Link MSVC default lib in core
## The Problem
On Windows MSVC, Rust invokes the linker directly. This means only the objects and libraries Rust explicitly passes to the linker are used. In short, this is equivalent to passing `-nodefaultlibs`, `-nostartfiles`, etc for gnu compilers.
To compensate for this [the libc crate links to the necessary libraries](a0f5b4b213/src/windows/mod.rs (L258-L261)). The libc crate is then linked from std, thus when you use std you get the defaults back.or integrate with C/C++.
However, this has a few problems:
- For `no_std`, users are left to manually pass the default lib to the linker
- Whereas `std` has the opposite problem, using [`/nodefaultlib`](https://learn.microsoft.com/en-us/cpp/build/reference/nodefaultlib-ignore-libraries?view=msvc-170) doesn't work as expected because Rust treats them as normal libs. This is a particular problem when you want to use e.g. the debug CRT libraries in their place or integrate with C/C++..
## The solution
This PR fixes this in two ways:
- moves linking the default lib into `core`
- passes the lib to the linker using [`/defaultlib`](https://learn.microsoft.com/en-us/cpp/build/reference/defaultlib-specify-default-library?view=msvc-170). This allows users to override it in the normal way (i.e. with [`/nodefaultlib`](https://learn.microsoft.com/en-us/cpp/build/reference/nodefaultlib-ignore-libraries?view=msvc-170)).
This is more or less equivalent to what the MSVC C compiler does. You can see what this looks like in my second commit, which I'll reproduce here for convenience:
```rust
// In library/core
#[cfg(all(windows, target_env = "msvc"))]
#[link(
name = "/defaultlib:msvcrt",
modifiers = "+verbatim",
cfg(not(target_feature = "crt-static"))
)]
#[link(name = "/defaultlib:libcmt", modifiers = "+verbatim", cfg(target_feature = "crt-static"))]
extern "C" {}
```
## Alternatives
- Add the above to `unwind` and `std` but not `core`
- The status quo
- Some other kind of compiler magic maybe
This bares some discussion so I've t-libs nominated it.
Doc: replace x with y for hexa-decimal fmt
I found it a bit unintuitive to know which is variable and which is the format string in `format!("{x:x}")`, so I switched it to `y`.
Get rid of `USIZE_MARKER` in formatting infrastructure
An alternative to #123780.
The `USIZE_MARKER` function used to differentiate between placeholder and count arguments is never called anyway, so we can just replace the function-pointer-comparison hack with an `enum` and an `unreachable_unchecked`, hopefully without causing a regression.
CC `@RalfJung`
Update stdarch submodule
`asm_experimental_arch` is required in `core` as we're now using unstable inline assembly when building Arm64EC.
Brings in the fix for <https://github.com/rust-lang/stdarch/issues/1555> (cc `@tslnc04).`
r? `@Amanieu`
Add a `Debug` impl and some basic functions to `f16` and `f128`
`compiler_builtins` uses some convenience functions like `is_nan` and `is_sign_positive`. Add these, as well as a temporary implementation for `Debug` that prints the bit representation.
Rollup of 8 pull requests
Successful merges:
- #122882 (Avoid a panic in `set_output_capture` in the default panic handler)
- #123523 (Account for trait/impl difference when suggesting changing argument from ref to mut ref)
- #123744 (Silence `unused_imports` for redundant imports)
- #123784 (Replace `document.write` with `document.head.insertAdjacent`)
- #123798 (Avoid invalid socket address in length calculation)
- #123804 (Stop using `HirId` for fn-like parents since closures are not `OwnerNode`s)
- #123806 (Panic on overflow in `BorrowedCursor::advance`)
- #123820 (Add my former address to .mailmap)
r? `@ghost`
`@rustbot` modify labels: rollup
Panic on overflow in `BorrowedCursor::advance`
Passing `usize::MAX` to `advance` clearly isn't correct, but the current assertion fails to detect this when overflow checks are disabled. This isn't unsound, but should probably be fixed regardless.
`compiler_builtins` uses some convenience functions like `is_nan` and
`is_sign_positive`. Add these, as well as a temporary implementation for
`Debug` that prints the bit representation.
