c++ - Suppress delete-non-virtual-dtor warning when using a protected non-virtual destructor -

i have pure abstract interface class, , derived class implements interface.

struct foo {     virtual void dostuff() = 0; };  struct bar : foo {     void dostuff() override { } }; 

my interface class doesn't have virtual destructor.

attempting destruct derived instance using base class pointer therefore undefined behaviour

int main() {     foo* f = new bar;     f->dostuff();     delete f; } 

luckily compiler clever enough catch (with -werror)

main.cc:15:9: error: deleting object of abstract class type ‘foo’ has     non-virtual destructor cause undefined behaviour [-werror=delete-non-virtual-dtor]  delete f;         ^ 

i can avoid undefined behaviour ensuring don't attempt delete using base class pointer

int main() {     bar* b = new bar;     b->dostuff();     delete b; } 

unfortunately it's not clever enough pick program formed, , spits out similar error

main.cc:15:9: error: deleting object of polymorphic class type ‘bar’ has      non-virtual destructor might cause undefined behaviour [-werror=delete-non-virtual-dtor]   delete b;      ^ 

interestingly says might cause undefined behaviour, not will

protected non-virtual destructor:

in one of herb sutter's guru of week's gives following advice:

guideline #4: base class destructor should either public , virtual, or protected , nonvirtual.

so lets make destructor protected nonvirtual.

struct foo {     virtual void dostuff() = 0; protected:     ~foo() = default; };  struct bar : foo {     void dostuff() override { } }; 

now when accidentally try delete using base class pointer failure

int main() {     foo* f = new bar;     f->dostuff();     delete f; } 

main.cc:5:2: error: ‘foo::~foo()’ protected   ~foo() = default;   ^ main.cc:17:9: error: within context   delete f;          ^ 

great, gives me looking for. let's fix code don't delete using base class pointer

int main() {     bar* b = new bar;     b->dostuff();     delete b; } 

unfortunately same error before

main.cc:17:9: error: deleting object of polymorphic class type ‘bar’ has  non-virtual destructor might cause undefined behaviour [-werror=delete-non-virtual-dtor]   delete b;          ^ 

question:

how can best of both worlds?

• keep delete-non-virtual-dtor error when forget create protected non-virtual destructor, , try delete through base-class pointer
• suppress warning when use protected non-virtual destructor, , delete through derived-class pointer

super awesome bonus extra:

• suppress warning when forget use protected non-virtual destructor, correctly deleting through derived-class pointer

marking class final remove warning.

struct bar final : foo {     void dostuff() override { } };  int main() {     bar* f = new bar;     f->dostuff();     delete f; } 

demo