From 898794488a23c6d51b3474814939a60e5f68a096 Mon Sep 17 00:00:00 2001 From: Xiaofei Wang <6218006+wangxf123456@users.noreply.github.com> Date: Sat, 10 Aug 2024 04:28:12 +0800 Subject: [PATCH] Add `type_caster_std_function_specializations` feature. (#4597) * Allow specializations based on callback function return values. * clang-tidy auto fix * Add a test case for function specialization. * Add test for callback function that raises Python exception. * Fix test failures. * style: pre-commit fixes * Add `#define PYBIND11_HAS_TYPE_CASTER_STD_FUNCTION_SPECIALIZATIONS` --------- Co-authored-by: Ralf W. Grosse-Kunstleve Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com> --- include/pybind11/functional.h | 79 +++++++++++-------- tests/CMakeLists.txt | 1 + ...pe_caster_std_function_specializations.cpp | 46 +++++++++++ ...ype_caster_std_function_specializations.py | 15 ++++ 4 files changed, 107 insertions(+), 34 deletions(-) create mode 100644 tests/test_type_caster_std_function_specializations.cpp create mode 100644 tests/test_type_caster_std_function_specializations.py diff --git a/include/pybind11/functional.h b/include/pybind11/functional.h index 6856119cd..4b3610117 100644 --- a/include/pybind11/functional.h +++ b/include/pybind11/functional.h @@ -9,12 +9,55 @@ #pragma once +#define PYBIND11_HAS_TYPE_CASTER_STD_FUNCTION_SPECIALIZATIONS + #include "pybind11.h" #include PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE) PYBIND11_NAMESPACE_BEGIN(detail) +PYBIND11_NAMESPACE_BEGIN(type_caster_std_function_specializations) + +// ensure GIL is held during functor destruction +struct func_handle { + function f; +#if !(defined(_MSC_VER) && _MSC_VER == 1916 && defined(PYBIND11_CPP17)) + // This triggers a syntax error under very special conditions (very weird indeed). + explicit +#endif + func_handle(function &&f_) noexcept + : f(std::move(f_)) { + } + func_handle(const func_handle &f_) { operator=(f_); } + func_handle &operator=(const func_handle &f_) { + gil_scoped_acquire acq; + f = f_.f; + return *this; + } + ~func_handle() { + gil_scoped_acquire acq; + function kill_f(std::move(f)); + } +}; + +// to emulate 'move initialization capture' in C++11 +struct func_wrapper_base { + func_handle hfunc; + explicit func_wrapper_base(func_handle &&hf) noexcept : hfunc(hf) {} +}; + +template +struct func_wrapper : func_wrapper_base { + using func_wrapper_base::func_wrapper_base; + Return operator()(Args... args) const { + gil_scoped_acquire acq; + // casts the returned object as a rvalue to the return type + return hfunc.f(std::forward(args)...).template cast(); + } +}; + +PYBIND11_NAMESPACE_END(type_caster_std_function_specializations) template struct type_caster> { @@ -77,40 +120,8 @@ public: // See PR #1413 for full details } - // ensure GIL is held during functor destruction - struct func_handle { - function f; -#if !(defined(_MSC_VER) && _MSC_VER == 1916 && defined(PYBIND11_CPP17)) - // This triggers a syntax error under very special conditions (very weird indeed). - explicit -#endif - func_handle(function &&f_) noexcept - : f(std::move(f_)) { - } - func_handle(const func_handle &f_) { operator=(f_); } - func_handle &operator=(const func_handle &f_) { - gil_scoped_acquire acq; - f = f_.f; - return *this; - } - ~func_handle() { - gil_scoped_acquire acq; - function kill_f(std::move(f)); - } - }; - - // to emulate 'move initialization capture' in C++11 - struct func_wrapper { - func_handle hfunc; - explicit func_wrapper(func_handle &&hf) noexcept : hfunc(std::move(hf)) {} - Return operator()(Args... args) const { - gil_scoped_acquire acq; - // casts the returned object as a rvalue to the return type - return hfunc.f(std::forward(args)...).template cast(); - } - }; - - value = func_wrapper(func_handle(std::move(func))); + value = type_caster_std_function_specializations::func_wrapper( + type_caster_std_function_specializations::func_handle(std::move(func))); return true; } diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt index aae9be720..5b7e3f801 100644 --- a/tests/CMakeLists.txt +++ b/tests/CMakeLists.txt @@ -158,6 +158,7 @@ set(PYBIND11_TEST_FILES test_tagbased_polymorphic test_thread test_type_caster_pyobject_ptr + test_type_caster_std_function_specializations test_union test_unnamed_namespace_a test_unnamed_namespace_b diff --git a/tests/test_type_caster_std_function_specializations.cpp b/tests/test_type_caster_std_function_specializations.cpp new file mode 100644 index 000000000..89213ddb1 --- /dev/null +++ b/tests/test_type_caster_std_function_specializations.cpp @@ -0,0 +1,46 @@ +#include +#include + +#include "pybind11_tests.h" + +namespace py = pybind11; + +namespace { + +struct SpecialReturn { + int value = 99; +}; + +} // namespace + +namespace pybind11 { +namespace detail { +namespace type_caster_std_function_specializations { + +template +struct func_wrapper : func_wrapper_base { + using func_wrapper_base::func_wrapper_base; + SpecialReturn operator()(Args... args) const { + gil_scoped_acquire acq; + SpecialReturn result; + try { + result = hfunc.f(std::forward(args)...).template cast(); + } catch (error_already_set &) { + result.value += 1; + } + result.value += 100; + return result; + } +}; + +} // namespace type_caster_std_function_specializations +} // namespace detail +} // namespace pybind11 + +TEST_SUBMODULE(type_caster_std_function_specializations, m) { + py::class_(m, "SpecialReturn") + .def(py::init<>()) + .def_readwrite("value", &SpecialReturn::value); + m.def("call_callback_with_special_return", + [](const std::function &func) { return func(); }); +} diff --git a/tests/test_type_caster_std_function_specializations.py b/tests/test_type_caster_std_function_specializations.py new file mode 100644 index 000000000..9e45d4f59 --- /dev/null +++ b/tests/test_type_caster_std_function_specializations.py @@ -0,0 +1,15 @@ +from __future__ import annotations + +from pybind11_tests import type_caster_std_function_specializations as m + + +def test_callback_with_special_return(): + def return_special(): + return m.SpecialReturn() + + def raise_exception(): + raise ValueError("called raise_exception.") + + assert return_special().value == 99 + assert m.call_callback_with_special_return(return_special).value == 199 + assert m.call_callback_with_special_return(raise_exception).value == 200