Static assertions are a helpful tool in C++ for catching errors during compilation. They ensure that certain conditions are met at compile time, allowing you to catch potential issues before running the code.

In C++11 and later, the static_assert keyword is used to perform static assertions.

Basic static assertions

You can use static_assert to enforce compile-time conditions. For example:

static_assert(sizeof(int) == 4, "int must be 4 bytes");

The code above will trigger a compilation error if the size of int is not 4 bytes.

Improved syntax in C++20

With the release of C++20, the syntax for static assertions has been improved. You can now directly specify the condition without the need for a message:

static_assert(sizeof(int) == 4);

This simplifies the syntax and makes the code more readable.

Using concepts with static assertions

C++20 also introduces concepts, which are a powerful tool for expressing type requirements. You can now combine concepts with static assertions to enforce type constraints at compile time.

template <typename T>
concept Integral = std::is_integral<T>::value;

template <Integral T>
void processInteger(T value) {
  // ...
}

static_assert(Integral<int>, "int must be an integral type");

In the code above, the Integral concept is used to ensure that T is an integral type. The static_assert enforces this requirement at compile time.

Conclusion

Static assertions are an important feature in C++ for catching errors early in the development process. With the improved syntax in C++20 and the ability to use concepts, static assertions have become even more powerful and expressive.

References:

• C++20 Standard - https://isocpp.org/std/the-standard