C++ C++23

Use these rules for C++23 code that handles untrusted data, owns native resources, or crosses process and network boundaries.

Type and interface safety

• Express ownership, nullability, bounds, and mutability in types instead of relying on comments or calling convention.
• Prefer narrow value types, scoped enums, and validated constructors for security-relevant states.
• Use std::span, ranges, and containers instead of passing an array as a pointer without a bound.
• Mark single-argument constructors other than copy and move constructors explicit unless implicit conversion is intentionally safe.
• Keep public interfaces small and reject invalid states before constructing domain objects.

Bounds and object representation

• Validate indexes, iterator ranges, offsets, counts, and byte sizes before access or allocation.
• Initialize scalar variables and buffer elements before reading or exposing them; std::make_unique_for_overwrite does not value-initialize the allocated objects.
• Do not dereference invalidated iterators, dangling views, null pointers, or pointers outside an object's lifetime.
• Avoid reinterpret_cast, type punning, placement construction, and manual layout unless isolated and reviewed.
• Use std::bit_cast only between supported representations and still validate any untrusted semantic value.
• Treat unions, packed structures, flexible wire layouts, and custom allocators as explicit trust boundaries.

Integer and size safety

• Check signedness, range, and units before converting external values to sizes, indexes, durations, or enum