Go Struct Analyzer — v2.0.4

A VS Code extension that shows memory size and padding information for Go structs, now powered by a Go LSP backend for exact fieldalignment parity.

Features

• Hover Information — hover over struct fields to see size, alignment, offset, and padding
• Inline Annotations — code lens showing struct/field sizes and GC scan info directly in the editor
• Optimization Warnings — real-time yellow underline when struct layout wastes memory
• GC Pressure Hints — blue underline when pointer field reordering reduces GC scan range
• Quick Fix — one-click reorder for memory layout and GC pressure issues (preserves tags, comments, indentation)
• Side Panel — side-by-side Current and Optimal layouts
• Architecture Support — configurable target (amd64, 386, arm64, arm)

Quick Install

code --install-extension PatricioDiaz.go-struct-analyzer

Install from VSIX (VS Code / Cursor)

Download the .vsix from GitHub Releases:

code --install-extension go-struct-analyzer-*.vsix

Cursor: Extensions → "..." → Install from VSIX.

Quick Start

Open any Go file. Hover over a struct field to see its layout. When a struct shows a yellow warning, click the lightbulb or press Ctrl+. to reorder fields for optimal size:

type Event struct {         // ⚠️ 40 bytes (can be 24 bytes)
    A bool     // 1B
    B int64    // 8B (+7B padding)
    C bool     // 1B
    D int64    // 8B (+7B padding)
    E int32    // 4B
    F bool     // 1B (+3B padding)
}

After quick fix:

type Event struct {         // ✓ 24 bytes, -16B
    B int64    // 8B
    D int64    // 8B
    E int32    // 4B
    A bool     // 1B
    C bool     // 1B
    F bool     // 1B (+1B padding)
}

gsa-lsp CLI Tool

The extension ships gsa-lsp — a standalone Go binary for struct analysis outside VS Code:

gsa-lsp analyze [--arch amd64] file.go     # JSON output
gsa-lsp lsp                                 # LSP server (stdin/stdout)
gsa-lsp version                             # version info

Install from source:

make build-go                               # builds gsa-lsp to project root
make install                                # copies to $GOPATH/bin

Install via curl (recommended):

curl -fsSL https://padiazg.github.io/go-struct-analyzer/install.sh | sh

Install a specific version:

curl -fsSL https://padiazg.github.io/go-struct-analyzer/install.sh | sh -s -- -v v2.0.4

LSP Server for Other Editors

gsa-lsp is a standard LSP server — use it with any LSP-compatible editor alongside gopls:

gsa-lsp lsp                                 # stdin/stdout JSON-RPC

Supported LSP methods: textDocument/hover, textDocument/codeLens, textDocument/codeAction, textDocument/publishDiagnostics.

Emacs: see the Emacs setup guide for eglot (Emacs 29+) and lsp-mode.

Neovim: see the Neovim setup guide for built-in LSP client config.

Helix (~/.config/helix/languages.toml):

[language-server.gsa-lsp]
command = "gsa-lsp"
args = ["lsp"]

[[language]]
name = "go"
language-servers = ["gsa-lsp"]

Zed (experimental): install the dev extension from editors/zed/ via zed: install dev extension. See editors/zed/README.md. The binary must be on PATH.

Best experience is the VS Code extension (inline annotations, side panel). Other editors get hover info, diagnostics, and code actions only.

Configuration

Setting	Default	Description
showInlineAnnotations	false	Show size annotations inline
showPadding	true	Highlight padding bytes
architecture	amd64	Target architecture
enableStructOptimizationWarnings	true	Warnings for sub-optimal layout
enableReorderCodeAction	true	Quick fix for field reorder
reorderCodeActionPreferred	false	Enable source.fixAll
enableGCPressureWarnings	true	GC scan range hints
gcPressureSeverityWarning	false	GC hints as warnings (yellow underline) instead of hints (...)

All settings are prefixed with goStructAnalyzer. (e.g. goStructAnalyzer.architecture).

Documentation

• Full user documentation — detailed guides for all features
• Configuration — all settings reference
• Memory alignment concepts — how Go struct alignment works
• GC scan range — understanding GC pressure

Build from Source

git clone https://github.com/padiazg/go-struct-analyzer
cd go-struct-analyzer
make build                                    # Go binary + TypeScript
# or:  make build-go                          # Go binary only
# or:  make build-ts                          # TypeScript only

Prerequisites: Go 1.21+, Node.js 22+

Contributing

See CONTRIBUTING.md for setup, project structure, coding guidelines, and PR process.

Changelog

See changelog.md for version history.

v2.0.4: Server version compatibility check — extension stops if gsa-lsp major version mismatches. curl installer served from GitHub Pages.

License

MIT — see LICENSE.

Acknowledgments

• fieldalignment — the GC pointer scan range concept that inspired the GC pressure analysis.