Design_Guidelines.md

C++ Design Guidelines

Linkage

Utility functions

Avoid free functions (except operator functions) at file scope in .h files; avoid free functions with external linkage (including operator functions) in .cpp files.

1. Free functions with user defined type arguments:
2. Classes that holds utility functions as static member functions

Enumerations, typedefs

• Prefer scoped enum to unscoped enum
• If unscoped enum is have to be used, define within class to keep the global namespace cleaner.

class MyClass
{
    public:
        enum Color {BLACK, RED, GREEN}

};

Inline functions

• Member or free inline functions should be defined in header files.

Macros

• Avoid preprocessor macros in header files except include guards

Class Design

• const methods should not return non-const references or pointers

class MyClass
{
    public:
        B& GetB() const; // BAD
        const B& GetB() const; // GOOD: Non-mutable
        B& GetB(); // OK: Mutable
};

Inheritance

• Prefer protected methods rather than protected fields: It is as bad as public since it is giving access to its internals to its child class.

Casting

• Prefer modern style C++ casting over C style casting
• dynamic_cast<T>(arg) will not work if Copy Ctor is deleted or private for type of arg. (E0330, C2248)

Implicit type conversions

• Implicit type conversion never happens on the implicit parameter, this, for member functions so consider non-member overloading if implicit type conversion is desired. [Meyers - Effective C++, Item 24]

class MyClass
{
    public:
    MyClass(int){/*...*/}
    const MyClass operator*(const MyClass &rhs){/*...*/};

};

auto obj =  MyClass{};
auto result = obj * 2; // WORKS
auto result2 = 2 * obj; //ERROR - no implicit type conversion if not

• Implicit type conversion functions (also ctors) are never considered during template argument deduction.