process: let inline caches work on process.env and process.argv - #44356
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…ess.execArgv Each first read of an environment variable changed the structure of process.env. After 128 changes JSC made it a dictionary, and reads were no longer cached. The values are now plain data properties from the start, on one structure. process.argv and process.execArgv called a native getter on every read. They are now lazy data properties, as in Node.js. A write to process.env from the same site could skip the conversion to a string, because the inline cache stored the value directly. Writes are no longer cached.
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Updated 10:56 AM PT - Oct 1st, 2026
❌ @robobun, your commit e6621c3 has 1 failures in
🧪 To try this PR locally: bunx bun-pr 44356That installs a local version of the PR into your bun-44356 --bun |
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Navigate logical layers of code changes, visualize relationships, and explore their blast radius. No actionable comments were generated in the recent review. 🎉 ℹ️ Recent review info⚙️ Run configurationConfiguration used: Repository: oven-sh/bun/.coderabbit.yaml Review profile: ASSERTIVE Plan: Essentials Run ID: 📒 Files selected for processing (2)
Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 2 remain after this review. WalkthroughThe changes update environment-map initialization and worker environment objects. They replace cached ChangesProcess properties
Suggested reviewers: Priority: ➖ Normal Merge Risk: 🟡 Moderate · up to Argument-array construction failures may leave lazy process properties in invalid state. Resolve the exception-handling boundary before merging; its exact engine behavior remains unverified. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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- 🪄 Fix CodeRabbit comments on this PR
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Review comments at @src/jsc/bindings/BunProcess.cpp:
- Line 3175: Update the lazy builders for Bun__Process__createArgv and its
sibling builder to check for a pending exception after construction and return
through the exception-aware path before reifyStaticProperty installs the value;
follow the existing handling in BunProcess.cpp or use an exception-aware
materialization path that preserves the construction error.
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📒 Files selected for processing (9)
bench/snippets/process-env.mjssrc/jsc/bindings/BunProcess.cppsrc/jsc/bindings/BunProcess.hsrc/jsc/bindings/InspectorLifecycleAgent.cppsrc/jsc/bindings/JSEnvironmentVariableMap.cppsrc/jsc/bindings/JSEnvironmentVariableMap.hsrc/jsc/bindings/ZigGlobalObject.cppsrc/runtime/api/BunObject.rstest/js/node/process/process.test.js
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- src/jsc/bindings/BunProcess.h
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@robobun fix |
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All 8 review threads are answered and resolved. The 2 red findings and the CodeRabbit finding do not reproduce on this branch. 1d95a0b (tests only) covers the 2 nits. ba9ff1c fixes the later finding: a first write to a proxy variable, |
…uplicate name, cover Bun.argv - The hot-write tests run 10,000 writes, not 300,000. They turn the concurrent JIT off and lower the FTL threshold, so write() is in the FTL within the first 400 calls. A debug build needed 8.7 s for the old loop and the test timed out there. - The spawn tests for process.env are concurrent. - Two names that are not valid UTF-8 and decode to the same string: the test expects the value of the first one in the environment. - New test: Bun.argv keeps no value when the process.argv getter throws. The next read calls the getter again.
…erty put() stored TZ, NODE_TLS_REJECT_UNAUTHORIZED and the proxy variables with putDirect and no slot. With more than 128 properties on process.env, JSC makes the object a dictionary when such a store adds a property. The JIT flattens a dictionary one time only. After the next such store, a read of a variable that is not set is not cached again: 3,400 to 4,000 ns per read against about 70 ns (debug build, 200 variables). These stores now use the PutById slot that put() has for every other name, so the limit is 512 properties for all of them. The custom setters add their private value the same way, and get the same slot. On POSIX only the BUN_CONFIG_VERBOSE_FETCH setter runs for process.env: put() handles the other two names.
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I re-reviewed the two pushes since my last pass (ba9ff1c, 1d95a0b) and found no new bugs; the proxy-variable putDirect store I flagged earlier now goes through the same PutById slot as every other put() path. Because the change relies on JSC structure-transition and inline-cache semantics (putDirectWithoutTransition, PutById dictionary thresholds, lazy static properties) and leaves a known DFG gap as an it.todo, a human look is still worthwhile.
What was reviewed:
createEnvironmentVariablesMap/ worker env seeding:Bun__getEnvValueAtindexes the same parallelkeys()/values()arrays asBun__getEnvCount, withi < countfrom the caller and a Rust panic (not UB) on overrun; the duplicate-name skip only needs to cover 16-bit decodes, since an 8-bit result implies valid, byte-unique UTF-8.Process::getArgv/getExecArgvcallers:Bun__Process__getArgv/getExecArgvnow carry a ThrowScope, the Rust side usescall_zero_is_throwand?inparse_args.rs, andInspectorLifecycleAgentusesdynamicDowncastafter the exception check.- Removed
m_argv/m_execArgvWriteBarriers have no remaining readers;processObject()is agetInitializedOnMainThreadlazy property, so the dropped null checks cannot be reached with null. - TZ getter no longer caches; the private slot is seeded at creation for a non-empty value, so re-reads only re-copy when native code sets TZ after creation.
