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Simplify output capturing
This is a sequence of incremental improvements to the unstable/internal `set_panic` and `set_print` mechanism used by the `test` crate:
1. Remove the `LocalOutput` trait and use `Arc<Mutex<dyn Write>>` instead of `Box<dyn LocalOutput>`. In practice, all implementations of `LocalOutput` were just `Arc<Mutex<..>>`. This simplifies some logic and removes all custom `Sink` implementations such as `library/test/src/helpers/sink.rs`. Also removes a layer of indirection, as the outermost `Box` is now gone. It also means that locking now happens per `write_fmt`, not per individual `write` within. (So `"{} {}\n"` now results in one `lock()`, not four or more.)
2. Since in all cases the `dyn Write`s were just `Vec<u8>`s, replace the type with `Arc<Mutex<Vec<u8>>>`. This simplifies things more, as error handling and flushing can be removed now. This also removes the hack needed in the default panic handler to make this work with `::realstd`, as (unlike `Write`) `Vec<u8>` is from `alloc`, not `std`.
3. Replace the `RefCell`s by regular `Cell`s. The `RefCell`s were mostly used as `mem::replace(&mut *cell.borrow_mut(), something)`, which is just `Cell::replace`. This removes an unecessary bookkeeping and makes the code a bit easier to read.
4. Merge `set_panic` and `set_print` into a single `set_output_capture`. Neither the test crate nor rustc (the only users of this feature) have a use for using these separately. Merging them simplifies things even more. This uses a new function name and feature name, to make it clearer this is internal and not supposed to be used by other crates.
Might be easier to review per commit.
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Remove all rustc-link-lib from the std build script. Also remove use of
feature = "restricted-std" where not necessary.
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specialize io::copy to use copy_file_range, splice or sendfile
Fixes #74426.
Also covers #60689 but only as an optimization instead of an official API.
The specialization only covers std-owned structs so it should avoid the problems with #71091
Currently linux-only but it should be generalizable to other unix systems that have sendfile/sosplice and similar.
There is a bit of optimization potential around the syscall count. Right now it may end up doing more syscalls than the naive copy loop when doing short (<8KiB) copies between file descriptors.
The test case executes the following:
```
[pid 103776] statx(3, "", AT_STATX_SYNC_AS_STAT|AT_EMPTY_PATH, STATX_ALL, {stx_mask=STATX_ALL|STATX_MNT_ID, stx_attributes=0, stx_mode=S_IFREG|0644, stx_size=17, ...}) = 0
[pid 103776] write(4, "wxyz", 4) = 4
[pid 103776] write(4, "iklmn", 5) = 5
[pid 103776] copy_file_range(3, NULL, 4, NULL, 5, 0) = 5
```
0-1 `stat` calls to identify the source file type. 0 if the type can be inferred from the struct from which the FD was extracted
𝖬 `write` to drain the `BufReader`/`BufWriter` wrappers. only happen when buffers are present. 𝖬 ≾ number of wrappers present. If there is a write buffer it may absorb the read buffer contents first so only result in a single write. Vectored writes would also be an option but that would require more invasive changes to `BufWriter`.
𝖭 `copy_file_range`/`splice`/`sendfile` until file size, EOF or the byte limit from `Take` is reached. This should generally be *much* more efficient than the read-write loop and also have other benefits such as DMA offload or extent sharing.
## Benchmarks
```
OLD
test io::tests::bench_file_to_file_copy ... bench: 21,002 ns/iter (+/- 750) = 6240 MB/s [ext4]
test io::tests::bench_file_to_file_copy ... bench: 35,704 ns/iter (+/- 1,108) = 3671 MB/s [btrfs]
test io::tests::bench_file_to_socket_copy ... bench: 57,002 ns/iter (+/- 4,205) = 2299 MB/s
test io::tests::bench_socket_pipe_socket_copy ... bench: 142,640 ns/iter (+/- 77,851) = 918 MB/s
NEW
test io::tests::bench_file_to_file_copy ... bench: 14,745 ns/iter (+/- 519) = 8889 MB/s [ext4]
test io::tests::bench_file_to_file_copy ... bench: 6,128 ns/iter (+/- 227) = 21389 MB/s [btrfs]
test io::tests::bench_file_to_socket_copy ... bench: 13,767 ns/iter (+/- 3,767) = 9520 MB/s
test io::tests::bench_socket_pipe_socket_copy ... bench: 26,471 ns/iter (+/- 6,412) = 4951 MB/s
```
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Currently it only applies to linux systems. It can be extended to make use
of similar syscalls on other unix systems.
