Make io::Error use 64 bits on targets with 64 bit pointers.
I've wanted this for a long time, but didn't see a good way to do it without having extra allocation. When looking at it yesterday, it was more clear what to do for some reason.
This approach avoids any additional allocations, and reduces the size by half (8 bytes, down from 16). AFAICT it doesn't come additional runtime cost, and the compiler seems to do a better job with code using it.
Additionally, this `io::Error` has a niche (still), so `io::Result<()>` is *also* 64 bits (8 bytes, down from 16), and `io::Result<usize>` (used for lots of io trait functions) is 2x64 bits (16 bytes, down from 24 — this means on x86_64 it can use the nice rax/rdx 2-reg struct return). More generally, it shaves a whole 64 bit integer register off of the size of basically any `io::Result<()>`.
(For clarity: Improving `io::Result` (rather than io::Error) was most of the motivation for this)
On 32 bit (or other non-64bit) targets we still use something equivalent the old repr — I don't think think there's improving it, since one of the fields it stores is a `i32`, so we can't get below that, and it's already about as close as we can get to it.
---
### Isn't Pointer Tagging Dodgy?
The details of the layout, and why its implemented the way it is, are explained in the header comment of library/std/src/io/error/repr_bitpacked.rs. There's probably more details than there need to be, but I didn't trim it down that much, since there's a lot of stuff I did deliberately, that might have not seemed that way.
There's actually only one variant holding a pointer which gets tagged. This one is the (holder for the) user-provided error.
I believe the scheme used to tag it is not UB, and that it preserves pointer provenance (even though often pointer tagging does not) because the tagging operation is just `core::ptr::add`, and untagging is `core::ptr::sub`. The result of both operations lands inside the original allocation, so it would follow the safety contract of `core::ptr::{add,sub}`.
The other pointer this had to encode is not tagged — or rather, the tagged repr is equivalent to untagged (it's tagged with 0b00, and has >=4b alignment, so we can reuse the bottom bits). And the other variants we encode are just integers, which (which can be untagged using bitwise operations without worry — they're integers).
CC `@RalfJung` for the stuff in repr_bitpacked.rs, as my comments are informed by a lot of the UCG work, but it's possible I missed something or got it wrong (even if the implementation is okay, there are parts of the header comment that says things like "We can't do $x" which could be false).
---
### Why So Many Changes?
The repr change was mostly internal, but changed one widely used API: I had to switch how `io::Error::new_const` works.
This required switching `io::Error::new_const` to take the full message data (including the kind) as a `&'static`, rather than just the string. This would have been really tedious, but I made a macro that made it much simpler, but it was a wide change since `io::Error::new_const` is used everywhere.
This included changing files for a lot of targets I don't have easy access to (SGX? Haiku? Windows? Who has heard of these things), so I expect there to be spottiness in CI initially, unless luck is on my side.
Anyway this large only tangentially-related change is all in the first commit (although that commit also pulls the previous repr out into its own file), whereas the packing stuff is all in commit 2.
---
P.S. I haven't looked at all of this since writing it, and will do a pass over it again later, sorry for any obvious typos or w/e. I also definitely repeat myself in comments and such.
(It probably could use more tests too. I did some basic testing, and made it so we `debug_assert!` in cases the decode isn't what we encoded, but I don't know the degree which I can assume libstd's testing of IO would exercise this. That is: it wouldn't be surprising to me if libstds IO testing were minimal, especially around error cases, although I have no idea).
The dark and ayu themes have a menu-like highlight on sidebar items. The
light theme used to, but it was accidentally lost in the sidebar
unification. The change brings back the hover effect in the light theme.
It also makes the hover effect apply consistently to all links in the
sidebar, including headings.
It also simplifies the "In _path_" heading so it's one big link. The
breadcrumbs are still readily available at the top of the page.
Factor out several utils, add `path_def_id`
changelog: none
This is generally an effort to reduce the total number of utils. `path_def_id` is added which I believe is more "cross-cutting" and also complements `path_to_local`. Best reviewed one commit at a time.
Added:
* `path_def_id`
* `path_res`
Removed:
* `is_qpath_def_path`
* `match_any_diagnostic_items`
* `expr_path_res`
* `single_segment_path`
* `differing_macro_contexts`
* `is_ty_param_lang_item`
* `is_ty_param_diagnostic_item`
* `get_qpath_generics`
Renamed:
* `path_to_res` to `def_path_res`
* `get_qpath_generic_tys` to `qpath_generic_tys`
CC `@Jarcho` since this relates to some of your work and you may have input.
bootstrap: prefer using '--config' over 'RUST_BOOTSTRAP_CONFIG'
Signed-off-by: Muhammad Falak R Wani <falakreyaz@gmail.com>
Closes: #93725
Rleated: #92260
Rerun bootstrap's build script when RUSTC changes
Previously, rustbuild would give strange errors if you tried to reuse the same build directory under two names:
```
$ mkdir tmp && cd tmp
$ ../x.py check
Building rustbuild
Finished dev [unoptimized] target(s) in 35.27s
Checking stage0 std artifacts (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
^C
$ cd ..
