The `Box<T: Default>` impl currently calls `T::default()` before allocating
the `Box`.
Most `Default` impls are trivial, which should in theory allow
LLVM to construct `T: Default` directly in the `Box` allocation when calling
`<Box<T>>::default()`.
However, the allocation may fail, which necessitates calling `T's` destructor if it has one.
If the destructor is non-trivial, then LLVM has a hard time proving that it's
sound to elide, which makes it construct `T` on the stack first, and then copy it into the allocation.
Create an uninit `Box` first, and then write `T::default` into it, so that LLVM now only needs to prove
that the `T::default` can't panic, which should be trivial for most `Default` impls.
fix/update teach_note from 'escaping mutable ref/ptr' const-check
The old note was quite confusing since it talked about statics, but the message is also shown for consts. So let's reword to something that is true for both of them.
LLVM 20 split out what used to be called b16b16 and correspond to aarch64
FEAT_SVE_B16B16 into sve-b16b16 and sme-b16b16.
Add sme-b16b16 as an explicit feature and update the codegen accordingly.
Reserve guarded string literals (RFC 3593)
Implementation for RFC 3593, including:
- lexer / parser changes
- diagnostics
- migration lint
- tests
We reserve `#"`, `##"`, `###"`, `####`, and any other string of four or more repeated `#`. This avoids infinite lookahead in the lexer, though we still use infinite lookahead in the parser to provide better forward compatibility diagnostics.
This PR does not implement any special lexing of the string internals:
- strings preceded by one or more `#` are denied
- regardless of the number of trailing `#`
- string contents are lexed as if it was just a bare `"string"`
Tracking issue: #123735
RFC: rust-lang/rfcs#3593
Ignore broken-pipe-no-ice on apple (specifically macOS) for now
This test fails for me locally (initially reported by Zalathar) because apparently on macOS it doesn't say "internal compiler error" but it does report the std I/O panic, and it doesn't exit with a code of 101 but instead terminates with a wait signal of SIGPIPE.
Ignore this test on apple for now, until we try to actually address the underlying issue.
See https://github.com/rust-lang/rust/pull/131155 and https://github.com/rust-lang/rust/issues/131436 for more context.
Dont ICE when encountering post-mono layout cycle error
It's possible to encounter post-mono layout cycle errors in `fn_abi_of_instance`. Don't ICE in those cases.
This was originally discovered in an async fn, but that's not the only way to encounter such an error (which the other test I added should demonstrate).
Error messsages suck, but this fix is purely about suppressing the ICE.
Fixes#131409
Prevent building cargo from invalidating build cache of other tools due to conditionally applied `-Zon-broken-pipe=kill` via tracked `RUSTFLAGS`
This PR fixes#130980 where building cargo invalidated the tool build caches of other tools (such as rustdoc) because `-Zon-broken-pipe=kill` was conditionally passed via `RUSTFLAGS` for other tools *except* for cargo. The differing `RUSTFLAGS` triggered tool build cache invalidation as `RUSTFLAGS` is a tracked env var -- any changes in `RUSTFLAGS` requires a rebuild.
`-Zon-broken-pipe=kill` is load-bearing for rustc and rustdoc to not ICE on broken pipes due to usages of raw std `println!` that panics without the flag being set, which manifests in ICEs.
I can't say I like the changes here, but it is what it is...
See detailed discussions and history of `-Zon-broken-pipe=kill` usage in https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Internal.20lint.20for.20raw.20.60print!.60.20and.20.60println!.60.3F/near/474593815.
## Approach
This PR fixes the tool build cache invalidation by informing the `rustc` binary shim when to apply `-Zon-broken-pipe=kill` (i.e. when the rustc binary shim is not used to build cargo). This information is not communicated by `RUSTFLAGS`, which is an env var tracked by cargo, and instead uses an untracked env var `UNTRACKED_BROKEN_PIPE_FLAG` so we won't trigger tool build cache invalidation. We preserve bootstrap's behavior of not setting that flag for cargo by conditionally omitting setting `UNTRACKED_BROKEN_PIPE_FLAG` when building cargo.
Notably, the `-Zon-broken-pipe=kill` instance in 1e5719bdc4/src/bootstrap/src/core/build_steps/compile.rs (L1058) is not modified because that is used to build rustc only and not cargo itself.