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Duration::zero() -> Duration::ZERO
In review for #72790, whether or not a constant or a function should be favored for `#![feature(duration_zero)]` was seen as an open question. In https://github.com/rust-lang/rust/issues/73544#issuecomment-691701670 an invitation was opened to either stabilize the methods or propose a switch to the constant value, supplemented with reasoning. Followup comments suggested community preference leans towards the const ZERO, which would be reason enough.
ZERO also "makes sense" beside existing associated consts for Duration. It is ever so slightly awkward to have a series of constants specifying 1 of various units but leave 0 as a method, especially when they are side-by-side in code. It seems unintuitive for the one non-dynamic value (that isn't from Default) to be not-a-const, which could hurt discoverability of the associated constants overall. Elsewhere in `std`, methods for obtaining a constant value were even deprecated, as seen with [std::u32::min_value](https://doc.rust-lang.org/std/primitive.u32.html#method.min_value).
Most importantly, ZERO costs less to use. A match supports a const pattern, but const fn can only be used if evaluated through a const context such as an inline `const { const_fn() }` or a `const NAME: T = const_fn()` declaration elsewhere. Likewise, while https://github.com/rust-lang/rust/issues/73544#issuecomment-691949373 notes `Duration::zero()` can optimize to a constant value, "can" is not "will". Only const contexts have a strong promise of such. Even without that in mind, the comment in question still leans in favor of the constant for simplicity. As it costs less for a developer to use, may cost less to optimize, and seems to have more of a community consensus for it, the associated const seems best.
r? ```@LukasKalbertodt```
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There were no use cases for setting them separately.
Merging them simplifies some things.
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It was only ever used with Vec<u8> anyway. This simplifies some things.
- It no longer needs to be flushed, because that's a no-op anyway for
a Vec<u8>.
- Writing to a Vec<u8> never fails.
- No #[cfg(test)] code is needed anymore to use `realstd` instead of
`std`, because Vec comes from alloc, not std (like Write).
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Make some std::io functions `const`
Tracking issue: #78812
Make the following functions `const`:
- `io::Cursor::new`
- `io::Cursor::get_ref`
- `io::Cursor::position`
- `io::empty`
- `io::repeat`
- `io::sink`
r? `````@dtolnay`````
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Includes:
- io::Cursor::new
- io::Cursor::get_ref
- io::Cursor::position
- io::empty
- io::repeat
- io::sink
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Partially fix #55002, deprecate in another release
Co-authored-by: Ashley Mannix <kodraus@hey.com>
Update stable version for stabilize_spin_loop
Co-authored-by: Joshua Nelson <joshua@yottadb.com>
Use better example for spinlock
As suggested by KodrAus
Remove renamed_spin_loop already available in master
Fix spin loop example
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replace `#[allow_internal_unstable]` with `#[rustc_allow_const_fn_unstable]` for `const fn`s
`#[allow_internal_unstable]` is currently used to side-step feature gate and stability checks.
While it was originally only meant to be used only on macros, its use was expanded to `const fn`s.
This pr adds stricter checks for the usage of `#[allow_internal_unstable]` (only on macros) and introduces the `#[rustc_allow_const_fn_unstable]` attribute for usage on `const fn`s.
This pr does not change any of the functionality associated with the use of `#[allow_internal_unstable]` on macros or the usage of `#[rustc_allow_const_fn_unstable]` (instead of `#[allow_internal_unstable]`) on `const fn`s (see https://github.com/rust-lang/rust/issues/69399#issuecomment-712911540).
Note: The check for `#[rustc_allow_const_fn_unstable]` currently only validates that the attribute is used on a function, because I don't know how I would check if the function is a `const fn` at the place of the check. I therefore openend this as a 'draft pull request'.
Closes rust-lang/rust#69399
r? @oli-obk
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This expands time's test suite to use more and in more places the
range of methods and constants added to Duration in recent
proposals for the sake of testing more API surface area and
improving legibility.
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This makes it consistent with std::panic!("message"), which also throws
a &str, not a String.
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Link to documentation-specific guidelines.
Changed contribution information URL because it's not obvious how to get from the current URL to the documentation-specific content.
The current URL points to this "Getting Started" page, which contains nothing specific about documentation[*] and instead launches into how to *build* `rustc` which is not a strict prerequisite for contributing documentation fixes:
* https://rustc-dev-guide.rust-lang.org/getting-started.html
[*] The most specific content is a "Writing documentation" bullet point which is not itself a link to anything (I guess a patch for that might be helpful too).
