Add some performance guidance to std::fs and std::io docs
Adds more documentation about performance to various "read" functions in `fs` and `io`, and to `BufReader`/`BufWriter`, with the goal of helping developers choose the best option for a given task.
Re-write the documentation index
The docs team has decided that we're framing resources in three ways:
"learning Rust," "using Rust," "mastering Rust." This is a more useful
split than "beginner/intermediate/advanced." As we add more resources
in the future, we expect "using Rust" to grow. "the bookshelf" as a
concept is great, but isn't really organized along these lines. As such,
this reorganizes the docs along these lines.
Better document the implementors of Clone and Copy
There are two parts to this change. The first part is a change to the compiler and to the standard library (specifically, libcore) to allow implementations of `Clone` and `Copy` to be written for a subset of builtin types. By adding these implementations to libcore, they now show up in the documentation. This is a [breaking-change] for users of `#![no_core]`, because they will now have to supply their own copy of the implementations of `Clone` and `Copy` that were added in libcore.
The second part is purely a documentation change to document the other implementors of `Clone` and `Copy` that cannot be described in Rust code (yet) and are thus provided by the compiler.
Fixes#25893
the goal is to build, in a single Cargo invocation, several no-std crates that we want to put in the
rust-std component of no-std targets. The nostd crate builds these crates:
- core
- compiler-builtin (with the "c" and "mem" features enabled)
- alloc
- std_unicode
Add tests to rustbuild
In order to run tests, we cfg out various parts of rustbuild. Generally
speaking, these are filesystem and process-spawning operations. Then, rustbuild
is run "as normal" and the various steps that where run are retrieved from the
cache and checked against the expected results.
Note that this means that the current implementation primarily tests "what" we
build, but doesn't actually test that what we build *will* build. In other
words, it doesn't do any form of dependency verification for any crate. This is
possible to implement, but is considered future work.
This implementation strives to cfg out as little code as possible; it also does
not currently test anywhere near all of rustbuild. The current tests are also
not checked for "correctness," rather, they simply represent what we do as of
this commit, which may be wrong.
Test cases are drawn from the old implementation of rustbuild, though the
expected results may vary.
r? @alexcrichton
avoid IdxSets containing garbage above the universe length
This makes sure that all bits in each IdxSet between the universe length
and the end of the word are all zero instead of being in an indeterminate state.
This fixes a crash with RUST_LOG=rustc_mir, and is probably a good idea
anyway.
r? @nikomatsakis - I think you are responsible for this code area now?
Introduce Vec::resize_with method (see #41758)
In #41758, the libs team decided they preferred `Vec::resize_with` over `Vec::resize_default()`. Here is an implementation to get this moving forward.
I don't know what the removal process for `Vec::resize_default()` should be, so I've left it in place for now. Would be happy to follow up with its removal.
Add #[must_use] to a few standard library methods
Chosen to start a precedent of using it on ones that are potentially-expensive and where using it for side effects is particularly discouraged.
Discuss :)
```rust
warning: unused return value of `std::iter::Iterator::collect` which must be used: if you really need to exhaust the iterator, consider `.for_each(drop)` instead
--> $DIR/fn_must_use_stdlib.rs:19:5
|
LL | "1 2 3".split_whitespace().collect::<Vec<_>>();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
warning: unused return value of `std::borrow::ToOwned::to_owned` which must be used: cloning is often expensive and is not expected to have side effects
--> $DIR/fn_must_use_stdlib.rs:21:5
|
LL | "hello".to_owned();
| ^^^^^^^^^^^^^^^^^^^
warning: unused return value of `std::clone::Clone::clone` which must be used: cloning is often expensive and is not expected to have side effects
--> $DIR/fn_must_use_stdlib.rs:23:5
|
LL | String::from("world").clone();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```
cc https://github.com/rust-lang/rust/issues/48926
rustc_driver: get rid of the extra thread
**Do not rollup**
We can alter the stack size afterwards on Unix.
Having a separate thread causes poor debugging experience when interrupting with signals. I have to get the backtrace of the all thread, as the main thread is waiting to join doing nothing else. This patch allows me to just run `bt` to get the desired backtrace.
Reject huge alignments on macos with system allocator only
ef8804ba27 addressed #30170 by rejecting
huge alignments at the allocator API level, transforming a specific
platform bug/limitation into an enforced API limitation on all
platforms.
This change essentially reverts that commit, and instead makes alloc()
itself return AllocErr::Unsupported when receiving huge alignments.
This was discussed in https://github.com/rust-lang/rust/issues/32838#issuecomment-368348408
and following.
Update sccache to its master branch
Ideally I'd like to soon enable sccache for rustbuild itself and some of the
stage0 tools, but for that to work we'll need some better Rust support than the
pretty old version we were previously using!