Thanks to `@cuviper` for the idea!
## Testing
### Integration testing
This PR introduces a run-make test for rustc and rustdoc that checks that when they do not ICE/panic when they encounter a broken pipe of the stdout stream.
I checked this test will catch the broken pipe ICE regression for rustc on Linux (at least) by commenting out 1e5719bdc4/src/bootstrap/src/core/build_steps/compile.rs (L1058), and the test failed because rustc ICE'd.
### Manual testing
I have manually tried:
1. `./x clean && `./x test build --stage 1` -> `rustc +stage1 --print=sysroot | false`: no ICE.
2. `./x clean` -> `./x test run-make` twice: no stage 1 cargo rebuilds.
3. `./x clean` -> `./x build rustdoc` -> `rustdoc +stage1 --version | false`: no panics.
4. `./x test src/tools/cargo`: tests pass, notably `build::close_output` and `cargo_command::closed_output_ok` do not fail which would fail if cargo was built with `-Zon-broken-pipe=kill`.
## Related discussions
Thanks to everyone who helped!
- https://rust-lang.zulipchat.com/#narrow/stream/246057-t-cargo/topic/Applying.20.60-Zon-broken-pipe.3Dkill.60.20flags.20in.20bootstrap.3F
- https://rust-lang.zulipchat.com/#narrow/stream/326414-t-infra.2Fbootstrap/topic/Modifying.20run-make.20tests.20unnecessarily.20rebuild.20stage.201.20.2E.2E.2E
- https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Internal.20lint.20for.20raw.20.60print!.60.20and.20.60println!.60.3F
Fixes https://github.com/rust-lang/rust/issues/130980
Closes https://github.com/rust-lang/rust/issues/131059
---
try-job: aarch64-apple
try-job: x86_64-msvc
try-job: x86_64-mingw
[Coverage][MCDC] Adapt mcdc to llvm 19
Related issue: #126672
Also finish task 4 at #124144
[llvm #82448](https://github.com/llvm/llvm-project/pull/82448) has introduced some break changes into mcdc, causing incompatibility between llvm 18 and 19. This draft adapts to that change and gives up supporting for llvm-18.
Fix utf8-bom test
The BOM was accidentally removed in https://github.com/rust-lang/rust/pull/57108
I had to move the run-pass line down, because compiletest doesn't seem to know about BOMs, so it does not parse the header if it is the first line.
Add tests for some old fixed issues
Closes#30867Closes#30472Closes#28994Closes#26719 (and migrates the relevant test to the new run-make)
Closes#23600
cc `@jieyouxu` for the run-make-support changes
try-job: x86_64-msvc
Add missing module flags for `-Zfunction-return=thunk-extern`
This fixes a bug in the `-Zfunction-return=thunk-extern` flag. The flag needs to be passed onto LLVM to ensure that functions such as `asan.module_ctor` and `asan.module_dtor` that are created internally in LLVM have the mitigation applied to them.
This was originally discovered [in the Linux kernel](https://lore.kernel.org/all/CANiq72myZL4_poCMuNFevtpYYc0V0embjSuKb7y=C+m3vVA_8g@mail.gmail.com/).
Original flag PR: #116892
PR for similar issue: #129373
Tracking issue: #116853
cc ``@ojeda``
r? ``@wesleywiser``
Add precondition checks to ptr::offset, ptr::add, ptr::sub
All of `offset`, `add`, and `sub` (currently) have the trivial preconditions that the offset in bytes must be <= isize::MAX, and the computation of the new address must not wrap. This adds precondition checks for these, and like in slice indexing, we use intrinsics directly to implement unsafe APIs that have explicit checks, because we get a clearer error message that mentions the misused API not an implementation detail.
Experimentation indicates these checks have 1-2% compile time overhead, due primarily to adding the checks for `add`.
A crater run (https://github.com/rust-lang/rust/pull/130251#issuecomment-2395824565) indicates some people currently have buggy calls to `ptr::offset` that apply a negative offset to a null pointer, but the crater run does not hit the `ptr::add` or `ptr::sub` checks, which seems like an argument for cfg'ing out those checks on account of their overhead.
Don't allow the `#[pointee]` attribute where it doesn't belong
Error if the `#[pointee]` attribute is applied to anything but generic type parameters.
Closes#128485
Related to #123430
