C++26 Standard Draft Finalized with Reflection, Memory Safety, Contracts, and Async Framework

C++26 Standard Features

The C++26 standard draft is now complete according to Herb Sutter, former chair of the ISO C++ standards committee. The finalized draft introduces four major areas of improvement.

Reflection

Reflection gives developers access to C++'s internal machinery, enabling the language to describe itself and generate code with no runtime overhead. This provides a solid foundation for metaprogramming and can simplify future language evolution by allowing new features to be expressed as reusable compile-time libraries.

As an example, reflection enables specialized syntax for declaring C++ interfaces:

class(interface) IFoo {
    int f();
    void g(std::string);
};

This gets translated into the classical interface declaration with virtual methods. The interface abstraction is part of cppfront, a compiler that builds to pure ISO C++, which includes other abstractions like:

• copyable for expressing a type with copy/move construction/assignment
• ordered for defining a totally ordered type with operator<=>
• union for a tagged union with names
• regex and more

Memory Safety

C++26 includes out-of-the-box elimination of undefined behavior when reading uninitialized local variables, as well as bounds safety for most standard library types including vector, span, string, and string_view.

These changes have already been deployed in production at Apple and Google across hundreds of millions of lines of C++ code. At Google alone, it has fixed over 1,000 bugs, is projected to prevent 1,000 to 2,000 bugs per year, and has reduced the segfault rate across the production fleet by 30%.

These benefits were achieved simply by recompiling existing code with the new compiler. In only seven cases was the compiler unable to analyze highly optimized code, requiring developers to use a fine-grained API to selectively opt out of memory safety in those specific parts.

Contracts

C++26 contracts bring defensive programming into the language, improving both functional and memory safety. They allow developers to express pre- and post-conditions that must not be violated across a method execution. Contracts move assertions into function declarations, making them visible to callers and static analysis tools.

C++ offers four ways to handle contract violations: ignore, observe, enforce, and quick enforce. The contracts also bring a native assertion mechanism that replaces C's assert macro.

Async Model: std::execution

C++26 introduces std::execution as a framework to express and control concurrency and parallelism. The three main abstractions are schedulers, senders, and receivers, which can be composed through a set of customizable asynchronous algorithms.

std::execution is designed to work with C++20 coroutines and makes it easier to write programs that use structured (rigorously lifetime-nested) concurrency and parallelism to be data-race-free by construction.

The two major C++ compilers, GCC and Clang, have already implemented most of C++26 features during the standardization process.