Segfault in QV4::SimpleArrayData with a simple testcase

A simple testcase (see below for a more complex one with smaller arrays and smaller expected memory consumption):

import QtQuick 2.0

Item {
	Component.onCompleted: {
		var len = 3000000;
		var foo = new Array(len + 1).join('x');
		var chars = foo.split('');
	}
}

The `len` required to crash is dependent on the platform, e.g.

• On Android phone (Nexus 5x with Android 8), it's below 600000
• On my Linux setup, it's below 2100000

For comparison, Node.js/v8 memory consumption on this test with various lengths:

• 0 — 9 MiB (baseline)
• 600000 — 19 MiB
• 2100000 — 45 MiB

—

Allocating a single array is not the only way to reach the segfault, but that was the most simple testcase.

Here is a more complex one, involving smaller arrays and smaller expected memory consumption:

var foo, chars, i;
for (i = 0; i < 100; i++) {
	console.log(i)
	foo = new Array(i * 10000 + 1).join('x');
	chars = foo.split('');
}

That also works in an asynchronous way:

Timer {
	interval: 10
	running: true
	repeat: true
	property int i: 0
	onTriggered: {
		console.log(i)
		var foo = new Array(i * 10000 + 1).join('x');
		var chars = foo.split('');
		i++;
	}
}

On my Linux pc, it segfaults at about i~=30 (drifting a bit).