modernize-use-equals-delete

Identifies unimplemented private special member functions, and recommends using = delete for them. Additionally, it recommends relocating any deleted member function from the private to the public section.

Before the introduction of C++11, the primary method to effectively “erase” a particular function involved declaring it as private without providing a definition. This approach would result in either a compiler error (when attempting to call a private function) or a linker error (due to an undefined reference).

However, subsequent to the advent of C++11, a more conventional approach emerged for achieving this purpose. It involves flagging functions as = delete and keeping them in the public section of the class.

To prevent false positives, this check is only active within a translation unit where all other member functions have been implemented. The check will generate partial fixes by introducing = delete, but the user is responsible for manually relocating functions to the public section.

// Example: bad
class A {
 private:
  A(const A&);
  A& operator=(const A&);
};

// Example: good
class A {
 public:
  A(const A&) = delete;
  A& operator=(const A&) = delete;
};

IgnoreMacros

If this option is set to true (default is true), the check will not warn about functions declared inside macros.