If you use a tiny subset of C++, then you get a dialect of C with more type safety, namespaces, mostly-not-unsafe subtype polymorphism through class inheritance

If you use a tiny subset of C++, then you get a dialect of C with more type safety, namespaces, mostly-not-unsafe subtype polymorphism through class inheritance, and also okay parametric polymorphism through templates. That dialect will compile a bit slower (it's still C++ after all), but produce code which either has the same performance as C or is only slightly behind C.