C++ Coding Standards (C++ Core Guidelines)

Comprehensive coding standards for modern C++ (C++17/20/23) derived from the C++ Core Guidelines. Enforces type safety, resource safety, immutability, and clarity.

When to Use

• Writing new C++ code (classes, functions, templates)
• Reviewing or refactoring existing C++ code
• Making architectural decisions in C++ projects
• Enforcing consistent style across a C++ codebase
• Choosing between language features (e.g., enum vs enum class, raw pointer vs smart pointer)

When NOT to Use

• Non-C++ projects
• Legacy C codebases that cannot adopt modern C++ features
• Embedded/bare-metal contexts where specific guidelines conflict with hardware constraints (adapt selectively)

Cross-Cutting Principles

These themes recur across the entire guidelines and form the foundation:

1. RAII everywhere (P.8, R.1, E.6, CP.20): Bind resource lifetime to object lifetime
2. Immutability by default (P.10, Con.1-5, ES.25): Start with const/constexpr; mutability is the exception
3. Type safety (P.4, I.4, ES.46-49, Enum.3): Use the type system to prevent errors at compile time
4. Express intent (P.3, F.1, NL.1-2, T.10): Names, types, and concepts should communicate purpose
5. Minimize complexity (F.2-3, ES.5, Per.4-5): Simple code is correct code
6. Value semantics over pointer semantics (C.10, R.3-5, F.20, CP.31): Prefer returning by value and scoped objects

Philosophy & Interfaces (P., I.)

Key Rules

DO

// P.10 + I.4: Immutable, strongly typed interface
struct Temperature {
    double kelvin;
};

Temperature boil(const Temperature& water);

DON'T

// Weak interface: unclear ownership, unclear units
double boil(double* temp);

// Non-const global variable
int g_counter = 0;  // I.2 violation

Functions (F.*)

Key Rules

Parameter Passing

// F.16: Cheap types by value, others by const&
void print(int x);                           // cheap: by value
void analyze(const std::string& data);       // expensive: by const&
void transform(std::string s);               // sink: by value (will move)

// F.20 + F.21: Return values, not output parameters
struct ParseResult {
    std::string token;
    int position;
};

ParseResult parse(std::string_view input);   // GOOD: return struct

// BAD: output parameters
void parse(std::string_view input,
           std::string& token, int& pos);    // avoid this

Pure Functions and constexpr

// F.4 + F.8: Pure, constexpr where possible
constexpr int factorial(int n) noexcept {
    return (n <= 1) ? 1 : n * factorial(n - 1);
}

static_assert(factorial(5) == 120);

Anti-Patterns

• Returning T&& from functions (F.45)
• Using va_arg / C-style variadics (F.55)
• Capturing by reference in lambdas passed to other threads (F.53)
• Returning const T which inhibits move semantics (F.49)

Classes & Class Hierarchies (C.*)

Key Rules

…