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Removing rtti_held from smart_holder. See updated comment.

This commit is contained in:
Ralf W. Grosse-Kunstleve 2021-01-23 11:10:01 -08:00
parent 0f82a0b014
commit c30cc404c9
3 changed files with 48 additions and 63 deletions
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8
include/pybind11/detail/classh_type_casters.h
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@ -353,10 +353,10 @@ struct classh_type_caster : smart_holder_type_caster_load<T> {
// clang-format off
operator T() { return this->loaded_smhldr_ptr->template lvalue_ref<T>(); }
operator T&&() && { return this->loaded_smhldr_ptr->template rvalue_ref<T>(); }
operator T const&() { return this->loaded_smhldr_ptr->template lvalue_ref<T>(); }
operator T&() { return this->loaded_smhldr_ptr->template lvalue_ref<T>(); }
operator T() { return this->loaded_smhldr_ptr->template as_lvalue_ref<T>(); }
operator T&&() && { return this->loaded_smhldr_ptr->template as_rvalue_ref<T>(); }
operator T const&() { return this->loaded_smhldr_ptr->template as_lvalue_ref<T>(); }
operator T&() { return this->loaded_smhldr_ptr->template as_lvalue_ref<T>(); }
operator T const*() { return this->loaded_as_raw_ptr_unowned(); }
operator T*() { return this->loaded_as_raw_ptr_unowned(); }

69
include/pybind11/smart_holder_poc.h
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@ -12,7 +12,13 @@ High-level aspects:
C++ Undefined Behavior, especially from Python.
* Support a system design with clean runtime inheritance casting. From this
it follows that the `smart_holder` needs to be type-erased (`void*`, RTTI).
it follows that the `smart_holder` needs to be type-erased (`void*`).
* Handling of RTTI for the type-erased held pointer is NOT implemented here.
It is the responsibility of the caller to ensure that `static_cast<T *>`
is well-formed when calling `as_*` member functions. Inheritance casting
needs to be handled in a different layer (similar to the code organization
in boost/python/object/inheritance.hpp).
Details:
@ -28,10 +34,6 @@ Details:
* If created from an external `shared_ptr`, or a `unique_ptr` with a custom
deleter, including life-time management for external objects is infeasible.
* The `typename T` between `from` and `as` calls must match exactly.
Inheritance casting needs to be handled in a different layer (similar
to the code organization in boost/python/object/inheritance.hpp).
* The smart_holder is movable but not copyable, as a consequence of using
unique_ptr for the vptr_deleter_armed_flag_ptr. Note that the bool for
the flag has to live on the heap, for the smart_holder to be movable.
@ -72,35 +74,30 @@ struct guarded_custom_deleter {
};
struct smart_holder {
const std::type_info *rtti_held;
const std::type_info *rtti_uqp_del;
std::unique_ptr<bool> vptr_deleter_armed_flag_ptr;
std::shared_ptr<void> vptr;
bool vptr_is_using_noop_deleter : 1;
bool vptr_is_using_builtin_delete : 1;
bool vptr_is_external_shared_ptr : 1;
bool is_populated : 1;
smart_holder()
: rtti_held{nullptr}, rtti_uqp_del{nullptr}, vptr_is_using_noop_deleter{false},
vptr_is_using_builtin_delete{false}, vptr_is_external_shared_ptr{false} {}
: rtti_uqp_del{nullptr}, vptr_is_using_noop_deleter{false},
vptr_is_using_builtin_delete{false}, vptr_is_external_shared_ptr{false}, is_populated{
false} {}
explicit smart_holder(bool vptr_deleter_armed_flag)
: rtti_held{nullptr}, rtti_uqp_del{nullptr}, vptr_deleter_armed_flag_ptr{new bool{
vptr_deleter_armed_flag}},
: rtti_uqp_del{nullptr}, vptr_deleter_armed_flag_ptr{new bool{vptr_deleter_armed_flag}},
vptr_is_using_noop_deleter{false}, vptr_is_using_builtin_delete{false},
vptr_is_external_shared_ptr{false} {}
vptr_is_external_shared_ptr{false}, is_populated{false} {}
bool has_pointee() const { return vptr.get() != nullptr; }
template <typename T>
void ensure_compatible_rtti_held(const char *context) const {
if (!rtti_held) {
void ensure_is_populated(const char *context) const {
if (!is_populated) {
throw std::runtime_error(std::string("Unpopulated holder (") + context + ").");
}
const std::type_info *rtti_requested = &typeid(T);
if (!(*rtti_requested == *rtti_held)) {
throw std::runtime_error(std::string("Incompatible type (") + context + ").");
}
}
template <typename D>
@ -153,50 +150,47 @@ struct smart_holder {
template <typename T>
static smart_holder from_raw_ptr_unowned(T *raw_ptr) {
smart_holder hld(false);
hld.rtti_held = &typeid(T);
hld.vptr.reset(raw_ptr, guarded_builtin_delete<T>(hld.vptr_deleter_armed_flag_ptr.get()));
hld.vptr_is_using_noop_deleter = true;
hld.is_populated = true;
return hld;
}
template <typename T>
T *as_raw_ptr_unowned() const {
static const char *context = "as_raw_ptr_unowned";
ensure_compatible_rtti_held<T>(context);
return static_cast<T *>(vptr.get());
}
template <typename T>
T &lvalue_ref() const {
static const char *context = "lvalue_ref";
ensure_compatible_rtti_held<T>(context);
T &as_lvalue_ref() const {
static const char *context = "as_lvalue_ref";
ensure_is_populated(context);
ensure_has_pointee(context);
return *static_cast<T *>(vptr.get());
return *as_raw_ptr_unowned<T>();
}
template <typename T>
T &&rvalue_ref() const {
static const char *context = "rvalue_ref";
ensure_compatible_rtti_held<T>(context);
T &&as_rvalue_ref() const {
static const char *context = "as_rvalue_ref";
ensure_is_populated(context);
ensure_has_pointee(context);
return std::move(*static_cast<T *>(vptr.get()));
return std::move(*as_raw_ptr_unowned<T>());
}
template <typename T>
static smart_holder from_raw_ptr_take_ownership(T *raw_ptr) {
smart_holder hld(true);
hld.rtti_held = &typeid(T);
hld.vptr.reset(raw_ptr, guarded_builtin_delete<T>(hld.vptr_deleter_armed_flag_ptr.get()));
hld.vptr_is_using_builtin_delete = true;
hld.is_populated = true;
return hld;
}
template <typename T>
T *as_raw_ptr_release_ownership(const char *context = "as_raw_ptr_release_ownership") {
ensure_compatible_rtti_held<T>(context);
ensure_vptr_is_using_builtin_delete(context);
ensure_use_count_1(context);
T *raw_ptr = static_cast<T *>(vptr.get());
T *raw_ptr = as_raw_ptr_unowned<T>();
*vptr_deleter_armed_flag_ptr = false;
vptr.reset();
return raw_ptr;
@ -205,11 +199,11 @@ struct smart_holder {
template <typename T>
static smart_holder from_unique_ptr(std::unique_ptr<T> &&unq_ptr) {
smart_holder hld(true);
hld.rtti_held = &typeid(T);
hld.vptr.reset(unq_ptr.get(),
guarded_builtin_delete<T>(hld.vptr_deleter_armed_flag_ptr.get()));
unq_ptr.release();
hld.vptr_is_using_builtin_delete = true;
hld.is_populated = true;
return hld;
}
@ -221,21 +215,20 @@ struct smart_holder {
template <typename T, typename D>
static smart_holder from_unique_ptr_with_deleter(std::unique_ptr<T, D> &&unq_ptr) {
smart_holder hld(true);
hld.rtti_held = &typeid(T);
hld.rtti_uqp_del = &typeid(D);
hld.vptr.reset(unq_ptr.get(),
guarded_custom_deleter<T, D>(hld.vptr_deleter_armed_flag_ptr.get()));
unq_ptr.release();
hld.is_populated = true;
return hld;
}
template <typename T, typename D>
std::unique_ptr<T, D> as_unique_ptr_with_deleter() {
static const char *context = "as_unique_ptr_with_deleter";
ensure_compatible_rtti_held<T>(context);
ensure_compatible_rtti_uqp_del<D>(context);
ensure_use_count_1(context);
T *raw_ptr = static_cast<T *>(vptr.get());
T *raw_ptr = as_raw_ptr_unowned<T>();
*vptr_deleter_armed_flag_ptr = false;
vptr.reset();
return std::unique_ptr<T, D>(raw_ptr);
@ -244,16 +237,14 @@ struct smart_holder {
template <typename T>
static smart_holder from_shared_ptr(std::shared_ptr<T> shd_ptr) {
smart_holder hld;
hld.rtti_held = &typeid(T);
hld.vptr = std::static_pointer_cast<void>(shd_ptr);
hld.vptr_is_external_shared_ptr = true;
hld.is_populated = true;
return hld;
}
template <typename T>
std::shared_ptr<T> as_shared_ptr() const {
static const char *context = "as_shared_ptr";
ensure_compatible_rtti_held<T>(context);
return std::static_pointer_cast<T>(vptr);
}
};

