Assertion failure in JavascriptArray.cpp

Description

function opt(){
	const v2 = [-1000000000.0];
	v2.length = 4294967295;
	const v3 = v2.copyWithin();
	return v3;
}


for(let i=0;i<0x200;i++){
	opt(false);
}

Contributor guide

Tech stack

cppjavascript

Domain

backend

Issue type

bug

DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.

5

Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.

over 1 week

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.

clear

Prerequisites

C++debuggingJavaScript engine internals

Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.

10

Research direction

Reproduce the assertion failure in debug build using the provided POC. Investigate the copyWithin function in JavascriptArray.cpp to understand why it fails for the given array with large length. The fix likely involves bounds checking or proper handling of integer overflow.