Fix 72 byte memory leak in worker destruction #23053
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WalkthroughReorders and consolidates VirtualMachine shutdown: removes immediate per-thread destructor calls in globalExit, adds explicit teardown of the forever timer and GC controller in deinit, and makes transpiler and auto_killer deinitialization conditional on running on the main thread. Changes
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✨ Finishing touches🧪 Generate unit tests
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📒 Files selected for processing (1)
src/bun.js/VirtualMachine.zig(1 hunks)
🧰 Additional context used
📓 Path-based instructions (3)
src/**/*.zig
📄 CodeRabbit inference engine (.cursor/rules/building-bun.mdc)
Implement debug logs in Zig using
const log = bun.Output.scoped(.${SCOPE}, false);and invokinglog("...", .{})
Files:
src/bun.js/VirtualMachine.zig
**/*.zig
📄 CodeRabbit inference engine (.cursor/rules/javascriptcore-class.mdc)
**/*.zig: Declare the extern C symbol in Zig and export a Zig-friendly alias for use
Wrap the Bun____toJS extern in a Zig method that takes a JSGlobalObject and returns JSC.JSValue
**/*.zig: Format Zig files with zig-format (bun run zig-format)
In Zig, manage memory carefully with allocators and use defer for cleanup
Files:
src/bun.js/VirtualMachine.zig
src/bun.js/**/*.zig
📄 CodeRabbit inference engine (.cursor/rules/zig-javascriptcore-classes.mdc)
src/bun.js/**/*.zig: In Zig binding structs, expose generated bindings via pub const js = JSC.Codegen.JS and re-export toJS/fromJS/fromJSDirect
Constructors and prototype methods should return bun.JSError!JSC.JSValue to integrate Zig error handling with JS exceptions
Use parameter name globalObject (not ctx) and accept (*JSC.JSGlobalObject, *JSC.CallFrame) in binding methods/constructors
Implement getters as get(this, globalObject) returning JSC.JSValue and matching the .classes.ts interface
Provide deinit() for resource cleanup and finalize() that calls deinit(); use bun.destroy(this) or appropriate destroy pattern
Access JS call data via CallFrame (argument(i), argumentCount(), thisValue()) and throw errors with globalObject.throw(...)
For properties marked cache: true, use the generated Zig accessors (NameSetCached/GetCached) to work with GC-owned values
In finalize() for objects holding JS references, release them using .deref() before destroy
Files:
src/bun.js/VirtualMachine.zig
🧠 Learnings (4)
📓 Common learnings
Learnt from: CR
PR: oven-sh/bun#0
File: .cursor/rules/zig-javascriptcore-classes.mdc:0-0
Timestamp: 2025-08-30T00:13:36.815Z
Learning: Applies to src/bun.js/**/*.zig : Provide deinit() for resource cleanup and finalize() that calls deinit(); use bun.destroy(this) or appropriate destroy pattern
Learnt from: CR
PR: oven-sh/bun#0
File: .cursor/rules/zig-javascriptcore-classes.mdc:0-0
Timestamp: 2025-08-30T00:13:36.815Z
Learning: Applies to src/bun.js/**/*.zig : In finalize() for objects holding JS references, release them using .deref() before destroy
Learnt from: CR
PR: oven-sh/bun#0
File: .cursor/rules/registering-bun-modules.mdc:0-0
Timestamp: 2025-08-30T00:11:57.076Z
Learning: Applies to src/**/js_*.zig : Always implement proper cleanup in deinit() and finalize() for JS-exposed types
📚 Learning: 2025-08-30T00:13:36.815Z
Learnt from: CR
PR: oven-sh/bun#0
File: .cursor/rules/zig-javascriptcore-classes.mdc:0-0
Timestamp: 2025-08-30T00:13:36.815Z
Learning: Applies to src/bun.js/**/*.zig : Provide deinit() for resource cleanup and finalize() that calls deinit(); use bun.destroy(this) or appropriate destroy pattern
Applied to files:
src/bun.js/VirtualMachine.zig
📚 Learning: 2025-08-30T00:13:36.815Z
Learnt from: CR
PR: oven-sh/bun#0
File: .cursor/rules/zig-javascriptcore-classes.mdc:0-0
Timestamp: 2025-08-30T00:13:36.815Z
Learning: Applies to src/bun.js/**/*.zig : In finalize() for objects holding JS references, release them using .deref() before destroy
Applied to files:
src/bun.js/VirtualMachine.zig
📚 Learning: 2025-08-30T00:11:57.076Z
Learnt from: CR
PR: oven-sh/bun#0
File: .cursor/rules/registering-bun-modules.mdc:0-0
Timestamp: 2025-08-30T00:11:57.076Z
Learning: Applies to src/**/js_*.zig : Always implement proper cleanup in deinit() and finalize() for JS-exposed types
Applied to files:
src/bun.js/VirtualMachine.zig
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Actionable comments posted: 1
📜 Review details
Configuration used: CodeRabbit UI
Review profile: CHILL
Plan: Pro
Disabled knowledge base sources:
- Linear integration is disabled by default for public repositories
You can enable these sources in your CodeRabbit configuration.
