Add attributes for #[global_allocator] functions #146766

nikic · 2025-09-19T13:06:00Z

Emit #[rustc_allocator] etc. attributes on the functions generated by the #[global_allocator] macro, which will emit LLVM attributes like "alloc-family". If the module with the global allocator participates in LTO, this ensures that the attributes typically emitted on the allocator declarations are not lost if the definition is imported.

There is a similar issue when the allocator shim is used, but I've opted not to fix that case in this PR, because doing that cleanly is somewhat gnarly.

Related to #145995.

rustbot · 2025-09-19T13:06:05Z

r? @nnethercote

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nnethercote · 2025-09-20T05:14:01Z

tests/codegen-llvm/global-allocator-attributes.rs

+            // CHECK-LABEL: ; __rustc::__rust_alloc
+            // CHECK-NEXT: ; Function Attrs: {{.*}}allockind("alloc,uninitialized,aligned") allocsize(0){{.*}}
+            // CHECK-NEXT: define noalias{{.*}} ptr @{{.*}}__rust_alloc(i64 {{.*}}%size, i64 allocalign{{.*}} %align)
+            panic!()


How the the addition of the attribute change the behaviour here? I.e. what part of the checked stuff would have been missing?

Basically all the attributes with alloc in the name (allockind, allocsize, allocalign, etc.) would be missing.

nnethercote · 2025-09-20T05:15:16Z

@bors r+ rollup

bors · 2025-09-20T05:15:19Z

📌 Commit 06b0076 has been approved by nnethercote

It is now in the queue for this repository.

…cote Add attributes for #[global_allocator] functions Emit `#[rustc_allocator]` etc. attributes on the functions generated by the `#[global_allocator]` macro, which will emit LLVM attributes like `"alloc-family"`. If the module with the global allocator participates in LTO, this ensures that the attributes typically emitted on the allocator declarations are not lost if the definition is imported. There is a similar issue when the allocator shim is used, but I've opted not to fix that case in this PR, because doing that cleanly is somewhat gnarly. Related to rust-lang#145995.

Rollup of 6 pull requests Successful merges: - #144592 (generate list of all variants with `target_spec_enum`) - #146762 (Fix and provide instructions for running test suite on Apple simulators) - #146766 (Add attributes for #[global_allocator] functions) - #146770 (fixes for numerous clippy warnings) - #146774 (Allow running `x <cmd> <path>` from a different directory) - #146800 (Fix unsupported `std::sys::thread` after move) r? `@ghost` `@rustbot` modify labels: rollup

matthiaskrgr · 2025-09-20T15:54:40Z

@bors r-

#146807 (comment)

nikic · 2025-09-22T10:21:19Z

@bors try jobs=armhf-gnu

Add attributes for #[global_allocator] functions try-job: armhf-gnu

rust-bors · 2025-09-22T12:01:07Z

☀️ Try build successful (CI)
Build commit: 73fa854 (73fa8543bc6dd139d6a6727e1f434b0dda89adb1, parent: 9f32ccf35fb877270bc44a86a126440f04d676d0)

nikic · 2025-09-22T12:28:05Z

@bors r=nnethercote rollup=iffy

bors · 2025-09-22T12:28:08Z

📌 Commit b6456cd has been approved by nnethercote

It is now in the queue for this repository.

RalfJung · 2025-09-22T16:24:31Z

This fixes a regression introduced by #144086 which is on the beta branch (and hasn't been reverted there I think?), so nominating for beta backport.

mati865 · 2025-09-22T17:22:43Z

An alternative would be to revert the original #144086
It's an optimisation, not a bugfix, so this might be a reasonable solution.

Add attributes for #[global_allocator] functions Emit `#[rustc_allocator]` etc. attributes on the functions generated by the `#[global_allocator]` macro, which will emit LLVM attributes like `"alloc-family"`. If the module with the global allocator participates in LTO, this ensures that the attributes typically emitted on the allocator declarations are not lost if the definition is imported. There is a similar issue when the allocator shim is used, but I've opted not to fix that case in this PR, because doing that cleanly is somewhat gnarly. Related to #145995.

bors · 2025-09-22T20:57:01Z

⌛ Testing commit b6456cd with merge 1932ce3...

