Go Memory Layout Visualizer

See the padding Go inserts. Reorder in one click.
Inline annotations · visual byte map · pack score · cache lines · amd64/arm64/386

Install: ext install RhinoSoftware.go-memory-visualizer
Or: Marketplace · Open VSX · Website

30 seconds to “oh”

type Sparse struct {
    Active bool    // 1B + 7B padding
    ID     uint64
    Tag    uint8   // 1B + 7B padding
    Name   string
}
// 40B · pack 65% · 14B wasted

Open the file → annotations appear → click Optimize Layout (save 8B · pack 65%):

Sparse  40B  pack 65%  pad 14B
0000  A.......BBBBBBBB
0010  C.......DDDDDDDD
0020  DDDDDDDD
legend: A=Active  B=ID  C=Tag  D=Name  .=padding

After reorder: 32B · pack 85% · saved 8 bytes. Same fields, less air.

Why people install this

Spot padding without running unsafe.Sizeof or reading the Go ABI by hand
Cut struct size 10–30% on hot types (API responses, events, DB models)
Teach juniors (and yourself) how alignment actually works
Paste the ASCII map into a PR when you want reviewers to see the waste

Features

Real-Time Analysis

Inline annotations showing memory details for each field
Byte offsets so you know exactly where fields live
Size calculations and alignment requirements
Padding detection with visual warnings

Visual Feedback

Color-coded warnings for excessive padding
Cache line boundary detection (64-byte warnings)
Hover tooltips with detailed breakdowns
CodeLens buttons for one-click optimization

Optimization Tools

Automatic field reordering by alignment and size
Shows exact bytes saved before and after
Preview before rewrite (current vs proposed order + pack score)
Preserves your comments and struct tags
Safe refactoring that doesn't break anything
Works with nested and embedded structs
Keeps grouped field lines intact when optimizing

Visual Memory Map (new in v1.1)

Byte-level colored grid for the struct under the cursor
ASCII map you can paste into reviews or docs
Pack score: how much of the struct is real data vs padding

Export and Reporting

Export memory layout reports to JSON, Markdown, or CSV
Detailed field-by-field analysis with offset, size, alignment, and padding information
Architecture-specific reports for cross-platform analysis
Perfect for documentation, code reviews, and performance audits

v1 Accuracy

Same-file type aliases and alias blocks resolve to their underlying Go types
Slices use Go's three-word slice header size on each supported architecture
complex64 uses 8 bytes with 4-byte alignment, matching Go's layout rules
error and any same-file type X interface { ... } declarations are sized as 2-word interface values (16 bytes amd64/arm64, 8 bytes 386)
Anonymous inline struct fields (Inner struct { ... }) are parsed and sized recursively, including multi-line declarations
unsafe.Pointer is treated as a pointer-sized value

Multi-Architecture Support

Supports amd64, arm64, and 386. Switch between them to see how pointer sizes affect layout.

Installation

From VS Code Marketplace

Open VS Code
Press Ctrl+P (Windows/Linux) or Cmd+P (Mac)
Type: ext install RhinoSoftware.go-memory-visualizer
Press Enter

Or visit the VS Code Marketplace

From Source

git clone https://github.com/1rhino2/go-memory-visualizer.git
cd go-memory-visualizer
npm install
npm run compile
code .
# Press F5 to launch Extension Development Host

Quick Start

1. Open a Go File

Create or open any .go file with struct definitions:

type User struct {
    Active    bool    //  1 byte + 7 padding
    ID        uint64  // 8 bytes
    Name      string  // 16 bytes
    Age       uint8   //  1 byte + 7 padding
    Balance   float64 // 8 bytes
}

2. See Instant Analysis

The extension automatically shows:

// offset: 0 | size: 1 | align: 1 | padding: 7 
Active    bool

// offset: 8 | size: 8 | align: 8 | padding: 0
ID        uint64

// Total: 48 bytes | Padding: 14 bytes (29% waste)

3. Optimize with One Click

Click the CodeLens button above the struct:

 Optimize struct - save 14 bytes (29% reduction)

4. See Optimized Result

type User struct {
    ID        uint64  // 8 bytes (no padding)
    Balance   float64 // 8 bytes (no padding)
    Name      string  // 16 bytes (no padding)
    Active    bool    // 1 byte (no padding)
    Age       uint8   // 1 byte + 6 final padding
}
// Total: 40 bytes | Padding: 6 bytes (15% waste)
//  Saved 8 bytes (16.7% reduction)

Commands

Access via Command Palette (Ctrl+Shift+P / Cmd+Shift+P):

Command	Description
`Go: Show Memory Layout`	Display detailed memory breakdown for all structs
`Go: Show Visual Memory Map`	Byte-level colored map + ASCII for the struct at cursor
`Go: Optimize Struct Memory Layout`	Reorder fields in struct at cursor to minimize padding
`Go: Toggle Architecture`	Switch between amd64, arm64, and 386
`Go: Export Memory Layout Report`	Export struct analysis to JSON/Markdown/CSV
`Go: Analyze Workspace Memory Layout`	Scan the workspace for padding and cache line issues
`Go: Compare Struct Layout Across Architectures`	Side-by-side amd64/arm64/386 layout for the struct at cursor

Optimization is also available as a Quick Fix (Ctrl+. / Cmd+.) on any struct that can be reordered for savings, and the status bar shows the total bytes saveable in the current file at a glance. High-padding, optimization-eligible, and cache-line-crossing structs are surfaced in the Problems panel via diagnostics.

