May 23, 2026
AST-la vista, confusion
Show HN: Anyone interested in a tool helps to explore C++ ASTs
Code nerds spot a new x-ray for giant software projects — and instantly ask who inspired it
TLDR: ACAV is a new visual tool that helps people explore the hidden structure of large C and C++ projects by clicking around instead of drowning in raw code internals. The community reaction was instantly curious and slightly skeptical, with commenters zeroing in on one big question: is this genuinely new, or part of an older tool family?
A new project called ACAV just dropped onto Hacker News with a very specific promise: take the tangled insides of big C and C++ codebases and turn them into something people can actually browse, click through, and understand. In plain English, it’s a visual map for the hidden structure of source code, built for people who want to peek under the hood without getting lost immediately. It can open a real project, show the tree of how the code is understood by the compiler, jump between the code and that tree, and save work so it doesn’t have to rebuild everything every time.
But in true internet fashion, the tool itself was only half the show — the comment-section energy was the real headline. The creator popped in with a casual “here’s the repo” and a friendly “ask me anything” vibe, which gave the thread that wholesome indie-launch feel. Then came the first sharp community instinct: wait, is this connected to Kythe? That single question basically set the tone. Instead of pure applause, readers immediately switched into detective mode, trying to place ACAV in the family tree of existing code-exploration tools.
There wasn’t a full-on flame war here, but there was that classic Hacker News tension: is this fresh and useful, or is it the new kid arriving to be compared with an older, more established project? The humor is subtle, but the mood is very “cool demo, now explain your lineage.” In other words: even when someone builds a shiny viewer for code structure, the crowd still wants the origin story, the receipts, and maybe a tiny bit of drama.
Key Points
- •ACAV is an interactive AST visualization tool for C, C++, and Objective-C built with Clang and Qt.
- •The tool uses a JSON compilation database, such as compile_commands.json, to open real projects and inspect translation-unit ASTs.
- •ACAV supports bidirectional navigation between source locations and AST nodes, declaration-context viewing, search, and reuse of dependency and AST-cache artifacts.
- •Its architecture consists of three programs: acav for the GUI, query-dependencies for dependency extraction, and make-ast for building and caching serialized AST files.
- •The tool is designed for read-only AST exploration of one translation unit at a time and is intended for students, researchers, and developers working with Clang-based tools.