### Why?
Making this change will make it easier for people who wish to make small "drive by" documentation fixes (and read contribution guidelines ;) ) which I find are often how I start contributing to a project. (Exhibit A: https://github.com/rust-lang/rust/pull/77050 :) )
### Background
My impression is the change of content linked is an unintentional change due to a couple of other changes:
* Originally, the link pointed to `contributing.md` which started with a "table of contents" linking to each section. But the content in `contributing.md` was removed and replaced with a link to the "Getting Started" section here:
* https://github.com/rust-lang/rust/commit/3f6928f1f6eff367e6ddbfb63ebc5e568ffe0eb1#diff-6a3371457528722a734f3c51d9238c13L1
But the changed link doesn't actually point to the equivalent content, which is now located here:
* https://rustc-dev-guide.rust-lang.org/contributing.html
(If the "Guide to Rustc Development" is now considered the canonical location of "How to Contribute" content it might be a good idea to merge some of the "Contributing" Introduction section into the "Getting Started" section.)
* This was then compounded by changing the link from `contributing.md` to `contributing.html` here:
* https://github.com/rust-lang/rust/pull/74037/files#diff-242481015141f373dcb178e93cffa850L88
In order to even find the new location of the previous `contributing.md` content I ended up needing to do a GitHub search of the `rust-lang` org for the phrase "Documentation improvements are very welcome". :D
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Only use LOCAL_{STDOUT,STDERR} when set_{print/panic} is used.
The thread local `LOCAL_STDOUT` and `LOCAL_STDERR` are only used by the `test` crate to capture output from tests when running them in the same process in differen threads. However, every program will check these variables on every print, even outside of testing.
This involves allocating a thread local key, and registering a thread local destructor. This can be somewhat expensive.
This change keeps a global flag (`LOCAL_STREAMS`) which will be set to `true` when either of these local streams is used. (So, effectively only in test and benchmark runs.) When this flag is off, these thread locals are not even looked at and therefore will not be initialized on the first output on every thread, which also means no thread local destructors will be registered.
---
Together with https://github.com/rust-lang/rust/pull/77154, this should make output a little bit more efficient.
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The thread local LOCAL_STDOUT and LOCAL_STDERR are only used by the test
crate to capture output from tests when running them in the same process
in differen threads. However, every program will check these variables
on every print, even outside of testing.
This involves allocating a thread local key, and registering a thread
local destructor. This can be somewhat expensive.
This change keeps a global flag (LOCAL_STREAMS) which will be set to
true when either of these local streams is used. (So, effectively only
in test and benchmark runs.) When this flag is off, these thread locals
are not even looked at and therefore will not be initialized on the
first output on every thread, which also means no thread local
destructors will be registered.
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Changed because it's not obvious how to get from the previously used URL to the documentation-specific content.
This is partly because the original URL was previously changed to point to different content:
* https://github.com/rust-lang/rust/pull/74037/files#diff-242481015141f373dcb178e93cffa850L88
* https://github.com/rust-lang/rust/commit/3f6928f1f6eff367e6ddbfb63ebc5e568ffe0eb1#diff-6a3371457528722a734f3c51d9238c13L12
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Make the following methods of `std::net::IpAddr` unstable const under the `const_ip` feature:
- `is_unspecified`
- `is_loopback`
- `is_global`
- `is_multicast`
Also adds a test for these methods in a const context.
Possible because these methods delegate to the inner `Ipv4Addr` or `Ipv6Addr`, which were made const, and the recent stabilization of const control flow.
Part of #76205
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This may not be strictly minimal, but all unstable functions also need a
`rustc_const_unstable` attribute.
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Add non-`unsafe` `.get_mut()` for `Unsafecell`
- Tracking issue: https://github.com/rust-lang/rust/issues/76943
As discussed in: https://internals.rust-lang.org/t/add-non-unsafe-get-mut-for-unsafecell/12407
- ### [Rendered documentation](https://modest-dubinsky-1f9f47.netlify.app/core/cell/struct.unsafecell)
This PR tries to move the sound `&mut UnsafeCell<T> -> &mut T` projection that all the "downstream" constructions were already relying on, up to the root abstraction, where it rightfully belongs, and officially blessing it.
- this **helps reduce the amount of `unsafe` snippets out there** (_c.f._, the second commit of this PR: https://github.com/rust-lang/rust/pull/76936/commits/09503fd1b30c83ca605546fa3f899721e41e68c6)
The fact that this getter is now expose for `UnsafeCell<T>` itself, will also help convey the idea that **`UnsafeCell` is not magical _w.r.t._ `&mut` accesses**, contrary to what some people incorrectly think.
