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splat-fn-ptr-ptr-tuple.rs: add let to avoid UB - #161403

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TimNN:splat-ub
Aug 21, 2026
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splat-fn-ptr-ptr-tuple.rs: add let to avoid UB#161403
rust-bors[bot] merged 1 commit into
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TimNN:splat-ub

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@TimNN

@TimNN TimNN commented Aug 20, 2026 •
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Fixes #161323.

Miri previously reported UB when running this test, and LLVM 24 treated it as UB.

r? @teor2345

I'm not sure what exactly is getting tested here, but based on your comment on the issue I assume that moving these to a let binding is fine.

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Aug 20, 2026
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Error: Failed to set assignee to teor2345: invalid assignee

Note: Only org members with at least the repository "read" role, users with write permissions, or people who have commented on the PR may be assigned.

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@TimNN

TimNN commented Aug 20, 2026

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@rustbot reroll

@teor2345

teor2345 commented Aug 20, 2026

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This test makes sure that rustc doesn't panic when compiling splats within function pointers, see #158603. It also tests the codegen correctly tuples the caller's arguments.

rust/tests/ui/splat/splat-fn-ptr-ptr-tuple.rs

Line 1 in 8925ea3

//! Test using `#[rustc_splat]` on tuple arguments of pointers to pointers to simple functions.

I have to comment before anyone can assign me, that should hopefully be fixed soon. But I can't approve for merge, so you'll need someone else to review it anyway.

@rustbot label +F-splat

@rustbot rustbot added the F-splat `#![feature(splat)]` https://github.com/rust-lang/rust/issues/153629 label Aug 20, 2026
teor2345
teor2345 approved these changes Aug 20, 2026
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Thanks!

This adds a simple extra binding, to stop the casted function pointer being dropped before use.

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fee1-dead commented Aug 21, 2026

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@bors r+ rollup

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📌 Commit 9da8a55 has been approved by fee1-dead

It is now in the queue for this repository.

@rust-bors rust-bors Bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 21, 2026
JonathanBrouwer added a commit to JonathanBrouwer/rust that referenced this pull request Aug 21, 2026
@JonathanBrouwer
Rollup merge of rust-lang#161403 - TimNN:splat-ub, r=fee1-dead
211c304 
splat-fn-ptr-ptr-tuple.rs: add `let` to avoid UB

Fixes rust-lang#161323.

Miri previously reported UB when running this test, and LLVM 24 treated it as UB.

r? @teor2345

I'm not sure what _exactly_ is getting tested here, but based on your comment on the issue I assume that moving these to a `let` binding is fine.
@JonathanBrouwer JonathanBrouwer mentioned this pull request Aug 21, 2026
Closed
JonathanBrouwer added a commit to JonathanBrouwer/rust that referenced this pull request Aug 21, 2026
@JonathanBrouwer
Rollup merge of rust-lang#161403 - TimNN:splat-ub, r=fee1-dead
48d73b2 
splat-fn-ptr-ptr-tuple.rs: add `let` to avoid UB

Fixes rust-lang#161323.

Miri previously reported UB when running this test, and LLVM 24 treated it as UB.

r? @teor2345

I'm not sure what _exactly_ is getting tested here, but based on your comment on the issue I assume that moving these to a `let` binding is fine.
@JonathanBrouwer JonathanBrouwer mentioned this pull request Aug 21, 2026
Closed
JonathanBrouwer added a commit to JonathanBrouwer/rust that referenced this pull request Aug 21, 2026
@JonathanBrouwer
Rollup merge of rust-lang#161403 - TimNN:splat-ub, r=fee1-dead
69b2d97 
splat-fn-ptr-ptr-tuple.rs: add `let` to avoid UB

Fixes rust-lang#161323.

