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fix(allocator): StringBuilder use Allocator::alloc_layout#21340

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Apr 12, 2026
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fix(allocator): StringBuilder use Allocator::alloc_layout#21340
graphite-app[bot] merged 1 commit intomainfrom
om/04-12-fix_allocator_stringbuilder_use_allocator_alloc_layout_

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@overlookmotel overlookmotel commented Apr 12, 2026

StringBuilder methods were allocating using allocator.bump().alloc_layout(layout) i.e. allocating directly via Bump. Switch to allocating via Allocator with allocator.alloc_layout(layout). This shortens the code and also correctly counts the allocations in allocator tracker - previously they were being ignored in the allocation counts.

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overlookmotel commented Apr 12, 2026


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codspeed-hq Bot commented Apr 12, 2026

Merging this PR will improve performance by 3.67%

⚡ 1 improved benchmark
✅ 47 untouched benchmarks
⏩ 3 skipped benchmarks1

Performance Changes

Mode Benchmark BASE HEAD Efficiency
Simulation mangler[RadixUIAdoptionSection.jsx_keep_names] 20.3 µs 19.6 µs +3.67%

Comparing om/04-12-fix_allocator_stringbuilder_use_allocator_alloc_layout_ (36f505f) with om/04-12-perf_formatter_use_allocator_alloc_concat_strs_array_instead_of_stringbuilder_from_strs_array_in_ (0ce619f)

Open in CodSpeed

Footnotes

  1. 3 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports.

@overlookmotel overlookmotel self-assigned this Apr 12, 2026
@overlookmotel overlookmotel marked this pull request as ready for review April 12, 2026 14:38
Copilot AI review requested due to automatic review settings April 12, 2026 14:38
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Pull request overview

Updates StringBuilder to allocate via Allocator::alloc_layout (instead of calling into Bump directly) so allocation tracking is correctly recorded by the allocator stats machinery.

Changes:

  • Switch StringBuilder’s internal layout allocations to allocator.alloc_layout(layout) so allocations are counted by the tracker.
  • Update memory-allocation tracking snapshots to reflect the newly counted arena allocations.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File Description
crates/oxc_allocator/src/string_builder.rs Routes StringBuilder allocations through Allocator::alloc_layout to ensure allocation tracking is applied.
tasks/track_memory_allocations/allocs_transformer.snap Snapshot update reflecting adjusted arena allocation counts after tracking fix.
tasks/track_memory_allocations/allocs_parser.snap Snapshot update reflecting adjusted arena allocation counts after tracking fix.

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graphite-app Bot commented Apr 12, 2026

Merge activity

`StringBuilder` methods were allocating using `allocator.bump().alloc_layout(layout)` i.e. allocating directly via `Bump`. Switch to allocating via `Allocator` with `allocator.alloc_layout(layout)`. This shortens the code and also correctly counts the allocations in allocator tracker - previously they were being ignored in the allocation counts.
@graphite-app graphite-app Bot force-pushed the om/04-12-perf_formatter_use_allocator_alloc_concat_strs_array_instead_of_stringbuilder_from_strs_array_in_ branch from 5375723 to 0ce619f Compare April 12, 2026 15:06
@graphite-app graphite-app Bot requested review from Dunqing and leaysgur as code owners April 12, 2026 15:06
@graphite-app graphite-app Bot force-pushed the om/04-12-fix_allocator_stringbuilder_use_allocator_alloc_layout_ branch from c3603c0 to 36f505f Compare April 12, 2026 15:07
Base automatically changed from om/04-12-perf_formatter_use_allocator_alloc_concat_strs_array_instead_of_stringbuilder_from_strs_array_in_ to main April 12, 2026 15:16
@graphite-app graphite-app Bot merged commit 36f505f into main Apr 12, 2026
37 checks passed
@graphite-app graphite-app Bot deleted the om/04-12-fix_allocator_stringbuilder_use_allocator_alloc_layout_ branch April 12, 2026 15:18
camc314 pushed a commit that referenced this pull request Apr 13, 2026
### 💥 BREAKING CHANGES

- 36cdc31 str: [**BREAKING**] Remove identity `FromIn` impl for `Ident`
(#21251) (overlookmotel)
- 382958a span: [**BREAKING**] Remove re-exports of string types from
`oxc_span` crate (#21246) (overlookmotel)
- c4aedfa str: [**BREAKING**] Add `static_ident!` macro (#21245)
(overlookmotel)

