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C++26 Reflection — hands-on blog series

A runnable, example-driven walkthrough of C++26 static reflection (P2996 and friends), built on a pinned bloomberg/clang-p2996 Docker image.

Every post has working code you can compile and run in under a minute. Every example is also mirrored on Compiler Explorer so you can play without installing anything.

Try it now

Option A — Compiler Explorer (zero install)

Each post's examples/godbolt.md lists permalinks. Click, edit, share.

Option B — Local container (arm64 or x86_64 Linux/macOS)

Requires Docker (or Colima/OrbStack on macOS). Build once, then use the wrappers.

./build.sh                              # 30-60 min, one-time; arm64-native
./cpp hello_reflection.cpp -o hello     # compile with clang-p2996
./run ./hello                           # run inside the container

Toolchain: pinned to bloomberg/clang-p2996@9ffb96e3ce36. The Dockerfile builds LLVM for AArch64 only with minimal components to keep build time and image size reasonable.

All examples compile with:

clang++ -std=c++26 -freflection -stdlib=libc++ ...

which is what ./cpp wraps.

The series

Status legend: ⬜ planned · 🚧 drafting · ✅ published

Arc 1 — Foundations

# Post Audience Status
1 Why C++26 reflection matters Polyglot ⬜
2 Your first ^^: reflecting types, walking members Mixed ⬜
3 Splicing: [: r :] and round-tripping reflections Working C++ ⬜
4 template for: iterating reflections at compile time Working C++ ⬜

Arc 2 — Everyday wins (lib/reflect_print)

# Post Audience Status
5 Goodbye magic_enum: enum reflection done right Working C++ ⬜
6 Auto-generating std::formatter<T> for any aggregate Working C++ ⬜
7 Deriving equality, hashing, and ordering from structure Working C++ ⬜

Arc 3 — Serialization (lib/reflect_json)

# Post Audience Status
8 A 40-line JSON serializer with reflection Working C++ ⬜
9 Annotations: tag-driven serialization in C++ Working C++ ⬜
10 Deserialization and std::expected error paths Working C++ ⬜
11 One codegen, many wire formats: YAML, TOML, MessagePack Working C++ ⬜

Arc 4 — Ambitious ports

# Post Audience Status
12 CLI parsing: struct → typed command-line parser Working C++ ⬜
13 A tiny ORM: struct → SQL Working C++ ⬜
14 Autowired dependency injection Working C++ ⬜
15 Auto-generated mocks from interfaces Working C++ ⬜

Arc 5 — Advanced / synthesis

# Post Audience Status
16 define_aggregate: synthesizing types at compile time Working C++ ⬜
17 Replacing Qt's MOC with reflection Working C++ ⬜
18 Capstone: C++26 reflection vs Rust, C#, Java, TS, Go, Python Polyglot ⬜

News shorts (posts/00-news/)

Alongside the numbered series, dated news shorts under posts/00-news/ track what is happening in C++ right now, each with a runnable Compiler Explorer link. The series teaches reflection top-to-bottom; the news track is broader. As of June 2026 it spans all three C++26 pillars and their neighbours, not just reflection + safety:

Shorts that need a Compiler Explorer library or extra file (e.g. stdexec, an #embed asset) carry a // verify: ce-libs: or // verify: ce-file: header marker; verify.sh skips those locally and they are gated on Compiler Explorer instead.

How to follow

  • Star the repo; each published post ships as a tagged release (post-01, post-02, ...).
  • Every post links to a GitHub Discussion thread — that's where questions and corrections live.
  • Issues are reserved for bugs in example code or the Docker toolchain.

Caveats

  • The Bloomberg fork is explicitly not production-ready per its own README. Use it to learn and experiment with P2996, not to ship.
  • The pinned SHA will bump periodically as P2996 evolves. Old posts link to specific SHAs so historical examples always compile.
  • Annotations (P3394) syntax may change; posts that depend on annotations name the exact SHA they were verified against.

Local verification

./verify.sh walks every post's examples/ directory, compiles + runs each sample, and prints pass/fail. Required before tagging a release.

License

Code examples: MIT. Prose: CC BY 4.0.