Modern C++ Programming Cookbook

How to do it...

Use static_assert declarations to ensure that conditions in different scopes are met:

• namespace: In this example, we validate that the size of the class item is always 16:

        struct alignas(8) item         {           int      id;           bool     active;           double   value;         };         static_assert(sizeof(item) == 16,                        "size of item must be 16 bytes");

• class: In this example, we validate that pod_wrapper can only be used with POD types:

        template <typename T>         class pod_wrapper         {           static_assert(std::is_pod<T>::value,                          "POD type expected!");           T value;         };         struct point         {           int x;           int y;         };         pod_wrapper<int>         w1; // OK         pod_wrapper<point>       w2; // OK         pod_wrapper<std::string> w3; // error: POD type expected

• block (function): In this example, we validate that a ...