libunwind_panic: adjust miri panic hack
We adjust the Miri hack in libpanic_unwind such that even with `cfg(miri)`, we build a version of libpanic_unwind that actually works.
This is needed to resolve https://github.com/integer32llc/rust-playground/issues/548.
r? @oli-obk @alexcrichton
Remove unneeded prelude imports in libcore tests
These three lines are from c82da7a54b dating back to 2015.
They cause problems when applying rustfmt to the codebase, because reordering wildcard imports can trigger new unused import warnings.
As a minimized example, the following program compiles successfully:
```rust
#![deny(unused_imports)]
use std::fmt::Debug;
use std::marker::Send;
pub mod repro {
use std::prelude::v1::*;
use super::*;
pub type D = dyn Debug;
pub type S = dyn Send;
}
pub type S = dyn Send;
```
but putting it through rustfmt produces a program that fails to compile:
```rust
#![deny(unused_imports)]
use std::fmt::Debug;
use std::marker::Send;
pub mod repro {
use super::*;
use std::prelude::v1::*;
pub type D = dyn Debug;
pub type S = dyn Send;
}
pub type S = dyn Send;
```
The error is:
```console
error: unused import: `std::prelude::v1::*`
--> src/main.rs:8:9
|
8 | use std::prelude::v1::*;
| ^^^^^^^^^^^^^^^^^^^
```
Make python-generated source files compatible with rustfmt
This PR adjusts the generators for src/libcore/num/dec2flt/table.rs, src/libcore/unicode/printable.rs, and src/libcore/unicode/tables.rs to make it so running `rustfmt` on the generated files no longer needs to apply any changes.
This involves tweaking the python scripts where reasonable to better match rustfmt's style, and adding `#[rustfmt::skip]` to big constant tables that there's no point having rustfmt rewrap.
r? @Dylan-DPC
Atomic as_mut_ptr
I encountered the following pattern a few times: In Rust we use some atomic type like `AtomicI32`, and an FFI interface exposes this as `*mut i32` (or some similar `libc` type).
It was not obvious to me if a just transmuting a pointer to the atomic was acceptable, or if this should use a cast that goes through an `UnsafeCell`. See https://github.com/rust-lang/rust/issues/66136#issuecomment-557802477
Transmuting the pointer directly:
```rust
let atomic = AtomicI32::new(1);
let ptr = &atomic as *const AtomicI32 as *mut i32;
unsafe {
ffi(ptr);
}
```
A dance with `UnsafeCell`:
```rust
let atomic = AtomicI32::new(1);
unsafe {
let ptr = (&*(&atomic as *const AtomicI32 as *const UnsafeCell<i32>)).get();
ffi(ptr);
}
```
Maybe in the end both ways could be valid. But why not expose a direct method to get a pointer from the standard library?
An `as_mut_ptr` method on atomics can be safe, because only the use of the resulting pointer is where things can get unsafe. I documented its use for FFI, and "Doing non-atomic reads and writes on the resulting integer can be a data race."
The standard library could make use this method in a few places in the WASM module.
cc @RalfJung as you answered my original question.
These three lines are from c82da7a54b in
2015.
They cause problems when applying rustfmt to the codebase, because
reordering wildcard imports can trigger new unused import warnings.
As a minimized example, the following program compiles successfully:
#![deny(unused_imports)]
use std::fmt::Debug;
use std::marker::Send;
pub mod repro {
use std::prelude::v1::*;
use super::*;
pub type D = dyn Debug;
pub type S = dyn Send;
}
pub type S = dyn Send;
but putting it through rustfmt produces a program that fails to compile:
#![deny(unused_imports)]
use std::fmt::Debug;
use std::marker::Send;
pub mod repro {
use super::*;
use std::prelude::v1::*;
pub type D = dyn Debug;
pub type S = dyn Send;
}
pub type S = dyn Send;
The error is:
error: unused import: `std::prelude::v1::*`
--> src/main.rs:8:9
|
8 | use std::prelude::v1::*;
| ^^^^^^^^^^^^^^^^^^^
Clarify `{f32,f64}::EPSILON` docs
The doc for `EPSILON` says:
> This is the difference between `1.0` and the next **largest** representable number.