Configuration

Customize via VS Code Settings (Ctrl+, / Cmd+,):

{
  // Default architecture for memory calculations
  "goMemoryVisualizer.defaultArchitecture": "amd64",
  
  // Show inline annotations above struct fields
  "goMemoryVisualizer.showInlineAnnotations": true,
  
  // Highlight fields with excessive padding
  "goMemoryVisualizer.highlightPadding": true,
  
  // Minimum padding bytes to trigger warning (default: 8)
  "goMemoryVisualizer.paddingWarningThreshold": 8,
  
  // Show warnings for cache line boundary crossings
  "goMemoryVisualizer.showCacheLineWarnings": true,

  // Ask before rewriting field order (shows before/after preview)
  "goMemoryVisualizer.confirmBeforeOptimize": true,

  // Size time.Time, sync.Mutex, atomic.*, etc. from known layouts
  "goMemoryVisualizer.useKnownStdlibTypes": true
}

Configuration Details

Setting	Type	Default	Description
`defaultArchitecture`	string	`"amd64"`	Architecture for calculations: `amd64`, `arm64`, or `386`
`showInlineAnnotations`	boolean	`true`	Display memory info above each field
`highlightPadding`	boolean	`true`	Highlight fields with padding waste
`paddingWarningThreshold`	number	`8`	Min padding bytes to show warning
`showCacheLineWarnings`	boolean	`true`	Warn about 64-byte cache line crossings
`confirmBeforeOptimize`	boolean	`true`	Preview before rewriting field order
`useKnownStdlibTypes`	boolean	`true`	Size time/sync/atomic/context from known layouts

Examples

See examples/structs.go for demonstrations of:

Well-optimized structs (minimal padding)
Poorly-optimized structs (excessive padding)
Common anti-patterns to avoid
Best practices for field ordering

Real-World Savings

API Response (56 to 48 bytes, 14% reduction)

Before:

type APIResponse struct {
    Success   bool      // 1 + 7 padding
    Timestamp int64     // 8
    Message   string    // 16
    Code      int32     // 4 + 4 padding
    RequestID string    // 16
}
// 56 bytes, 11 bytes wasted

After:

type APIResponse struct {
    Timestamp int64     // 8
    Message   string    // 16
    RequestID string    // 16
    Code      int32     // 4
    Success   bool      // 1 + 3 final padding
}
// 48 bytes, 3 bytes wasted

Impact: 1M responses = 8 MB saved

New in v0.2.0

Nested Struct Support

The extension now automatically calculates memory layout for structs containing other custom structs:

type Point struct {
    X float64 // 8 bytes
    Y float64 // 8 bytes
}

type Rectangle struct {
    TopLeft  Point  // 16 bytes (nested struct)
    Width    uint32 // 4 bytes
    Height   uint32 // 4 bytes
}
// Total: 24 bytes

The parser performs two-pass analysis:

First pass: Register all struct definitions
Second pass: Calculate layouts with nested struct sizes resolved

Embedded Field Handling

Embedded fields (promoted fields) are now properly detected and analyzed:

type Base struct {
    ID        uint64 // 8 bytes
    CreatedAt int64  // 8 bytes
}

type User struct {
    Base           // embedded: 16 bytes
    Name   string  // 16 bytes
    Active bool    // 1 byte + 7 padding
}
// Total: 40 bytes

Embedded pointers are also supported:

type Document struct {
    *Metadata         // embedded pointer: 8 bytes
    Title     string  // 16 bytes
    Published bool    // 1 byte
}

Export Memory Layout Reports

New command to export detailed struct analysis:

JSON Format: Machine-readable with full field details

{
  "structs": [{
    "name": "User",
    "totalSize": 40,
    "alignment": 8,
    "totalPadding": 7,
    "paddingPercentage": 17.5,
    "fields": [...]
  }],
  "architecture": "amd64",
  "exportedAt": "2025-11-23T12:00:00.000Z"
}

Markdown Format: Human-readable documentation

## User

- **Total Size:** 40 bytes
- **Alignment:** 8 bytes
- **Total Padding:** 7 bytes (17.5%)

### Fields

| Field | Type | Offset | Size | Alignment | Padding After |
|-------|------|--------|------|-----------|---------------|
| ID    | uint64 | 0    | 8    | 8         | 0             |