$ mv tmp/build build
$ ./x.py check
Building rustbuild
Compiling bootstrap v0.0.0 (/home/jnelson/rust-lang/rust/src/bootstrap)
Finished dev [unoptimized] target(s) in 11.18s
failed to execute command: "/home/jnelson/rust-lang/rust/tmp/build/x86_64-unknown-linux-gnu/stage0/bin/rustc" "--target" "x86_64-unknown-linux-gnu" "--print" "target-libdir"
error: No such file or directory (os error 2)
```
This fixes the error. Reusing the same build directory is useful if you want to test path-related things in
bootstrap itself, without having to recompile it each time.
For good measure, this also reruns the build script when PATH changes.
Use shallow clones for submodules managed by rustbuild, not just bootstrap.py
I missed this in https://github.com/rust-lang/rust/pull/89757; it made
`x.py test src/bootstrap` very slow.
Update tracking issue for `const_fn_trait_bound`
It previously pointed to #57563, the conglomerate issue for `const fn` (presumably under the feature gate `const_fn`). This tracking issue doesn't mention anything about `const_fn_trait_bound`(the only occurrence of "trait bound" is for the now-removed `?const Trait` syntax), which can be confusing to people who want to find out more about trait bounds on `const fn`s. This pull request changes the tracking issue to one meant specifically for `const_fn_trait_bound`, #93706, which can help collect information on this feature's stabilization and point users towards `const_trait_impl` if they're looking for const-in-const-contexts trait bounds.
Fixes#93679.
`````@rustbot````` modify labels +A-const-fn +F-const_trait_impl
Linkify sidebar headings for sibling items
Also adjust CSS so this doesn't produce excess padding/margin.
Note: I tried and failed to write a test with browser-UI-test. First I tried to `assert-property: (".block.mod h3 a", {"href": "index.html#macros"})`. But the `href` that gets read out is the fully-quallified URL, starting with `file:///`. That URL will differ depending on what path the test is run from, so that doesn't work.
Next I tried clicking on the appropriate sidebar link, and verifying that the appropriate heading on the next page is highlighted with the right background color. However, that also didn't work: according to browser-UI-test, the targeted heading was plain white. However, running with no-headless, I could see that it actually was yellow. I suspect this is a bug in the older version of Chromium used with browser-UI-test's bundled puppeteer, since it doesn't reproduce on latest Chrome.
Fixes#92957
Demo: https://rustdoc.crud.net/jsha/linkify-sidebar-headings/std/string/trait.ToString.html
r? ``@GuillaumeGomez``
Impl {Add,Sub,Mul,Div,Rem,BitXor,BitOr,BitAnd}Assign<$t> for Wrapping<$t> for rust 1.60.0
Tracking issue #93204
This is about adding basic integer operations to the `Wrapping` type:
```rust
let mut value = Wrapping(2u8);
value += 3u8;
value -= 1u8;
value *= 2u8;
value /= 2u8;
value %= 2u8;
value ^= 255u8;
value |= 123u8;
value &= 2u8;
```
Because this adds stable impls on a stable type, it runs into the following issue if an `#[unstable(...)]` attribute is used:
```
an `#[unstable]` annotation here has no effect
note: see issue #55436 <https://github.com/rust-lang/rust/issues/55436> for more information
```
This means - if I understood this correctly - the new impls have to be stabilized instantly.
Which in turn means, this PR has to kick of an FCP on the tracking issue as well?
This impl is analog to 1c0dc1810d778bb6fea16aac02cafc5aa2e84b11 #92356 for the `Saturating` type ``@dtolnay`` ``@Mark-Simulacrum``
Suggest 1-tuple parentheses on exprs without existing parens
A follow-on from #86116, split out from #90677.
This alters the suggestion to add a trailing comma to create a 1-tuple - previously we would only apply this if the relevant expression was parenthesised. We now make the suggestion regardless of parentheses, which reduces the fragility of the check (w.r.t formatting).
e.g.
```rust
let a: Option<(i32,)> = Some(3);
```
gets the below suggestion:
```rust
let a: Option<(i32,)> = Some((3,));
// ^ ^^
```
This change also improves the suggestion in other ways, such as by only making the suggestion if the types would match after the suggestion is applied and making the suggestion a multipart suggestion.
Make the pre-commit script pre-push instead
This should make it substantially less annoying, and hopefully more
people will find it useful. In particular, it will no longer run tidy
each time you run `git commit --amend` or rebase a branch.
This also warns if you have the old script in pre-commit; see the HACK
comment for details.
r? ````@Mark-Simulacrum```` cc ````@caass````