📒 Files selected for processing (1)
src/bun.js/VirtualMachine.zig(2 hunks)
🧰 Additional context used
📓 Path-based instructions (3)
src/**/*.zig
📄 CodeRabbit inference engine (.cursor/rules/building-bun.mdc)
Implement debug logs in Zig using
const log = bun.Output.scoped(.${SCOPE}, false);and invokinglog("...", .{})
Files:
src/bun.js/VirtualMachine.zig
**/*.zig
📄 CodeRabbit inference engine (.cursor/rules/javascriptcore-class.mdc)
**/*.zig: Declare the extern C symbol in Zig and export a Zig-friendly alias for use
Wrap the Bun____toJS extern in a Zig method that takes a JSGlobalObject and returns JSC.JSValue
**/*.zig: Format Zig files with zig-format (bun run zig-format)
In Zig, manage memory carefully with allocators and use defer for cleanup
Files:
src/bun.js/VirtualMachine.zig
src/bun.js/**/*.zig
📄 CodeRabbit inference engine (.cursor/rules/zig-javascriptcore-classes.mdc)
src/bun.js/**/*.zig: In Zig binding structs, expose generated bindings via pub const js = JSC.Codegen.JS and re-export toJS/fromJS/fromJSDirect
Constructors and prototype methods should return bun.JSError!JSC.JSValue to integrate Zig error handling with JS exceptions
Use parameter name globalObject (not ctx) and accept (*JSC.JSGlobalObject, *JSC.CallFrame) in binding methods/constructors
Implement getters as get(this, globalObject) returning JSC.JSValue and matching the .classes.ts interface
Provide deinit() for resource cleanup and finalize() that calls deinit(); use bun.destroy(this) or appropriate destroy pattern
Access JS call data via CallFrame (argument(i), argumentCount(), thisValue()) and throw errors with globalObject.throw(...)
For properties marked cache: true, use the generated Zig accessors (NameSetCached/GetCached) to work with GC-owned values
In finalize() for objects holding JS references, release them using .deref() before destroy
Files:
src/bun.js/VirtualMachine.zig
🧠 Learnings (4)
📚 Learning: 2025-08-30T00:13:36.815Z
Learnt from: CR
PR: oven-sh/bun#0
File: .cursor/rules/zig-javascriptcore-classes.mdc:0-0
Timestamp: 2025-08-30T00:13:36.815Z
Learning: Applies to src/bun.js/**/*.zig : Provide deinit() for resource cleanup and finalize() that calls deinit(); use bun.destroy(this) or appropriate destroy pattern
Applied to files:
src/bun.js/VirtualMachine.zig
📚 Learning: 2025-08-30T00:11:57.076Z
Learnt from: CR
PR: oven-sh/bun#0
File: .cursor/rules/registering-bun-modules.mdc:0-0
Timestamp: 2025-08-30T00:11:57.076Z
Learning: Applies to src/**/js_*.zig : Always implement proper cleanup in deinit() and finalize() for JS-exposed types
Applied to files:
src/bun.js/VirtualMachine.zig
📚 Learning: 2025-08-30T00:13:36.815Z
Learnt from: CR
PR: oven-sh/bun#0
File: .cursor/rules/zig-javascriptcore-classes.mdc:0-0
Timestamp: 2025-08-30T00:13:36.815Z
Learning: Applies to src/bun.js/**/*.zig : In finalize() for objects holding JS references, release them using .deref() before destroy
Applied to files:
src/bun.js/VirtualMachine.zig
📚 Learning: 2025-08-30T00:11:00.890Z
Learnt from: CR
PR: oven-sh/bun#0
File: .cursor/rules/javascriptcore-class.mdc:0-0
Timestamp: 2025-08-30T00:11:00.890Z
Learning: Applies to src/bun.js/bindings/ZigGlobalObject.cpp : Initialize the LazyClassStructure in GlobalObject::finishCreation and visit it in GlobalObject::visitChildrenImpl
Applied to files:
src/bun.js/VirtualMachine.zig
| if (this.is_main_thread) { | ||
| this.transpiler.deinit(); | ||
| this.auto_killer.deinit(); | ||
| } |
There was a problem hiding this comment.
is_main_thread guard never fires
is_main_thread defaults to false on the struct and none of the construction paths (init, initWithModuleGraph, initWorker, etc.) ever flip it to true. With this check in place we now skip both transpiler.deinit() and auto_killer.deinit() for every VM, regressing cleanup and leaking a lot more than the 72 B you’re chasing. Please gate on this.isMainThread() (or ensure the flag is set) so we still tear these resources down.
- if (this.is_main_thread) {
+ if (this.isMainThread()) {
this.transpiler.deinit();
this.auto_killer.deinit();
}📝 Committable suggestion
‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.
| if (this.is_main_thread) { | |
| this.transpiler.deinit(); | |
| this.auto_killer.deinit(); | |
| } | |
| if (this.isMainThread()) { | |
| this.transpiler.deinit(); | |
| this.auto_killer.deinit(); | |
| } |
🤖 Prompt for AI Agents
In src/bun.js/VirtualMachine.zig around lines 1930 to 1933, the current guard
uses the struct field this.is_main_thread which defaults to false and is never
set, so the cleanup for transpiler and auto_killer never runs; change the guard
to call this.isMainThread() (or alternatively ensure all VM constructors set
this.is_main_thread = true for main-thread VMs) so that transpiler.deinit() and
auto_killer.deinit() are invoked when appropriate and resources are torn down.
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