Finds non-const global variables as described in I.2 of C++ Core Guidelines <https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#Ri-global> . As R.6 of C++ Core Guidelines <https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#Rr-global> 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;

Variables: a, c, c_ptr1, c_ptr2, c_const_ptr and c_reference, will all generate warnings since they are either: a globally accessible variable and non-const, a pointer or reference providing global access to non-const data or both.