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* fix: the types for return_value_policy_override in optional_caster `return_value_policy_override` was not being applied correctly in `optional_caster` in two ways: - The `is_lvalue_reference` condition referenced `T`, which was the `optional<T>` type parameter from the class, when it should have used `T_`, which was the parameter to the `cast` function. `T_` can potentially be a reference type, but `T` will never be. - The type parameter passed to `return_value_policy_override` should be `T::value_type`, not `T`. This matches the way that the other STL container type casters work. The result of these issues was that a method/property definition which used a `reference` or `reference_internal` return value policy would create a Python value that's bound by reference to a temporary C++ object, resulting in undefined behavior. For reasons that I was not able to figure out fully, it seems like this causes problems when using old versions of `boost::optional`, but not with recent versions of `boost::optional` or the `libstdc++` implementation of `std::optional`. The issue (that the override to `return_value_policy::move` is never being applied) is present for all implementations, it just seems like that somehow doesn't result in problems for the some implementation of `optional`. This change includes a regression type with a custom optional-like type which was able to reproduce the issue. Part of the issue with using the wrong types may have stemmed from the type variables `T` and `T_` having very similar names. This also changes the type variables in `optional_caster` to use slightly more descriptive names, which also more closely follow the naming convention used by the other STL casters. Fixes #3330 * Fix clang-tidy complaints * Add missing NOLINT * Apply a couple more fixes * fix: support GCC 4.8 * tests: avoid warning about unknown compiler for compilers missing C++17 * Remove unneeded test module attribute * Change test enum to have more unique int values Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com> Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com> |
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