C++26 Is Getting Compile-Time Reflection — and That’s a Big Deal

Daniel Lemire is a software performance expert. He ranks among the top 2% of scientists globally (Stanford/Elsevier 2025) and is one of GitHub’s top 1000 most followed developers.

Recently he wrote a blog post entitled Discover C++26’s compile-time reflection. Indeed, Java, C#, and indeed Python fans will be delighted: C++26 is getting compile-time reflection – and that’s a big deal.

Herb Sutter has confirmed it: C++26 will ship with compile-time reflection. This is one of the most important upgrades to C++ in decades.

What is reflection (in plain terms)?

Reflection means code that can see and reason about itself.

Given a type, you can:

• List its data members
• Get their names and types
• Generate code based on that structure

Languages like Java, C#, and Python have had reflection forever — but usually at runtime, with performance and safety costs.

C++ is doing something different.

What makes C++ reflection special?

C++26 reflection is compile-time.

That means:

• No runtime overhead
• No stringly-typed hacks
• Fully type-checked
• Optimized away by the compiler

You’re not inspecting objects while running — you’re generating code while compiling.

Why should C++ programmers care?

Because it kills boilerplate.

Example: JSON serialization

Today, mapping a struct to JSON means:

• Writing manual serializers
• Maintaining them forever
• Debugging mismatches

With compile-time reflection, libraries like simdjson can do this automatically:

struct kid {
  int age;
  std::string name;
  std::vector<std::string> toys;
};

kid k{12, "John", {"car", "ball"}};

simdjson::to_json(k);
// {"age":12,"name":"John","toys":["car","ball"]}

kid k2 = doc.get<kid>();

No macros. No annotations. No runtime reflection tax.
The mapping is generated at compile time and heavily optimized.

Example: Object → SQL mapping (ORM without the pain)

Take a simple struct:

struct User {
  int id;
  std::string name;
  double balance;
private:
  int secret; // ignored
};

You want:

INSERT INTO tbl (id, name, balance)
VALUES (0, '', 0.000000);

With compile-time reflection, this becomes:

generate_sql_insert(user, "tbl");

What happens under the hood?

At compile time, the code:

• Enumerates all public data members
• Extracts their names
• Generates the column list as a compile-time string
• Emits efficient formatting code for values

The SQL string is largely precomputed during compilation.

Why this matters architecturally

This unlocks a new style of C++ programming:

• Zero-boilerplate serialization
• Type-safe code generation
• One implementation, reused everywhere
• Library-level correctness instead of copy-paste bugs

You write the hard logic once, test it thoroughly, and every type benefits.

“But the code looks scary…”

Yes — reflection syntax is new and template-heavy.

But:

• Most users won’t write this code
• Library authors will
• End users get clean, simple APIs

Exactly like STL, ranges, or allocators: scary inside, elegant outside.

Bottom line

C++26 compile-time reflection means:

• Less glue code
• Fewer macros
• Better performance
• More correctness
• Cleaner APIs

In the next few years, expect:

• Simpler serializers
• Better ORMs
• Smarter bindings
• Safer metaprogramming

This is C++ doubling down on what it does best: abstraction without overhead.

If you care about modern C++ design — this is one of the biggest wins coming your way.

For details, read Daniel’s post.