ferroalloc — Rust Memory Lens

Real-time heap memory visualization for Rust directly in VS Code.
See which lines allocate the most, detect leaks, and compare memory snapshots — without leaving your editor.

ferroalloc demo

Features

CodeLens — live allocation stats per line

Every line that allocates heap memory shows an inline counter:

allocate_buffer: 142 allocs · 72.7 MB        ← CodeLens
fn allocate_buffer() -> Vec<u8> {
    vec![0u8; 512 * 1024]
}

The counter updates every second while your program runs.
Lines with unreleased memory show a ⚠ warning icon.

Heatmap — visual allocation pressure

Background colors range from green (low) to red (high) based on total bytes allocated per line.

Leak detection

Ferroalloc: Show Live Leaks lists every source line that has allocated memory not yet freed, sorted by bytes leaked.

Snapshot diff

Run a baseline workload → Ferroalloc: Save Memory Baseline
Run a second workload
Ferroalloc: Show Diff Since Baseline — shows which lines increased, decreased, or are new

Status bar

A live byte counter in the status bar. Click to toggle tracking on/off.

Quick Start

1 — Add the probe to your Rust project

# Cargo.toml
[dependencies]
ferroalloc-probe = "0.1"

// src/main.rs
use ferroalloc_probe::{FerroAllocator, start_flush_thread};

#[global_allocator]
static ALLOC: FerroAllocator = FerroAllocator;

fn main() {
    start_flush_thread(7777);   // connect to the analyzer on port 7777
    // ... rest of your program
}

2 — Run the analyzer

cargo install ferroalloc-analyzer
ferroalloc-analyzer

The analyzer listens for your program on port 7777 and exposes an HTTP API on port 7778 for the extension.

3 — Start tracking in VS Code

Open your Rust project, then:

Cmd+Shift+P  →  Ferroalloc: Start Memory Tracking

Run your program. CodeLens counters appear on allocating lines within seconds.

Configuration

Setting	Default	Description
`ferroalloc.analyzerPort`	`7778`	HTTP port of the analyzer API
`ferroalloc.refreshIntervalMs`	`1000`	Polling interval in milliseconds
`ferroalloc.heatmapEnabled`	`true`	Show green-to-red background heatmap

Commands

Command	Description
`Ferroalloc: Start Memory Tracking`	Connect to analyzer, begin polling
`Ferroalloc: Stop Memory Tracking`	Stop polling, clear decorations
`Ferroalloc: Toggle Memory Tracking`	Start or stop
`Ferroalloc: Reset Collected Data`	Clear all data on the analyzer
`Ferroalloc: Show Live Leaks`	List lines with unreleased allocations
`Ferroalloc: Save Memory Baseline`	Snapshot current state for diffing
`Ferroalloc: Show Diff Since Baseline`	Compare current state to baseline

How it works

Your Rust app                Analyzer              VS Code Extension
─────────────────            ────────────          ──────────────────
FerroAllocator               ferroalloc-           ferroalloc
  (GlobalAlloc)   ─TCP─▶     analyzer      ─HTTP─▶ extension
  captures every             aggregates            CodeLens + heatmap
  alloc/dealloc              by file:line          + leak panel
  resolves symbol
  at runtime

The probe resolves source locations (file, line, function) inside your process using the runtime symbol table — this avoids ASLR/DWARF address mismatch issues on macOS.

Requirements

Rust toolchain (stable)
ferroalloc-analyzer running locally (see Quick Start)
VS Code 1.90+

License

MIT

Ferroalloc — Rust Memory Lens

hichammh