This reverts commit 049a917535.
The resolution to <https://github.com/rust-lang/rust/issues/123282> is
that the `f16`/`f128` regression in the beta compiler was fixable
without a revert, so the commit adding `#[cfg(not(bootstrap))]` is no
longer useful (added in
<https://github.com/rust-lang/rust/pull/123390>).
Revert this commit because not having these basic impls bootstrap-gated
simplifies everything else that uses them.
Don't emit divide-by-zero panic paths in `StepBy::len`
I happened to notice today that there's actually two such calls emitted in the assembly: <https://rust.godbolt.org/z/1Wbbd3Ts6>
Since they're impossible, hopefully telling LLVM that will also help optimizations elsewhere.
Implement minimal, internal-only pattern types in the type system
rebase of https://github.com/rust-lang/rust/pull/107606
You can create pattern types with `std::pat::pattern_type!(ty is pat)`. The feature is incomplete and will panic on you if you use any pattern other than integral range patterns. The only way to create or deconstruct a pattern type is via `transmute`.
This PR's implementation differs from the MCP's text. Specifically
> This means you could implement different traits for different pattern types with the same base type. Thus, we just forbid implementing any traits for pattern types.
is violated in this PR. The reason is that we do need impls after all in order to make them usable as fields. constants of type `std::time::Nanoseconds` struct are used in patterns, so the type must be structural-eq, which it only can be if you derive several traits on it. It doesn't need to be structural-eq recursively, so we can just manually implement the relevant traits on the pattern type and use the pattern type as a private field.
Waiting on:
* [x] move all unrelated commits into their own PRs.
* [x] fix niche computation (see 2db07f94f44f078daffe5823680d07d4fded883f)
* [x] add lots more tests
* [x] T-types MCP https://github.com/rust-lang/types-team/issues/126 to finish
* [x] some commit cleanup
* [x] full self-review
* [x] remove 61bd325da19a918cc3e02bbbdce97281a389c648, it's not necessary anymore I think.
* [ ] ~~make sure we never accidentally leak pattern types to user code (add stability checks or feature gate checks and appopriate tests)~~ we don't even do this for the new float primitives
* [x] get approval that [the scope expansion to trait impls](https://rust-lang.zulipchat.com/#narrow/stream/326866-t-types.2Fnominated/topic/Pattern.20types.20types-team.23126/near/427670099) is ok
r? `@BoxyUwU`
Documentation fix
Changed "It must not be an identical residual when interconversion is involved" to "The residual is not mandated to be identical when interconversion is involved." as the previous parenthetical appears to state that the residual is not permitted to be identical when interconversion is involved. However the intention of the original wording was to convey that the residual is not required to be identical when interconversion is involved, which makes more sense contextually.
Use unchecked_sub in str indexing
https://github.com/rust-lang/rust/pull/108763 applied this logic to indexing for slices, but of course `str` has its own separate impl.
Found this by skimming over the codegen for https://github.com/oxidecomputer/hubris/; their dist builds enable overflow checks so the lack of `unchecked_sub` was producing an impossible-to-hit overflow check and also inhibiting some inlining.
r? scottmcm
Stabilize const Atomic*::into_inner
Partial stabilization for https://github.com/rust-lang/rust/issues/78729, for which the FCP has already completed.
The other `into_inner` functions in that tracking issue (`UnsafeCell`, `Cell`, `RefCell`) are blocked on https://github.com/rust-lang/rust/issues/73255 for now.
```console
error[E0493]: destructor of `UnsafeCell<T>` cannot be evaluated at compile-time
--> library/core/src/cell.rs:2076:29
|
2076 | pub const fn into_inner(self) -> T {
| ^^^^ the destructor for this type cannot be evaluated in constant functions
2077 | self.value
2078 | }
| - value is dropped here
```
I happened to notice today that there's actually two such calls emitted in the assembly: <https://rust.godbolt.org/z/1Wbbd3Ts6>
Since they're impossible, hopefully telling LLVM that will also help optimizations elsewhere.
