How to avoid overuse of runtime type information in C++ generic programming?

In C generic programming, alternatives to avoid overuse of runtime type information (RTTI) include: Template specialization: used to perform specific operations on a limited number of types. Type aliases: used to access type-specific information. Metaprogramming: used to calculate type-dependent values ​​at compile time. These alternatives avoid the performance overhead and code complexity of RTTI by determining type information at compile time.

How to avoid overuse of runtime type information in C generic programming

In C generic programming, sometimes you need to access Type-specific information, such as the size of the type or the name of the member function. This is possible using runtime type information (RTTI), but excessive use of RTTI can lead to performance overhead and increased code complexity.

To avoid overuse of RTTI, you can use the following alternatives:

Template Specialization

If you can only perform a specific operation on a limited number of types , you can use template specialization. For example:

template <typename T>
void print_size(T& value) {
  std::cout << "Size of " << typeid(T).name() << ": " << sizeof(value) << std::endl;
}

template <>
void print_size(std::string& value) {
  std::cout << "Size of string: " << value.size() << std::endl;
}

Type Alias

You can access type-specific information by defining a type alias. For example:

using StringSize = std::integral_constant<size_t, sizeof(std::string)>;
std::cout << "Size of string: " << StringSize::value << std::endl;

Metaprogramming

Use metaprogramming techniques to calculate type-dependent values ​​at compile time. For example:

template <typename T>
struct TypeTraits {
  static constexpr size_t size = sizeof(T);
};

std::cout << "Size of string: " << TypeTraits<std::string>::size << std::endl;

Practical case

Consider a shape class with the following interface:

class Shape {
public:
  virtual double area() const = 0;
};

Usually, you need to access area() The name of the function to output it in the log. Use RTTI to get it:

// 使用 RTTI 来获取 area() 函数的名称
std::string area_function_name = typeid(Shape).name() + "::area";

However, this introduces a performance overhead. We can avoid this by using type aliases:

// 使用类型别名来访问 area() 函数的名称
using AreaFunctionName = const char (&)[5];
static const AreaFunctionName area_function_name = "area";

This approach determines the function name at compile time, avoiding the overhead of RTTI.

By using these alternatives, you can significantly reduce the use of RTTI in C generic programming, thereby improving performance and code maintainability.

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