facebookarchive/prepack

CompilerDiagnostics in visitor or serialize cause crash

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#2072 opened on Jun 1, 2018

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bughelp wantedpriority: lowserializer

Description

Prepacking this...

let c = __abstract("boolean", "(c)");
let obj = {};
if (c) Object.freeze(obj);
global.obj = obj;

Causes Prepack to crash:

~/git/prepack$ node lib/prepack-cli.js /tmp/test2.js
Errors found while prepacking
In input file /tmp/test2.js(2:11) RecoverableError PP9000: Object that might or might not be sealed or frozen are not supported in residual heap. (https://github.com/facebook/prepack/wiki/PP9000)
Invariant Violation: undefined
This is likely a bug in Prepack, not your code. Feel free to open an issue on GitHub.
    at invariant (/Users/nikolait/git/prepack/lib/invariant.js:22:15)
    at statistics.total.measure (/Users/nikolait/git/prepack/lib/serializer/serializer.js:205:31)
    at PerformanceTracker.measure (/Users/nikolait/git/prepack/lib/statistics.js:90:14)
    at Serializer.init (/Users/nikolait/git/prepack/lib/serializer/serializer.js:115:35)
    at prepackSources (/Users/nikolait/git/prepack/lib/prepack-standalone.js:85:33)
    at prepackFileSync (/Users/nikolait/git/prepack/lib/prepack-node.js:163:49)
    at run (/Users/nikolait/git/prepack/lib/prepack-cli.js:384:24)
    at Object.<anonymous> (/Users/nikolait/git/prepack/lib/prepack-cli.js:471:3)
    at Module._compile (module.js:652:30)
    at Object.Module._extensions..js (module.js:663:10)

Note that it's okay to not support conditionally frozen objects; that's not the problem here. The problem is that it causes Prepack to crash with an invariant violation.

Contributor guide

Tech stack
javascript
Domain
tooling
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
JavaScriptNode.jsPrepack internals
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
The crash occurs in serializer.js line 205 during Serializer.init after a RecoverableError about conditionally frozen objects. Investigate how the visitor and serializer handle conditional Object.freeze by examining the error path in the compiler diagnostics. The fix likely involves ensuring that invariant violations are not triggered for unsupported but recoverable cases. Review the code in lib/serializer/serializer.js and lib/prepack cli.js to understand the flow.