### 🚀 Features

- e7e1aea transformer/typescript: Add `optimize_enums` option for
regular enum inlining (#20539) (Dunqing)
- 679f57f transformer/typescript: Implement const enum inlining and
declaration removal (#20508) (Dunqing)
- 6dd061c semantic: Extend `MemberWriteTarget` to cover all property
modification patterns (#21205) (Dunqing)
- f134e24 minifier: Support `property_write_side_effects` option to drop
unused property assignments (#20773) (Dunqing)
- 75663c0 semantic: Add enum member value evaluation for const enum
support (#20602) (Dunqing)
- 3cfe8ed semantic: Add `MemberWriteTarget` flag to `ReferenceFlags`
(#20772) (Dunqing)

### 🐛 Bug Fixes

- af1a586 transformer/class-properties: Use correct property name when
converting parameter properties (#21268) (Amal Jossy)
- b43250a allocator: Move allocation tracking into `Bump` (#21342)
(overlookmotel)
- 36f505f allocator: `StringBuilder` use `Allocator::alloc_layout`
(#21340) (overlookmotel)
- 7a08a6f allocator: Fix allocation counting in
`Allocator::alloc_concat_strs_array` (#21336) (overlookmotel)
- 2338e28 ecmascript: Treat `this` as potentially having side effects
(#21297) (sapphi-red)
- bd8bd39 allocator: Remove unsafe hacks from `from_raw_parts` methods
(#21283) (overlookmotel)
- 8f4c340 allocator: Remove dangerous pointer const to mut cast (#21279)
(overlookmotel)
- aa9259f parser: Add missing error code for optional param diagnostic
(#21258) (camc314)
- 04b3c2f str: Fix unsound casting const pointers to mut pointers
(#21242) (overlookmotel)
- ceadf6c str: Make `Ident::from_raw` an unsafe function (#21241)
(overlookmotel)
- eab13b3 transformer/decorators: Avoid accessor storage name collisions
(#21106) (Dunqing)
- 07e8a30 transformer/react-refresh: Handle parenthesized variable
initializers (#21047) (camc314)

### ⚡ Performance

- c3ca6f6 allocator: `StringBuilder::from_strs_array_in` check for 0
length earlier (#21338) (overlookmotel)
- c2422bb allocator: `Allocator::alloc_concat_strs_array` check for 0
length earlier (#21337) (overlookmotel)
- 04b0fdc allocator: Mark `Allocator::alloc_layout` as
`#[inline(always)]` (#21335) (overlookmotel)
- 17aee9e allocator: Use `offset_from_unsigned` in
`ChunkFooter::as_raw_parts` (#21280) (overlookmotel)
- 61adedd minifier: Fix O(n²) perf on very many var decls (#21062)
(Gunnlaugur Thor Briem)
- addcd02 napi/parser, linter/plugins: Raw transfer deserializer for
`Vec`s use shift instead of multiply where possible (#21142)
(overlookmotel)
- 3068ded napi/parser, linter/plugins: Shift before add when calculating
positions in raw transfer deserializer (#21141) (overlookmotel)
- eb400b8 napi/parser, linter/plugins: Remove `uint32` buffer view
(#21140) (overlookmotel)
- 2675085 napi/parser: Lazy deserialization use only `Int32Array`
(#21139) (overlookmotel)
- 5b35a53 napi/parser: Deserializing tokens use only `int32` array
(#21138) (overlookmotel)
- f163d10 parser: Tokens raw deserialization use `Int32Array` (#21137)
(overlookmotel)
- 7a86613 linter/plugins: Use `Int32Array`s for tokens and comments
buffers (#21136) (overlookmotel)
- 8c51121 napi/parser, linter/plugins: Raw transfer deserialize `Span`
fields as `i32`s (#21135) (overlookmotel)
- bc1bcdd napi/parser, linter/plugins: Inline trivial raw transfer field
deserializers into node object definitions (#21134) (overlookmotel)
- c0278ab napi/parser, linter/plugins: Use `Int32Array` in raw transfer
deserializer (#21132) (overlookmotel)
- 43482c7 linter/plugins: Use `>>` not `>>>` in binary search loops
(#21129) (overlookmotel)

### 📚 Documentation

- f5e1845 allocator: Upgrade headers in doc comments for `Bump` (#21263)
(overlookmotel)
- 2870174 allocator: Upper case `SAFETY` in comments (#21253)
(overlookmotel)
- 01bc269 str: Reformat `Ident` doc comments (#21240) (overlookmotel)
- dd47359 allocator: Add doc comments for panics and errors (#21230)
(overlookmotel)
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