- Even the standard library itself at some point had such a confusion, _c.f._ this comment where there is a mention of multi-threaded (and thus _shared_) access despite dealing with exclusive references over unique ownership: https://github.com/rust-lang/rust/blob/59fb88d061544a035f3043b47594b34789204cee/library/core/src/cell.rs#L498-L499
r? @RalfJung
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Remove unused feature gates from library/ crates
Removes some unused feature gates from library crates. It's likely not a complete list as I only tested a subset for which it's more likely that it is unused.
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Libc isn't used by alloc.
And std and panic_* use libc from crates.io now,
which isn't feature gated.
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Small cleanups in Windows Mutex.
- Move `held` into the boxed part, since the SRW lock implementation does not use this. This makes the Mutex 50% smaller.
- Use `Cell` instead of `UnsafeCell` for `held`, such that `.replace()` can be used.
- Add some comments.
- Avoid creating multiple `&mut`s to the critical section object in `ReentrantMutex`.
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Stabilize core::future::{pending,ready}
This PR stabilizes `core::future::{pending,ready}`, tracking issue https://github.com/rust-lang/rust/issues/70921.
## Motivation
These functions have been on nightly for three months now, and have lived as part of the futures ecosystem for several years. In that time these functions have undergone several iterations, with [the `async-std` impls](https://docs.rs/async-std/1.6.2/async_std/future/index.html) probably diverging the most (using `async fn`, which in hindsight was a mistake).
It seems the space around these functions has been _thoroughly_ explored over the last couple of years, and the ecosystem has settled on the current shape of the functions. It seems highly unlikely we'd want to make any further changes to these functions, so I propose we stabilize.
## Implementation notes
This stabilization PR was fairly straightforward; this feature has already thoroughly been reviewed by the libs team already in https://github.com/rust-lang/rust/pull/70834. So all this PR does is remove the feature gate.
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Make all methods of `std::net::Ipv4Addr` const
Make the following methods of `std::net::Ipv4Addr` unstable const under the `const_ipv4` feature:
- `octets`
- `is_loopback`
- `is_private`
- `is_link_local`
- `is_global` (unstable)
- `is_shared` (unstable)
- `is_ietf_protocol_assignment` (unstable)
- `is_benchmarking` (unstable)
- `is_reserved` (unstable)
- `is_multicast`
- `is_broadcast`
- `is_documentation`
- `to_ipv6_compatible`
- `to_ipv6_mapped`
This would make all methods of `Ipv6Addr` const.
Of these methods, `is_global`, `is_broadcast`, `to_ipv6_compatible`, and `to_ipv6_mapped` require a change in implementation.
Part of #76205
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Make the following methods of `std::net::Ipv6Addr` unstable const under the `const_ipv6` feature:
- `segments`
- `is_unspecified`
- `is_loopback`
- `is_global` (unstable)
- `is_unique_local`
- `is_unicast_link_local_strict`
- `is_documentation`
- `multicast_scope`
- `is_multicast`
- `to_ipv4_mapped`
- `to_ipv4`
Changed the implementation of `is_unspecified` and `is_loopback` to use a `match` instead of `==`.
Part of #76205
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The old code already made the assumption to reinterpret
`Ipv6Addr` as `[u16; 8]`.
Glibc, Linux, FreeBSD, Win32 all makes this assumption.
The main motivation of using union it to better optimize code.
ref:
* https://docs.microsoft.com/en-us/windows/win32/api/in6addr/ns-in6addr-in6_addr
* https://github.com/freebsd/freebsd/blob/1d6e4247415d264485ee94b59fdbc12e0c566fd0/contrib/ntp/lib/isc/include/isc/ipv6.h#L63
* https://github.com/zephyrproject-rtos/zephyr/blob/8b531aa996bba254c03129658490af59597acd78/include/net/net_ip.h#L137
* https://sourceware.org/git/?p=glibc.git;a=blob;f=inet/netinet/in.h;h=f6355c7efe5192b88337b136ef687fe9a5ed648c;hb=HEAD#l216
Co-authored-by: Josh Stone <cuviper@gmail.com>
Co-authored-by: Peter Atashian <retep998@gmail.com>
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Rename intra_doc_link_resolution_failure
It should be plural to follow the conventions in https://github.com/rust-lang/rfcs/blob/master/text/0344-conventions-galore.md#lints
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necessary
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This commit is a proof-of-concept for switching the standard library's
backtrace symbolication mechanism on most platforms from libbacktrace to
gimli. The standard library's support for `RUST_BACKTRACE=1` requires
in-process parsing of object files and DWARF debug information to
interpret it and print the filename/line number of stack frames as part
of a backtrace.