CSV Format: Perfect for spreadsheets and data analysis

Struct,Field,Type,Offset,Size,Alignment,Padding After,Total Size,Total Padding,Padding Percentage,Architecture
User,ID,uint64,0,8,8,0,40,7,17.5,amd64

Usage:

Open a Go file with struct definitions
Run command: Go: Export Memory Layout Report
Choose format: JSON, Markdown, or CSV
Save to desired location

Perfect for:

Code reviews and documentation
Performance audits
Cross-architecture analysis
Team collaboration

How It Works

Memory Layout Calculation

The extension follows Go's alignment rules:

Type Alignment: Each type has an alignment requirement:
- bool, int8, uint8: 1 byte
- int16, uint16: 2 bytes
- int32, uint32, float32: 4 bytes
- int64, uint64, float64: 8 bytes
- Pointers, strings, slices: 8 bytes (amd64/arm64), 4 bytes (386)
Field Placement: Each field starts at an offset aligned to its requirement
Padding Insertion: Go adds padding bytes to satisfy alignment
Final Padding: Struct size is rounded up to largest field alignment

Optimization Algorithm

1. Extract all fields from struct
2. Calculate current layout and total size
3. Sort fields:
   - Primary: by alignment (descending)
   - Secondary: by size (descending)
4. Recalculate layout with new ordering
5. Compare sizes and show savings

Testing

Run the comprehensive test suite:

npm test

Test Coverage:

52 automated tests across parser, calculator, optimizer, diagnostics, arch compare, memory map, and known stdlib types
CI runs compile, lint, and tests on Node 20 and 22

Documentation

DEMO.md: Interactive demonstrations and visual examples
DEVELOPMENT.md: Developer guide and architecture
CHANGELOG.md: Version history and release notes

Contributing

Contributions welcome! Please:

Fork the repository
Create a feature branch (git checkout -b feature/amazing-feature)
Commit changes (git commit -m 'Add amazing feature')
Push to branch (git push origin feature/amazing-feature)
Open a Pull Request

Development Setup

git clone https://github.com/1rhino2/go-memory-visualizer.git
cd go-memory-visualizer
npm install
npm run compile
npm test

Requirements

VS Code: 1.85.0 or higher
Go files: .go extension in workspace
Node.js: 20.x or higher (for development)

Known Issues

None for v1.0.0. Previous limitations resolved:

~~Nested struct support~~ ✅ Added in v0.2.0
~~Embedded struct handling~~ ✅ Added in v0.2.0
~~Same-file type aliases~~ ✅ Added in v1.0.0
Union type support (planned)

See GitHub Issues for full list.

License

MIT License - see LICENSE file for details.

Acknowledgments

Inspired by Go's memory layout documentation
Built with VS Code Extension API
Thanks to the Go community for feedback

Support

Issues: GitHub Issues
Discussions: GitHub Discussions
Contact: 1rhino2 on discord

Roadmap

v0.2.0 - Released 2025-11-23

Nested struct support
Embedded field handling
Export layout reports

v0.2.1 - Released 2025-11-26

Fixed export error handling
Updated deprecated API usage

v0.2.2 - Released 2025-11-26

Security fix: Patched path traversal vulnerability in export function
Added path validation and normalization
Implemented write verification and explicit file permissions

v0.3.0 - Released 2025-12-03

Cache line visualization: Shows which 64-byte cache line each field occupies
Cache line crossing detection: Warns when fields span multiple cache lines
Workspace analyzer: New command scans all Go files for optimization opportunities
Hot field detection for false sharing risks

v0.3.1 - Released 2025-12-05

Security update: Fixed 18 security vulnerabilities (3 critical, 4 high, 10 medium, 1 low)
XSS prevention with HTML/Markdown escaping
Content Security Policy for webviews
ReDoS protection with simplified regex patterns
Resource limits for workspace analyzer
See Security Advisory

v1.1.0 - Released 2026-07-15

Visual memory map (byte grid + ASCII)
Pack score in status bar, CodeLens, and exports
Optimize preview with confirm-before-rewrite
Known stdlib type sizes (time, sync, atomic, context)

Future

Union / sum-type visualization helpers
Bitfield visualization
Optional unsafe.Sizeof cross-check via gopls

Made for the Go community

Website • GitHub • Marketplace • Docs

Name		Name	Last commit message	Last commit date
Latest commit History 63 Commits
.github/workflows		.github/workflows
.vscode		.vscode
docs		docs
examples		examples
scripts		scripts
src		src
.gitignore		.gitignore
.vscodeignore		.vscodeignore
CHANGELOG.md		CHANGELOG.md
DEMO.md		DEMO.md
DEVELOPMENT.md		DEVELOPMENT.md
LICENSE		LICENSE
README.md		README.md
eslint.config.js		eslint.config.js
go-memory-visualizer.code-workspace		go-memory-visualizer.code-workspace
package-lock.json		package-lock.json
package.json		package.json
tsconfig.json		tsconfig.json

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