Make Arc cloning mechanics clearer in module docs
Add some more wording to module documentation regarding how
`Arc::clone()` works, as some users have assumed cloning Arc's
to work via dereferencing to inner value as follows:
use std::sync::Arc;
let myarc = Arc::new(1);
let myarcref = myarc.clone();
assert!(1 == myarcref);
Instead of the actual mechanic of referencing the existing
Arc value:
use std::sync::Arg;
let myarc = Arc::new(1);
let myarcref = myarc.clone();
assert!(myarcref == &myarc); // not sure if assert could assert this in the real world
Reoptimize VecDeque::append
~Unfortunately, I don't know if these changes fix the unsoundness mentioned in #53529, so it is stil a WIP.
This is also completely untested.
The VecDeque code contains other unsound code: one example : [reading unitialized memory](https://play.rust-lang.org/?gist=6ff47551769af61fd8adc45c44010887&version=nightly&mode=release&edition=2015) (detected by MIRI), so I think this code will need a bigger refactor to make it clearer and safer.~
Note: this is based on #53571.
r? @SimonSapin
Cc: #53529#52553 @YorickPeterse @jonas-schievink @Pazzaz @shepmaster.
Add some more wording to module documentation regarding how
`Arc::clone()` works, as some users have assumed cloning Arc's
to work via dereferencing to inner value as follows:
use std::sync::Arc;
let myarc = Arc::new(1);
let myarcref = myarc.clone();
assert!(1 == myarcref);
Instead of the actual mechanic of referencing the existing
Arc value:
use std::sync::Arg;
let myarc = Arc::new(1);
let myarcref = myarc.clone();
assert!(myarcref == &myarc); // not sure if assert could assert this
in the real world
move the Pin API into its own module for centralized documentation
This implements the change proposed by @withoutboats in #49150, as suggested by @RalfJung in the review of #53104,
along with the documentation that was originally in it, that was deemed more appropriate in module-level documentation.
r? @RalfJung
docs: minor stylistic changes to str/string docs
std::string::String.repeat(): slightly rephrase to be more in-line with other descriptions.
add ticks around a few keywords in other descriptions.
Rollup of 17 pull requests
Successful merges:
- #53030 (Updated RELEASES.md for 1.29.0)
- #53104 (expand the documentation on the `Unpin` trait)
- #53213 (Stabilize IP associated constants)
- #53296 (When closure with no arguments was expected, suggest wrapping)
- #53329 (Replace usages of ptr::offset with ptr::{add,sub}.)
- #53363 (add individual docs to `core::num::NonZero*`)
- #53370 (Stabilize macro_vis_matcher)
- #53393 (Mark libserialize functions as inline)
- #53405 (restore the page title after escaping out of a search)
- #53452 (Change target triple used to check for lldb in build-manifest)
- #53462 (Document Box::into_raw returns non-null ptr)
- #53465 (Remove LinkMeta struct)
- #53492 (update lld submodule to include RISCV patch)
- #53496 (Fix typos found by codespell.)
- #53521 (syntax: Optimize some literal parsing)
- #53540 (Moved issue-53157.rs into src/test/ui/consts/const-eval/)
- #53551 (Avoid some Place clones.)
Failed merges:
r? @ghost
Change `Rc::inc_{weak,strong}` to better hint optimization to LLVM
As discussed in #13018, `Rc::inc_strong` and `Rc::inc_weak` are changed to allow compositions of `clone` and `drop` to be better optimized. Almost entirely as in [this comment](https://github.com/rust-lang/rust/issues/13018#issuecomment-408642184), except that `abort` on zero is added so that a `drop(t.clone())` does not produce a zero check followed by conditional deallocation.
This is different from #21418 in that it doesn't rely on `assume`, avoiding the prohibitive compilation slowdown.
[Before and after IR](https://gist.github.com/hermord/266e55451b7fe0bb8caa6e35d17c86e1).
Non-naive implementation of `VecDeque.append`
Replaces the old, simple implementation with a more manual (and **unsafe** 😱) one. I've added 1 more test and verified that it covers all 6 code paths in the function.
This new implementation was about 60% faster than the old naive one when I tried benchmarking it.
