Release Notes
v0.6.0 is the one of the largest releases since the project began. 56 commits touching 73 files with over 8,000 lines of new code. Three core data structures have been replaced: strings now use ropes, arrays use dense backing buffers, and the tokenizer caches streams per function body. The garbage collector gained conservative stack scanning and controlled safepoints, and the runtime now performs tail call optimization. This is effectively a new engine underneath the same API.
We also now have a discord: http://discord.gg/CH7YSjWGzY
Rope Strings
String concatenation now uses a rope data structure for deferred flattening:
let s = '';
for (let i = 0; i < 10000; i++) {
s += 'x'; // O(1) concatenation via rope nodes
}
- Flattening deferred until string content is actually read
- Max depth of 64 with automatic flattening at 32KB threshold
Dense Arrays
Arrays now use a dense backing store for indexed elements:
const arr = [1, 2, 3, 4, 5]; // Stored as contiguous jsval_t buffer
arr.push(6); // Appends to dense buffer
arr[100] = 'sparse'; // Falls back to property storage
Token Streaming Cache
Function bodies are now tokenized once and replayed on subsequent calls:
token_stream_t caches token type, offset, length, and literal values- Cached per-function via
parsed_func_t hash table
Tail Call Optimization
Recursive functions in tail position are optimized to reuse the current call frame:
function factorial(n, acc = 1n) {
if (n <= 1n) return acc;
return factorial(n - 1n, n * acc); // Tail call: no stack growth
}
factorial(10000n); // Works without stack overflow
- Token stream scanned at parse time to detect tail call patterns
scan_tail_span() analyzes return statements for eligible calls
GC Safepoints & Stack Scanning
Garbage collection now uses controlled safepoints and conservative stack scanning:
- Engine now marks safe points for collection
- GC scans C stack for heap pointers reducing manual rooting overhead
- Expression operands rooted across sub-expression evaluation
- Adaptive cooldown tuned for heap size (2-8 second intervals)
- GC throttling during server response handling and coroutine execution
- Promise offset tracking prevents premature collection of pending promises
BigInt Bitwise Shifts
BigInt now supports left and right shift operators:
const a = 1n << 64n; // 18446744073709551616n
const b = 256n >> 4n; // 16n
- Optimized fast path for values fitting in
uint64_t
- Arbitrary-precision fallback using multiply/divide by powers of 2
Class Computed Property Keys
Classes now support computed property names for fields, methods, and static members:
const key = 'x';
class Vec {
[key] = 0;
['get' + 'Value']() { return this.x; }
static ['create']() { return new Vec(); }
}
const sym = Symbol('id');
class Entity {
[sym] = 42;
}
new Entity()[sym]; // 42
- Computed keys evaluated once at class definition time
- Symbol, string, and numeric keys supported
- Side-effect expressions (
[makeKey()]) only run during class creation
ES6 Feature Additions
Symbol.species for subclass constructor customizationObject.is() for same-value equalityNumber.parseInt / Number.parseFloat aliasesPromise.race() and Promise.all() accept any iterable- Proxy support for
push, pop, splice, includes, indexOf, and instanceof
- Static class members properly initialized
Stdin Piping
Ant now reads from stdin when no file argument is given:
echo "console.log('hello')" | ant
cat script.js | ant
Unified Event Loop
All async modules now share uv_default_loop() directly:
- Removes per-module private event loops (fs, fetch, child_process)
- Fixes deadlocks when async operations ran on unpolled loops
- Server integration via
js_reactor_set_poll_hook()
- Per-emitter event tracking via
emitter_registry
Unified String Handling
New js_to_cstr() API for safe value-to-C-string conversion:
char buf[512];
js_cstr_t str = js_to_cstr(js, value, buf, sizeof(buf));
printf("%s\n", str.ptr);
if (str.needs_free) free((void *)str.ptr);
- Stack buffer fast path avoids allocation for small strings
- Automatic heap fallback for large values
- Eliminates memory leaks from
tostr_alloc() call sites
Absolute Path Imports
ES modules now resolve absolute paths with extension probing:
import config from '/etc/myapp/config.js';
- Tries
.js, .ts, .mts, .cts, .json extensions
- Consistent with relative path resolution behavior
URL Module Prototype Migration
The URL constructor now uses proper prototype-based methods:
- Methods like
toString(), toJSON() moved to URL.prototype
SLOT_ENTRIES for search params iterator statejs_eval_cached() API for snapshot-based evaluation
Additional Changes
- Arena shrinking and memory decommit for reduced RSS
- Interned property cache invalidated by generation counter on GC
- Weak reference handling for collections GC updates
- Dedicated descriptor entry for array
length property
- Reactor event polling optimized for fewer wakeups
- Consolidated runtime cleanup logic
- Child process event loop detection and polling improvements
- Event system memory cleanup on emitter teardown
- Comprehensive BUILDING.md guide added
To install Ant v0.6.0
curl -fsSL https://ant.themackabu.com/install | bash
# or with MbedTLS (darwin only)
curl -fsSL https://ant.themackabu.com/install | MBEDTLS=1 bash