Overriding a [[noreturn]] virtual function

Question

The [[noreturn]] attribute can be applied to functions that are not meant to return. For example:

[[noreturn]] void will_throw() { throw std::runtime_error("bad, bad, bad ...."); } 

But I've encountered the following situation (no, I didn't design this):

class B { public:   virtual void f() { throw std::runtime_error(""); } };  class D : public B {   void f() override { std::cout << "Hi" << std::endl; } }; 

I would really like to place the attribute [[noreturn]] on the B::f() declaration. But I'm unclear as to what happens to the override in the derived class. Successfully returning from a [[noreturn]] function results in undefined behavior, and I certainly don't want that if an override also inherits the attribute.

The question: By overriding [[noreturn] virtual void B::f(), do I inherit the [[noreturn]] attribute?

I've looked through the C++14 standard, and I'm having trouble determining if attributes are inherited.

Answer 1

I have grepped through the standard, and there's no indication that either [[noreturn]] specifically, or attributes more generally, are "inherited" by overriding functions.

It's hard to prove a negative, and the standard actually doesn't declare this either way but, since A::f() and B::f() are still distinct functions and the only behaviour described is defined in terms of functions, I think you're safe to mark A::f() as [[noreturn]].

That being said, I can't imagine what useful optimisation the compiler could subsequently perform, given the dynamic dispatch.

Answer 2

In practice, neither g++, clang nor MSVC consider the [[noreturn]] attribute as inherited

#include <iostream>  struct B { public:   [[noreturn]] virtual void f() { std::cout << "B\n"; throw 0; } };  struct D : public B {   void f() override { std::cout << "D\n"; } };  int main()  {     try { B{}.f(); } catch(...) {}     D{}.f();      B* d = new D{};     d->f(); } 

which prints out "B", "D" and "D" for all three compilers.