[smart_holder] Bug fix: `std::unique_ptr` deleter needs to be copied. (#4850)
* Store `std::function<void (void *)>` del_fun; in `guarded_delete`
* Specialize the simple common case.
Using a `union` is complicated: https://en.cppreference.com/w/cpp/language/union
> If members of a union are classes with user-defined constructors and destructors, to switch the active member, explicit destructor and placement new are generally needed:
Using `std::variant` increases compile-time overhead.
It is currently unclear how much these effects matter in practice: optimization left for later.
* Add one test case (more later).
* Add `const` to resolve clang-tidy error.
```
-- The CXX compiler identification is Clang 15.0.7
/usr/bin/cmake -E __run_co_compile --tidy="/usr/bin/clang-tidy;--use-color;--warnings-as-errors=*;--extra-arg-before=--driver-mode=g++" --source=/__w/pybind11/pybind11/tests/test_class_sh_inheritance.cpp -- /usr/bin/c++ -DPYBIND11_ENABLE_TYPE_CASTER_ODR_GUARD_IF_AVAILABLE -DPYBIND11_TEST_EIGEN -Dpybind11_tests_EXPORTS -I/__w/pybind11/pybind11/include -isystem /usr/include/python3.9 -isystem /__w/pybind11/pybind11/build/_deps/eigen-src -Os -DNDEBUG -fPIC -fvisibility=hidden -Wall -Wextra -Wconversion -Wcast-qual -Wdeprecated -Wundef -Wnon-virtual-dtor -flto=thin -std=c++17 -o CMakeFiles/pybind11_tests.dir/test_class_sh_inheritance.cpp.o -c /__w/pybind11/pybind11/tests/test_class_sh_inheritance.cpp
/__w/pybind11/pybind11/tests/pure_cpp/smart_holder_poc_test.cpp:264:30: error: pointer parameter 'raw_ptr' can be pointer to const [readability-non-const-parameter,-warnings-as-errors]
new int(19), [](int *raw_ptr) { delete raw_ptr; });
^
const
```
* Introduce `struct custom_deleter` to ensure the deleter is moved as desired (the lambda function only captures a reference, which can become dangling).
* Resolve helpful clang-tidy errors.
```
/usr/bin/cmake -E __run_co_compile --tidy="/usr/bin/clang-tidy;--use-color;--warnings-as-errors=*;--extra-arg-before=--driver-mode=g++" --source=/__w/pybind11/pybind11/tests/test_class.cpp -- /usr/bin/c++ -DPYBIND11_ENABLE_TYPE_CASTER_ODR_GUARD_IF_AVAILABLE -DPYBIND11_TEST_EIGEN -Dpybind11_tests_EXPORTS -I/__w/pybind11/pybind11/include -isystem /usr/include/python3.9 -isystem /__w/pybind11/pybind11/build/_deps/eigen-src -Os -DNDEBUG -fPIC -fvisibility=hidden -Wall -Wextra -Wconversion -Wcast-qual -Wdeprecated -Wundef -Wnon-virtual-dtor -flto=thin -std=c++17 -o CMakeFiles/pybind11_tests.dir/test_class.cpp.o -c /__w/pybind11/pybind11/tests/test_class.cpp
/__w/pybind11/pybind11/include/pybind11/detail/smart_holder_poc.h:114:5: error: single-argument constructors must be marked explicit to avoid unintentional implicit conversions [google-explicit-constructor,-warnings-as-errors]
custom_deleter(D &&deleter) : deleter{std::move(deleter)} {}
^
explicit
/__w/pybind11/pybind11/include/pybind11/detail/smart_holder_poc.h:120:76: error: forwarding reference passed to std::move(), which may unexpectedly cause lvalues to be moved; use std::forward() instead [bugprone-move-forwarding-reference,-warnings-as-errors]
return guarded_delete(std::function<void(void *)>(custom_deleter<T, D>(std::move(uqp_del))),
^~~~~~~~~
std::forward<D>
```
* Workaround for gcc 4.8.5, clang 3.6
* Transfer reduced test here.
Reduced from a PyCLIF use case in the wild by @wangxf123456 (internal change cl/565476030).
* Add missing include (clangd Include Cleaner)
* Change `std::move` to `std::forward` as suggested by @iwanders.
* Add missing includes (clangd Include Cleaner)
* Use new `PYBIND11_TESTS_PURE_CPP_SMART_HOLDER_POC_TEST_CPP` to exclude `smart_holder::as_unique_ptr` method from production code.
* Systematically add `PYBIND11_TESTS_PURE_CPP_SMART_HOLDER_POC_TEST_CPP` to mark code that is not used from production code. Add comment to explain.
* Very simple experiment related to https://github.com/pybind/pybind11/pull/4850#issuecomment-1789780676
Does the `PYBIND11_TESTS_PURE_CPP_SMART_HOLDER_POC_TEST_CPP` define have anything to do with it?
* Revert "Very simple experiment related to https://github.com/pybind/pybind11/pull/4850#issuecomment-1789780676"
This reverts commit fe59369f408d354edef16e3d40e2f90d9c2a9ba8.
2023-11-02 15:21:13 +00:00
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from pybind11_tests import class_sh_unique_ptr_custom_deleter as m
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