[BUG]: Docs bug fix/improvements for inherited overloaded virtual methods
deadlocklogic opened this issue · comments
deadlocklogic commented
Required prerequisites
- Make sure you've read the documentation. Your issue may be addressed there.
- Search the issue tracker and Discussions to verify that this hasn't already been reported. +1 or comment there if it has.
- Consider asking first in the Gitter chat room or in a Discussion.
What version (or hash if on master) of pybind11 are you using?
master
Problem description
Consider the documentation: Inheritance
If we add a virtual function overload, then the compilation fails.
class Animal {
public:
virtual std::string go() { return ""; } // Added virtual overload
virtual std::string go(int n_times) = 0;
virtual std::string name() { return "unknown"; }
};
class Dog : public Animal {
public:
std::string go(int n_times) override {
std::string result;
for (int i=0; i<n_times; ++i)
result += bark() + " ";
return result;
}
virtual std::string bark() { return "woof!"; }
};
template <class AnimalBase = Animal> class PyAnimal : public AnimalBase {
public:
using AnimalBase::AnimalBase; // Inherit constructors
std::string go() override { PYBIND11_OVERRIDE(std::string, AnimalBase, go, ); } // Added virtual overload
std::string go(int n_times) override { PYBIND11_OVERRIDE_PURE(std::string, AnimalBase, go, n_times); }
std::string name() override { PYBIND11_OVERRIDE(std::string, AnimalBase, name, ); }
};
template <class DogBase = Dog> class PyDog : public PyAnimal<DogBase> {
public:
using PyAnimal<DogBase>::PyAnimal; // Inherit constructors
// Override PyAnimal's pure virtual go() with a non-pure one:
std::string go(int n_times) override { PYBIND11_OVERRIDE(std::string, DogBase, go, n_times); }
std::string bark() override { PYBIND11_OVERRIDE(std::string, DogBase, bark, ); }
};
Now this won't compile!
So since we are registering every virtual method for each class we should explicitly use the base class like the following:
template <class AnimalBase = Animal> class PyAnimal : public AnimalBase {
public:
using AnimalBase::AnimalBase; // Inherit constructors
std::string go() override { PYBIND11_OVERRIDE(std::string, Animal, go, ); }
std::string go(int n_times) override { PYBIND11_OVERRIDE_PURE(std::string, Animal, go, n_times); }
std::string name() override { PYBIND11_OVERRIDE(std::string, Animal, name, ); }
};
template <class DogBase = Dog> class PyDog : public PyAnimal<DogBase> {
public:
using PyAnimal<DogBase>::PyAnimal; // Inherit constructors
// Override PyAnimal's pure virtual go() with a non-pure one:
std::string go(int n_times) override { PYBIND11_OVERRIDE(std::string, Dog, go, n_times); }
std::string bark() override { PYBIND11_OVERRIDE(std::string, Dog, bark, ); }
};
Now compilation succeeds.
Thanks.
Reproducible example code
No response
Is this a regression? Put the last known working version here if it is.
Not a regression
deadlocklogic commented
Now this is more verbose, because every inherited class needs to be explicitly registered but compilation succeeds.
If you don't want to use this fix, you can at least mention that the suggested trampoline technique doesn't work when there is hidden virtual overloaded methods.
Thanks.