforehand, using a concurrent queue always mandated that the "shared state" be
stored internally to the queues in order to provide a safe interface. This isn't
quite as flexible as one would want in some circumstances, so instead this
commit moves the queues to not containing the shared state.
The queues no longer have a "default useful safe" interface, but rather a
"default safe" interface (minus the useful part). The queues have to be shared
manually through an Arc or some other means. This allows them to be a little
more flexible at the cost of a usability hindrance.
I plan on using this new flexibility to upgrade a channel to a shared channel
seamlessly.
I implemented an add method for the btree in progress. It is intended to be refactored later using an alternative to .clone() that passes the borrow checker, but for now, it works as intended. r? @catamorphism
I factored the commits by affected files, for the most part. The last 7 or 8 contain the meat of the PR. The rest are small changes to closures found in the codebase. Maybe interesting to read to see some of the impact of the rules.
r? @pcwalton
Fixes#6801
