Preventing accidental public access in C++ structs

Default Access Specifiers in C++

In C++, struct and class differ primarily in their default access levels. Members of a struct are public by default, while members of a class are private. In large-scale projects, developers may interchangeably use these keywords without explicitly defining access specifiers, potentially exposing internal data members to external modification.

While static analysis tools like clang-tidy can identify redundant specifiers, there is no native compiler warning to alert a developer when a struct is used without an explicit private: or protected: label, increasing the risk of unintentional interface exposure.

What is the most reliable method for enforcing explicit access labels across a codebase to prevent accidental public exposure in struct definitions? Does any standard compiler flag provide a warning for missing access specifiers in types intended for encapsulation?