Jason Rhinelander 2097826346 Fix template trampoline overload lookup failure ... Problem ======= The template trampoline pattern documented in PR #322 has a problem with virtual method overloads in intermediate classes in the inheritance chain between the trampoline class and the base class. For example, consider the following inheritance structure, where `B` is the actual class, `PyB<B>` is the trampoline class, and `PyA<B>` is an intermediate class adding A's methods into the trampoline: PyB<B> -> PyA<B> -> B -> A Suppose PyA<B> has a method `some_method()` with a PYBIND11_OVERLOAD in it to overload the virtual `A::some_method()`. If a Python class `C` is defined that inherits from the pybind11-registered `B` and tries to provide an overriding `some_method()`, the PYBIND11_OVERLOADs declared in PyA<B> fails to find this overloaded method, and thus never invoke it (or, if pure virtual and not overridden in PyB<B>, raises an exception). This happens because the base (internal) `PYBIND11_OVERLOAD_INT` macro simply calls `get_overload(this, name)`; `get_overload()` then uses the inferred type of `this` to do a type lookup in `registered_types_cpp`. This is where it fails: `this` will be a `PyA<B> *`, but `PyA<B>` is neither the base type (`B`) nor the trampoline type (`PyB<B>`). As a result, the overload fails and we get a failed overload lookup. The fix ======= The fix is relatively simple: we can cast `this` passed to `get_overload()` to a `const B *`, which lets get_overload look up the correct class. Since trampoline classes should be derived from `B` classes anyway, this cast should be perfectly safe. This does require adding the class name as an argument to the PYBIND11_OVERLOAD_INT macro, but leaves the public macro signatures unchanged.		2016-08-29 19:41:44 -04:00
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pybind11	Fix template trampoline overload lookup failure	2016-08-29 19:41:44 -04:00