Emit `#[rustc_allocator]` etc. attributes on the functions generated by the `#[global_allocator]` macro, which will emit LLVM attributes like `"alloc-family"`. If the module with the global allocator participates in LTO, this ensures that the attributes typically emitted on the allocator declarations are not lost if the definition is imported.

nikic · 2025-09-23T08:21:51Z

@bors try jobs=test-various

Add attributes for #[global_allocator] functions try-job: test-various

rust-bors · 2025-09-23T10:09:11Z

☀️ Try build successful (CI)
Build commit: b7eea9f (b7eea9faff5906b26488eb7bf5ac397d9379749e, parent: f6092f224d2b1774b31033f12d0bee626943b02f)

clubby789 · 2025-09-23T10:20:27Z

@bors r=nnethercote rollup=iffy

bors · 2025-09-23T10:20:29Z

📌 Commit bc7986e has been approved by nnethercote

It is now in the queue for this repository.

…cote Add attributes for #[global_allocator] functions Emit `#[rustc_allocator]` etc. attributes on the functions generated by the `#[global_allocator]` macro, which will emit LLVM attributes like `"alloc-family"`. If the module with the global allocator participates in LTO, this ensures that the attributes typically emitted on the allocator declarations are not lost if the definition is imported. There is a similar issue when the allocator shim is used, but I've opted not to fix that case in this PR, because doing that cleanly is somewhat gnarly. Related to rust-lang#145995.

Rollup of 14 pull requests Successful merges: - #145067 (RawVecInner: add missing `unsafe` to unsafe fns) - #145277 (Do not materialise X in [X; 0] when X is unsizing a const) - #145973 (Add `std` support for `armv7a-vex-v5`) - #146667 (Add an attribute to check the number of lanes in a SIMD vector after monomorphization) - #146735 (unstably constify float mul_add methods) - #146737 (f16_f128: enable some more tests in Miri) - #146766 (Add attributes for #[global_allocator] functions) - #146905 (llvm: update remarks support on LLVM 22) - #146982 (Remove erroneous normalization step in `tests/run-make/linker-warning`) - #147005 (Small string formatting cleanup) - #147007 (Explicitly note `&[SocketAddr]` impl of `ToSocketAddrs`) - #147008 (bootstrap.py: Respect build.jobs while building bootstrap tool) - #147013 (rustdoc: Fix documentation for `--doctest-build-arg`) - #147015 (Use `LLVMDisposeTargetMachine`) r? `@ghost` `@rustbot` modify labels: rollup

apiraino · 2025-09-25T14:06:13Z

Beta backport declined as per compiler team on Zulip. As suggested by Nikita, a revert in beta si preferred.

@rustbot label -beta-nominated

RalfJung · 2025-09-25T14:31:53Z

@nikic will you handle doing the revert?

nikic · 2025-09-25T14:38:47Z

@RalfJung Sure, I put up a PR at #147030. Not sure what the process for beta reverts is, do I have to beta-nominate that PR?

Rollup merge of #146766 - nikic:global-alloc-attr, r=nnethercote Add attributes for #[global_allocator] functions Emit `#[rustc_allocator]` etc. attributes on the functions generated by the `#[global_allocator]` macro, which will emit LLVM attributes like `"alloc-family"`. If the module with the global allocator participates in LTO, this ensures that the attributes typically emitted on the allocator declarations are not lost if the definition is imported. There is a similar issue when the allocator shim is used, but I've opted not to fix that case in this PR, because doing that cleanly is somewhat gnarly. Related to #145995.

