A realm now has String, Number, RegExp and Date as ECMAScript 5.1
sections 15.5, 15.7, 15.9 and 15.10 define them, with Annex B's substr,
getYear, setYear and toGMTString.
- String: every ES5 prototype method; split, replace, match and search
take strings and RegExps. Each new string's length is checked against
the heap limit before it is built, and scans take fuel.
- Number: toString(radix), toFixed, toExponential and toPrecision
format from the number's exact decimal value.
- RegExp: a backtracking matcher keeps its choice points and capture
state on the heap, within the heap room left, and takes fuel for every
step, so a catastrophic pattern stops at the fuel limit. Patterns
nested past Options::max_depth give a SyntaxError. Flags g, i and m,
lastIndex, exec, test and toString.
- Date: chrono converts days to calendar dates, shifting by whole
400-year cycles past its years. Realm::set_clock and
Realm::set_time_zone set the clock and local time (UTC by default).
Without a hint, a Date converts to a primitive as a string.
cargo xtask test262 also runs the suite's built-ins tests for the four
and prints their counts.
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.
A collection counts each piece of code a closure or frame keeps: its instructions, tables,
names, nested functions and its source text, each shared buffer once. Code that eval and the
Function constructor compile at run time is charged when it is made, after a heap reservation.
Function.prototype.toString reserves and charges the text it copies.
vectorcraft-js gains a Realm that runs ECMAScript 5.1 scripts. The parsed
script compiles to stack-machine bytecode, a verifier checks every jump
target, handler, constant index and stack depth before the code runs, and
the interpreter keeps JavaScript calls on its own frame stack. Closures,
this, arguments, with, direct and indirect eval, new Function,
try/catch/finally, labeled break and continue, and for-in in insertion
order follow sections 10 to 14 of ECMA-262 5.1. Variable references are
resolved before the right-hand side of an assignment runs (11.13).
Objects and environments live in an arena with a mark-and-sweep
collector and index handles. Built-ins are limited to Object and
Object.prototype's basic methods, Function with call and apply, eval
and the error constructors.
Every run is bounded by fuel, heap bytes, frames, nested host calls and
an interrupt flag another thread can set, with smaller defaults in the
wasm build. A run that reaches a limit ends with a limit error that a
script's try cannot catch. Source passed to eval and Function counts
against Options::max_source_units.
cargo xtask test262 also runs the suite's ES5 test/language tests that
need only these built-ins and prints their counts apart from the parse
counts. Nothing in the app calls the interpreter yet.
New crate vectorcraft-js reads ECMAScript 5.1 source into a syntax tree
with source positions: a UTF-16 lexer (line and column tracking, automatic
semicolon insertion, the regexp and division goals), preprocessor lines
read as directive tokens, a recursive-descent parser to an arena tree, and
the ES5 early errors, strict mode included. Nesting deeper than
Options::max_depth (200 by default) gives a SyntaxError with its line and
column rather than overflowing the stack. Nothing runs scripts yet.
cargo xtask test262 downloads test262 at a pinned commit, checks its
SHA-256, unpacks it into the gitignored corpus/ folder and runs the ES5
syntax tests. A differential test in the engine compares the lexer with
scriptcheck on line counts, directives and unterminated literals.
dotCooCoo