# Extra Clang Tools 21.1.8 documentation

## clang-tidy - cppcoreguidelines-avoid-non-const-global-variables

# cppcoreguidelines-avoid-non-const-global-variables

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
    {
    public:
        char e = 0;
        const char f = 0;
    protected:
        char g = 0;
    private:
        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.

## Options

AllowInternalLinkage

  When set to true, static non-const variables and variables in anonymous namespaces will not generate a warning. The default value is false.