Which is a bit unclear.
[Wikipedia](https://en.wikipedia.org/wiki/Machine_epsilon) says
> Machine epsilon is defined as the difference between 1 and the next **larger** floating point number
So this PR update the docs to match the Wikipedia version.
The original PR also has this in a [comment](https://github.com/rust-lang/rust/pull/50919#discussion_r192600209).
Panic machinery comments and tweaks
This is mostly more comments, but I also renamed some things:
* `BoxMeUp::box_me_up` is not terribly descriptive, and since this is a "take"-style method (the argument is `&mut self` but the return type is fully owned, even though you can't tell from the type) I chose a name involving "take".
* `continue_panic_fmt` was very confusing as it was entirely unclear what was being continued -- for some time I thought "continue" might be the same as "resume" for a panic, but that's something entirely different. So I renamed this to `begin_panic_handler`, matching the `begin_panic*` theme of the other entry points.
r? @Dylan-DPC @SimonSapin
Implement Debug for MaybeUninit
Precedent: `UnsafeCell` implements `Debug` even though it can't actually display the value. I noticed this omission while writing the following:
```
#[derive(Debug)]
pub struct SliceInitializer<'a, T> {
marker: PhantomData<&'a mut T>,
uninit: &'a mut [MaybeUninit<T>],
written: usize,
}
```
...which currently unergonomically fails to compile.
`UnsafeCell` does require `T: Debug`. Because of things like the above I think it'd be better to leave that requirement off. In fact, I'd also suggest removing that requirement for `UnsafeCell` too, which again I noticed in some low-level real world code.
Fixes small typo in array docs r? @steveklabnik
Fixes a small typo in the array documentation.
Also, wasn't sure which [message](https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#pull-requests) to put this in, and will definitely update the commit message if it is supposed to be the PR description but for "safety" - r? @steveklabnik
This commit applies rustfmt with default settings to files in
src/libcore *that are not involved in any currently open PR* to minimize
merge conflicts. The list of files involved in open PRs was determined
by querying GitHub's GraphQL API with this script:
https://gist.github.com/dtolnay/aa9c34993dc051a4f344d1b10e4487e8
With the list of files from the script in `outstanding_files`, the
relevant commands were:
$ find src/libcore -name '*.rs' | xargs rustfmt --edition=2018
$ rg libcore outstanding_files | xargs git checkout --
Repeating this process several months apart should get us coverage of
most of the rest of libcore.
Clarify Step Documentation
While the redesign is in progress (#62886), clarify the purpose of replace_zero and replace_one.
First, "returning itself" is technically impossible due to the function signature of &mut self -> Self. A clone or copy operation must be used. So this is now explicitly stated in the documentation.
Second, the added docs give some guidance about the actual contract around implementation of replace_zero and replace one. Specifically, the only usage is to create a range with no more steps, by setting start to replace_one and end to replace_zero. So the only property that is actually used is `replace_one > replace_zero`. See https://github.com/rust-lang/rust/issues/42168#issuecomment-489554232
The new documentation does not say that is the *only* contract, and so it should not be considered an api change. It just highlights the most important detail for implementors.
The redesign doesn't seem to be landing any time soon, so this is a stopgap measure to reduce confusion in the meantime.
add fn type_name_of_val
This function is often useful during testing and mirrors `align_of_val` and `size_of_val`.
# Example
Showing the default type of integers.
```rust
let x = 7;
println!("per default, integers have the type: {}", std::any::type_name_of_val(&x));
```
To my knowledge this can currently not be done without defining a function similar to `type_name_of_val`.
