[BUG]: Docs bug fix/improvements for inherited overloaded virtual methods
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Description
Required prerequisites
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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
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start at the Inheritance section, “Combining virtual functions and inheritance,” linked in the issue. Compare the overloaded virtual-method example with the corrected version, update the documented override macros to use the appropriate base classes, and verify that the example compiles.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp
- Domain
- documentation
- Issue type
- Documentation
- Difficulty
- 2/5
- Estimated time
- 1-3 hours
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 50/100