Finds non-const global variables as described in I.2 of C++ Core Guidelines. As R.6 of C++ Core Guidelines is a duplicate of rule I.2 it also covers that rule.

char a;  // Warns!
const char b =  0;

namespace some_namespace
    char c;  // Warns!
    const char d = 0;

char * c_ptr1 = &some_namespace::c;  // Warns!
char *const c_const_ptr = &some_namespace::c;  // Warns!
char & c_reference = some_namespace::c;  // Warns!

class Foo  // No Warnings inside Foo, only namespace scope is covered
    char e = 0;
    const char f = 0;
    char g = 0;
    char h = 0;

The variables a, c, c_ptr1, c_const_ptr and c_reference will all generate warnings since they are either a non-const globally accessible variable, a pointer or a reference providing global access to non-const data or both.