Rollup of 14 pull requests Successful merges: - rust-lang/rust#145067 (RawVecInner: add missing `unsafe` to unsafe fns) - rust-lang/rust#145277 (Do not materialise X in [X; 0] when X is unsizing a const) - rust-lang/rust#145973 (Add `std` support for `armv7a-vex-v5`) - rust-lang/rust#146667 (Add an attribute to check the number of lanes in a SIMD vector after monomorphization) - rust-lang/rust#146735 (unstably constify float mul_add methods) - rust-lang/rust#146737 (f16_f128: enable some more tests in Miri) - rust-lang/rust#146766 (Add attributes for #[global_allocator] functions) - rust-lang/rust#146905 (llvm: update remarks support on LLVM 22) - rust-lang/rust#146982 (Remove erroneous normalization step in `tests/run-make/linker-warning`) - rust-lang/rust#147005 (Small string formatting cleanup) - rust-lang/rust#147007 (Explicitly note `&[SocketAddr]` impl of `ToSocketAddrs`) - rust-lang/rust#147008 (bootstrap.py: Respect build.jobs while building bootstrap tool) - rust-lang/rust#147013 (rustdoc: Fix documentation for `--doctest-build-arg`) - rust-lang/rust#147015 (Use `LLVMDisposeTargetMachine`) r? `@ghost` `@rustbot` modify labels: rollup

Revert "Auto merge of #144086 - clubby789:alloc-zeroed, r=nikic" This reverts commit 040a98a, reversing changes made to e8a792d. This reverts #144086 on beta due to #145995. On master the issue will be fixed by #146766.

Emit allocator attributes for allocator shim This emits the same attributes we place on allocator declarations on the definitions in the allocator shim as well. This complements rust-lang#146766, which added the attribute for `#[global_allocator]` definitions. Emitting the attributes on the definitions ensures that they cannot be lost of the allocator shim participates in LTO. See rust-lang#145995 for context, though that one was about `#[global_allocator]`. I'm not sure whether this can occur with the allocator shim as well or not, but better safe than sorry. I'm not sure whether there is any good way to test this, as the allocator shim is not part of `--emit=llvm-ir`. I've verified this locally by inspecting the bitcode produced by `-C save-temps`. r? `@bjorn3`

Emit allocator attributes for allocator shim This emits the same attributes we place on allocator declarations on the definitions in the allocator shim as well. This complements rust-lang#146766, which added the attribute for `#[global_allocator]` definitions. Emitting the attributes on the definitions ensures that they cannot be lost of the allocator shim participates in LTO. See rust-lang#145995 for context, though that one was about `#[global_allocator]`. I'm not sure whether this can occur with the allocator shim as well or not, but better safe than sorry. I'm not sure whether there is any good way to test this, as the allocator shim is not part of `--emit=llvm-ir`. I've verified this locally by inspecting the bitcode produced by `-C save-temps`. r? ``@bjorn3``

Rollup merge of #147150 - nikic:alloc-shim-attributes, r=bjorn3 Emit allocator attributes for allocator shim This emits the same attributes we place on allocator declarations on the definitions in the allocator shim as well. This complements #146766, which added the attribute for `#[global_allocator]` definitions. Emitting the attributes on the definitions ensures that they cannot be lost of the allocator shim participates in LTO. See #145995 for context, though that one was about `#[global_allocator]`. I'm not sure whether this can occur with the allocator shim as well or not, but better safe than sorry. I'm not sure whether there is any good way to test this, as the allocator shim is not part of `--emit=llvm-ir`. I've verified this locally by inspecting the bitcode produced by `-C save-temps`. r? ``@bjorn3``

rustbot assigned nnethercote Sep 19, 2025

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Rollup of 6 pull requests #146807

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nikic force-pushed the global-alloc-attr branch from 06b0076 to b6456cd Compare September 22, 2025 10:20

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Auto merge of #146766 - nikic:global-alloc-attr, r=<try>

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Add attributes for #[global_allocator] functions try-job: armhf-gnu

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Auto merge of #146766 - nikic:global-alloc-attr, r=<try>

b7eea9f

Add attributes for #[global_allocator] functions try-job: test-various

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Rollup of 14 pull requests #146966

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Rollup of 14 pull requests #147019

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nikic mentioned this pull request Sep 25, 2025

Revert "Auto merge of #144086 - clubby789:alloc-zeroed, r=nikic" #147030

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bors merged commit 46e25aa into rust-lang:master Sep 25, 2025
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nikic mentioned this pull request Sep 25, 2025

alloc-variant-zeroed causing issues with LTO #145995

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nikic mentioned this pull request Sep 29, 2025

Emit allocator attributes for allocator shim #147150

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Add attributes for #[global_allocator] functions #146766

Add attributes for #[global_allocator] functions #146766

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