Test:

class DB {
        protected:
        void foo() {};
};
class DC : public DB {
        public:
        DC() {
                [this]() {
                        DB::foo(); // #1
                }();
        };
};

int main(void)
{
        DC x;
}

This is potentially a duplicate of
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58972

Clang accepts the code. gcc prints

lambda-protected.cpp: In lambda function:
lambda-protected.cpp:3:14: error: ‘void DB::foo()’ is protected
         void foo() {};
              ^
lambda-protected.cpp:9:33: error: within this context
                         DB::foo();
                                 ^

And changing #1 to this->DB::foo(); does not help.