Historically this support in the standard library has come from a
library called "libbacktrace". The libbacktrace library seems to have
been extracted from gcc at some point and is written in C. We've had a
lot of issues with libbacktrace over time, unfortunately, though. The
library does not appear to be actively maintained since we've had
patches sit for months-to-years without comments. We have discovered a
good number of soundness issues with the library itself, both when
parsing valid DWARF as well as invalid DWARF. This is enough of an issue
that the libs team has previously decided that we cannot feed untrusted
inputs to libbacktrace. This also doesn't take into account the
portability of libbacktrace which has been difficult to manage and
maintain over time. While possible there are lots of exceptions and it's
the main C dependency of the standard library right now.
For years it's been the desire to switch over to a Rust-based solution
for symbolicating backtraces. It's been assumed that we'll be using the
Gimli family of crates for this purpose, which are targeted at safely
and efficiently parsing DWARF debug information. I've been working
recently to shore up the Gimli support in the `backtrace` crate. As of a
few weeks ago the `backtrace` crate, by default, uses Gimli when loaded
from crates.io. This transition has gone well enough that I figured it
was time to start talking seriously about this change to the standard
library.
This commit is a preview of what's probably the best way to integrate
the `backtrace` crate into the standard library with the Gimli feature
turned on. While today it's used as a crates.io dependency, this commit
switches the `backtrace` crate to a submodule of this repository which
will need to be updated manually. This is not done lightly, but is
thought to be the best solution. The primary reason for this is that the
`backtrace` crate needs to do some pretty nontrivial filesystem
interactions to locate debug information. Working without `std::fs` is
not an option, and while it might be possible to do some sort of
trait-based solution when prototyped it was found to be too unergonomic.
Using a submodule allows the `backtrace` crate to build as a submodule
of the `std` crate itself, enabling it to use `std::fs` and such.
Otherwise this adds new dependencies to the standard library. This step
requires extra attention because this means that these crates are now
going to be included with all Rust programs by default. It's important
to note, however, that we're already shipping libbacktrace with all Rust
programs by default and it has a bunch of C code implementing all of
this internally anyway, so we're basically already switching
already-shipping functionality to Rust from C.
* `object` - this crate is used to parse object file headers and
contents. Very low-level support is used from this crate and almost
all of it is disabled. Largely we're just using struct definitions as
well as convenience methods internally to read bytes and such.
* `addr2line` - this is the main meat of the implementation for
symbolication. This crate depends on `gimli` for DWARF parsing and
then provides interfaces needed by the `backtrace` crate to turn an
address into a filename / line number. This crate is actually pretty
small (fits in a single file almost!) and mirrors most of what
`dwarf.c` does for libbacktrace.
* `miniz_oxide` - the libbacktrace crate transparently handles
compressed debug information which is compressed with zlib. This crate
is used to decompress compressed debug sections.
* `gimli` - not actually used directly, but a dependency of `addr2line`.
* `adler32`- not used directly either, but a dependency of
`miniz_oxide`.
The goal of this change is to improve the safety of backtrace
symbolication in the standard library, especially in the face of
possibly malformed DWARF debug information. Even to this day we're still
seeing segfaults in libbacktrace which could possibly become security
vulnerabilities. This change should almost entirely eliminate this
possibility whilc also paving the way forward to adding more features
like split debug information.
Some references for those interested are:
* Original addition of libbacktrace - #12602
* OOM with libbacktrace - #24231
* Backtrace failure due to use of uninitialized value - #28447
* Possibility to feed untrusted data to libbacktrace - #21889
* Soundness fix for libbacktrace - #33729
* Crash in libbacktrace - #39468
* Support for macOS, never merged - ianlancetaylor/libbacktrace#2
* Performance issues with libbacktrace - #29293, #37477
* Update procedure is quite complicated due to how many patches we
need to carry - #50955
* Libbacktrace doesn't work on MinGW with dynamic libs - #71060
* Segfault in libbacktrace on macOS - #71397
Switching to Rust will not make us immune to all of these issues. The
crashes are expected to go away, but correctness and performance may
still have bugs arise. The gimli and `backtrace` crates, however, are
actively maintained unlike libbacktrace, so this should enable us to at
least efficiently apply fixes as situations come up.
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