Miri previously reported UB when running this test, and LLVM 24 treated it as UB.

r? @teor2345

I'm not sure what _exactly_ is getting tested here, but based on your comment on the issue I assume that moving these to a `let` binding is fine.
@JonathanBrouwer JonathanBrouwer mentioned this pull request Aug 21, 2026
Closed
rust-bors Bot pushed a commit that referenced this pull request Aug 21, 2026
@bors
Auto merge of #161455 - JonathanBrouwer:rollup-hQbbeP7, r=JonathanBro…
aeca481 
…uwer

Rollup of 16 pull requests

Successful merges:

 - #161259 (move some attribute related structs out of rustc_attr_ir)
 - #160853 (delegation: simplify matches on `FnKind`, minor refactorings)
 - #159899 ( `GenericArgs::types` triage + possible fixes)
 - #160459 (Use attribute parser for `deprecated` attribute checking)
 - #160813 (Optimize linked list iterator performance)
 - #161271 (doc: document safety requirements for core WTF-8)
 - #161317 (LLVM 24: configure float-abi via module flag)
 - #161320 (Only suggest `RUST_MIN_STACK` if maybe stack overflow)
 - #161369 (Add regression test for confusing lifetime error message issue)
 - #161393 (Configure LLM policy URL for triagebot)
 - #161403 (splat-fn-ptr-ptr-tuple.rs: add `let` to avoid UB)
 - #161409 (Add back `tests/rustdoc-gui/notable-trait.goml` test)
 - #161410 (Fix rustdoc remapping `documentation` scope documentation)
 - #161415 (Update expect messages in path docs to better follow guidelines)
 - #161438 (Change triagebot backport to ping T-libs-fcp)
 - #161442 (Add regression test for dead code on type alias used in impl self type)

Failed merges:

 - #160509 (Remove `RegionExt`; move methods to `Region` in `rustc_type_ir`)
@jhpratt jhpratt mentioned this pull request Aug 21, 2026
Merged
rust-bors Bot pushed a commit that referenced this pull request Aug 21, 2026
@bors
Auto merge of #161458 - jhpratt:rollup-q1wVzyt, r=jhpratt
a872286 
Rollup of 20 pull requests

Successful merges:

 - #161259 (move some attribute related structs out of rustc_attr_ir)
 - #160853 (delegation: simplify matches on `FnKind`, minor refactorings)
 - #161161 (proc_macro: add support for 16-bit targets)
 - #159899 ( `GenericArgs::types` triage + possible fixes)
 - #160459 (Use attribute parser for `deprecated` attribute checking)
 - #160536 (Inline `String::into_raw_parts` and reuse `from_utf16` optimization)
 - #160563 (Make `BorrowedCursor<'a, T>` covariant in `'a` and drop an indirection)
 - #160595 (Clarify `str::split_at` docs)
 - #160813 (Optimize linked list iterator performance)
 - #161271 (doc: document safety requirements for core WTF-8)
 - #161317 (LLVM 24: configure float-abi via module flag)
 - #161320 (Only suggest `RUST_MIN_STACK` if maybe stack overflow)
 - #161369 (Add regression test for confusing lifetime error message issue)
 - #161393 (Configure LLM policy URL for triagebot)
 - #161403 (splat-fn-ptr-ptr-tuple.rs: add `let` to avoid UB)
 - #161409 (Add back `tests/rustdoc-gui/notable-trait.goml` test)
 - #161410 (Fix rustdoc remapping `documentation` scope documentation)
 - #161415 (Update expect messages in path docs to better follow guidelines)
 - #161438 (Change triagebot backport to ping T-libs-fcp)
 - #161442 (Add regression test for dead code on type alias used in impl self type)

Failed merges:

 - #160509 (Remove `RegionExt`; move methods to `Region` in `rustc_type_ir`)
@rust-bors
rust-bors Bot merged commit c258e82 into rust-lang:main Aug 21, 2026
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@rustbot rustbot added this to the 1.100.0 milestone Aug 21, 2026
rust-bors Bot pushed a commit that referenced this pull request Aug 21, 2026
@bors
Unrolled build for #161403 in rollup 161458
feda66f 
Rollup merge of #161403 - TimNN:splat-ub, r=fee1-dead

splat-fn-ptr-ptr-tuple.rs: add `let` to avoid UB

Fixes #161323.

Miri previously reported UB when running this test, and LLVM 24 treated it as UB.

r? @teor2345

I'm not sure what _exactly_ is getting tested here, but based on your comment on the issue I assume that moving these to a `let` binding is fine.
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F-splat `#![feature(splat)]` https://github.com/rust-lang/rust/issues/153629 S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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splat-fn-ptr-ptr-tuple.rs fails under miri and crashes under LLVM 24

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