The text a non-string argument converts to stays rooted while the parse runs, so a
collection still counts it. A property name read from the text is charged to the heap
until its property is defined. Boolean.prototype.toString and valueOf are added, so a
Boolean object writes `true` or `false`. The json2 sample no longer includes U+2028:
the polyfill escapes it and section 15.12.3 does not.
Installing the built-ins is not bounded by the heap limit: Math and JSON
no longer reserve heap while they install, so a realm made with a tiny
heap_bytes gets every built-in and runs once the limit is raised. If
installing fails, the realm keeps the reason and every run ends with an
internal error instead of running against missing built-ins.
The json2.js test skips only when the built-in check returns false, and
fails on any other result. The parser's progress line says the app does
not run scripts yet.
vectorcraft-js now provides the ECMAScript 5.1 built-ins: the Object
property-descriptor functions, create, keys, seal and freeze (15.2),
Function.prototype.bind (15.3.4.5), Array with every ES5 method (15.4),
the error types (15.11), Math (15.8), JSON with revivers, replacers and
indentation (15.12), and the global functions with Annex B's escape and
unescape (15.1, B.2). Prototype methods are writable and configurable.
The array methods work on array-like objects and visit only the indices
that exist, so a sparse array of length 2^32-1 costs as much as its
elements, and they see indices a callback adds. join writes a cycle back
to an array as an empty string; JSON.stringify throws a TypeError on a
cycle. JSON parsing, writing and the reviver walk use no native
recursion. Every loop takes fuel and every result is checked against
the heap limit, so new Array(4294967295).join("x") ends with the heap
limit and a huge sort or stringify ends with a limit.
cargo xtask test262 also runs the suite's ES5 built-in tests and fetches
json2.js at a pinned commit, checked against its SHA-256, to compare its
output with the built-in JSON once Date, String.prototype.replace and
RegExp exist.
dotCooCoo