1 Commits

Author	SHA1	Message	Date
Noah Oblath	74b5242713	feat: add py::potentially_slicing_weak_ptr(handle) function (#5624) ... * Added weak_ptr test (currently failing) * Cleanup * [skip ci] Simplify test case. * Add test_class_sp_trampoline_weak_ptr.cpp,py (using std::shared_ptr as holder). Tweak test_class_sh_trampoline_weak_ptr.py to pass, with `# THIS NEEDS FIXING` comment. * Resolve clang-tidy errors ``` /__w/pybind11/pybind11/tests/test_class_sh_trampoline_weak_ptr.cpp:23:43: error: the parameter 'sp' is copied for each invocation but only used as a const reference; consider making it a const reference [performance-unnecessary-value-param,-warnings-as-errors] 23 | void set_wp(std::shared_ptr<VirtBase> sp) { wp = sp; } | ^ | const & 4443 warnings generated. ``` ``` /__w/pybind11/pybind11/tests/test_class_sp_trampoline_weak_ptr.cpp:23:43: error: the parameter 'sp' is copied for each invocation but only used as a const reference; consider making it a const reference [performance-unnecessary-value-param,-warnings-as-errors] 23 | void set_wp(std::shared_ptr<VirtBase> sp) { wp = sp; } | ^ | const & 4430 warnings generated. ``` * PYPY, GRAALPY: skip last part of test_weak_ptr_base * Rename test_weak_ptr_base → test_weak_ptr_owner * Add SpOwner, test_with_sp_owner, test_with_sp_and_wp_owners * Modify py::trampoline_self_life_support semantics: if trampoline class does not inherit from this class, preserve established Inheritance Slicing behavior. rwgk reached this point with the help of ChatGPT: * https://chatgpt.com/share/68056498-7d94-8008-8ff0-232e2aba451c The only production code change in this commit is: ``` diff --git a/include/pybind11/detail/type_caster_base.h b/include/pybind11/detail/type_caster_base.h index d4f9a41e..f3d45301 100644 --- a/include/pybind11/detail/type_caster_base.h +++ b/include/pybind11/detail/type_caster_base.h @@ -776,6 +776,14 @@ struct load_helper : value_and_holder_helper { if (released_ptr) { return std::shared_ptr<T>(released_ptr, type_raw_ptr); } + auto *self_life_support + = dynamic_raw_ptr_cast_if_possible<trampoline_self_life_support>(type_raw_ptr); + if (self_life_support == nullptr) { + std::shared_ptr<void> void_shd_ptr = hld.template as_shared_ptr<void>(); + std::shared_ptr<T> to_be_released(void_shd_ptr, type_raw_ptr); + vptr_gd_ptr->released_ptr = to_be_released; + return to_be_released; + } std::shared_ptr<T> to_be_released( type_raw_ptr, shared_ptr_trampoline_self_life_support(loaded_v_h.inst)); vptr_gd_ptr->released_ptr = to_be_released; ``` * Remove debug printf in include/pybind11/pybind11.h * Resolve MSVC error ``` 11>D:\a\pybind11\pybind11\tests\test_class_sp_trampoline_weak_ptr.cpp(44,50): error C2220: the following warning is treated as an error [D:\a\pybind11\pybind11\build\tests\pybind11_tests.vcxproj] 11>D:\a\pybind11\pybind11\tests\test_class_sp_trampoline_weak_ptr.cpp(44,50): warning C4458: declaration of 'sp' hides class member [D:\a\pybind11\pybind11\build\tests\pybind11_tests.vcxproj] D:\a\pybind11\pybind11\tests\test_class_sp_trampoline_weak_ptr.cpp(54,31): see declaration of 'pybind11_tests::class_sp_trampoline_weak_ptr::SpOwner::sp' ``` * [skip ci] Undo the production code change under 4638e017b6 Also undo the corresponding test change in test_class_sh_trampoline_weak_ptr.py But keep all extra debugging code for now. * [skip ci] Introduce lambda in `WpOwner::set_wp` bindings, but simply cast to `std::shared_ptr<VirtBase>` for now. * Add `py::potentially_slicing_shared_ptr()` * Add `type_id<T>()` to `py::potentially_slicing_shared_ptr()` error message and add test. * test_potentially_slicing_shared_ptr.cpp,py (for smart_holder only) * Generalize test_potentially_slicing_shared_ptr.cpp,py for testing with smart_holder and std::shared_ptr as holder. * Add back test_potentially_slicing_shared_ptr_not_convertible_error(), it got lost accidentally in commit 56d23dc478 * Add simple trampoline state assertions. * Resolve clang-tidy errors. ``` /__w/pybind11/pybind11/tests/test_potentially_slicing_shared_ptr.cpp:30:9: error: 'magic_token' should be initialized in a member initializer of the constructor [cppcoreguidelines-prefer-member-initializer,-warnings-as-errors] 29 | trampoline_is_alive_simple(const trampoline_is_alive_simple &other) { | : magic_token(other.magic_token) 30 | magic_token = other.magic_token; | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ /__w/pybind11/pybind11/tests/test_potentially_slicing_shared_ptr.cpp:33:9: error: 'magic_token' should be initialized in a member initializer of the constructor [cppcoreguidelines-prefer-member-initializer,-warnings-as-errors] 32 | trampoline_is_alive_simple(trampoline_is_alive_simple &&other) noexcept { | : magic_token(other.magic_token) 33 | magic_token = other.magic_token; | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ``` * Add a (long) C++ comment for py::potentially_slicing_shared_ptr<>() * [skip ci] Add new "Avoiding Inheritance Slicing and ``std::weak_ptr`` surprises" section in advanced/classes.rst * [skip ci] Add introductory comment to test_potentially_slicing_shared_ptr.py * Minimal (!) changes to have py::potentially_slicing_weak_ptr<T>(handle) as the public API. For CI testing, before changing the names around more widely, and the documentation. * Rename test_potentially_slicing_shared_ptr.cpp,py → test_potentially_slicing_weak_ptr.cpp,py * Update docs/advanced/classes.rst and C++ comments → potentially_slicing_weak_ptr * Write "shared_ptr" instead of just "pointer" in a couple places in docs/advanced/classes.rst * Add comment for force_potentially_slicing_shared_ptr in type_caster_base.h, to make a direct connection py::potentially_slicing_weak_ptr --------- Co-authored-by: Ralf W. Grosse-Kunstleve <rgrossekunst@nvidia.com>	2025-05-13 10:07:33 -04:00