Extended reasoning...
The PR rewrites how process.env (POSIX), process.argv and process.execArgv are materialized in src/jsc/bindings so JSC inline caches stay valid: eager data properties added via putDirectWithoutTransition, a fresh PutById slot for every store in put() and the three custom setters, argv/execArgv as PropertyCallback lazy properties, plus a new Rust FFI Bun__getEnvValueAt and six subprocess tests. It touches no auth, crypto, or injection surface; the sensitive part is engine-level structure/IC behavior, which is hard to verify by reading alone. The latest commit addressed the one open nit from my previous review and the earlier findings have tests or CI coverage (test-worker-process-argv.js, the Bun.argv throwing-getter test), and the hunt ran dry with no findings, so nothing blocks; the complexity and the acknowledged DFG PutByStatus gap (it.todo) are why I defer rather than approve.
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The JSC change for the What it does: I built this branch merged with main against the preview build of that PR (
The first and third "Before" values are from a debug build of this branch plus main with the pinned WebKit. The fourth is from release 1.4.3-canary.1. The rest of Two more paths store into Order: oven-sh/WebKit#764 merges first. Then a Bun PR bumps |
Expose Node-compatible descriptors for common process properties so descriptor-preserving overrides work. Keep argv and execArgv lazy while routing native readers through the public property, and preserve live ppid/title behavior behind native data descriptors. Ports relevant argv and metadata changes from oven-sh#44356 and oven-sh#34229; thanks @robobun. Node 24 oracle, 1,094 combined Bun tests, 48 OpenClaw consumer tests, scoped P2 review, and both native CI lanes passed on the guarded head.
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What does this PR do?
Reads of
process.env.X,process.argvandprocess.execArgvnow cost the same as reads of a plain object, in every JIT tier.process.env.XCustomValue. The first read replaced it, which is a structure transition. After 128 transitions JSC makes the object an uncacheable dictionary, and the JIT flattens a dictionary only once.{...process.env}with 63 variables is enough.process.envof aWorker.process.env.TZprocess.env[key] = valuePutByIdcontext).process.argv,process.execArgvCustomAccessor: a native call on each read.ns per read. Release builds of this branch and of its merge base, macOS arm64, 125 variables. "plain" is the same code on
{...process.env}/[...process.argv].process.argvprocess.env.SETprocess.env.NOT_SET, after{...process.env}, a hot read andprocess.env[key] = valueObject.keys(process.env), same statebench/snippets/process-env.mjson Node v25.6.0:process.env.HOME77 ns,process.env.NOT_SET160 ns,process.argv10 ns.Cost
The values are no longer lazy. Median of 41 processes.
Behavior changes
Object.getOwnPropertyDescriptor(process, "argv"),"execArgv"value,writableget,setvalue,writableutil.parseArgs()afterObject.defineProperty(process, "argv", { get })Bun.argvafterObject.defineProperty(process, "argv", { get })Bun.argvkeeps no valueprocess.env.X = 1, many times from one site"1"1, from about the 4th write"1"(one gap, below)undefinedgetModuleGraphafterprocess.argv = 1JSArrayput()gave the caller'sPutPropertySlottoJSObject::put, so the inline cache stored later values directly and skipped the conversion to a string. It now uses its own slot.Gap:
PutByStatus::computeFor(StructureSet)in JSC does not look atOverridesPut. When the DFG has proved the structure ofprocess.env, and the variable also has a JIT-cached read, the DFG still stores the value directly. This needs a change in JSC. Anit.todocovers it.How did you verify your code works?
test/js/node/process/process.test.js. All 7 fail on the merge base and pass on this branch.process.test.js,test-parse-args.mjs,parse_args,process-args,worker_threads,worker,isolation,bun-inspector-protocol: 550 pass, 0 fail (debug + ASAN). Node'stest-process-env*.js,test-process-argv-0.js,test-worker-process-argv.js,test-worker-process-env-shared.js,test-child-process-env.jspass.BUN_JSC_validateExceptionChecks=1on the changed paths, on the main thread and in workers.JSON.stringifyandBun.inspectofprocess.envare the same as before for empty, non-ASCII, numeric and__proto__names, and forTZset, empty and not set.#if OS(WINDOWS)statements on macOS with the conditions inverted. I did not run them on Windows.no test proof · iteration 1 · platform-specific test(s) that do not run on this machine, deferring to CI, which covers all platforms: test/js/node/process/process.test.js