34
tests/core/smart_holder_poc_test.cpp
View File

@ -32,17 +32,17 @@ TEST_CASE("from_raw_ptr_unowned+as_raw_ptr_unowned", "[S]") {
REQUIRE(*hld.as_raw_ptr_unowned<int>() == 19);
}
TEST_CASE("from_raw_ptr_unowned+lvalue_ref", "[S]") {
TEST_CASE("from_raw_ptr_unowned+as_lvalue_ref", "[S]") {
static int value = 19;
auto hld = smart_holder::from_raw_ptr_unowned(&value);
REQUIRE(hld.lvalue_ref<int>() == 19);
REQUIRE(hld.as_lvalue_ref<int>() == 19);
}
TEST_CASE("from_raw_ptr_unowned+rvalue_ref", "[S]") {
TEST_CASE("from_raw_ptr_unowned+as_rvalue_ref", "[S]") {
helpers::movable_int orig(19);
{
auto hld = smart_holder::from_raw_ptr_unowned(&orig);
helpers::movable_int othr(hld.rvalue_ref<helpers::movable_int>());
helpers::movable_int othr(hld.as_rvalue_ref<helpers::movable_int>());
REQUIRE(othr.valu == 19);
REQUIRE(orig.valu == 91);
}
@ -78,10 +78,10 @@ TEST_CASE("from_raw_ptr_unowned+as_shared_ptr", "[S]") {
REQUIRE(*hld.as_shared_ptr<int>() == 19);
}
TEST_CASE("from_raw_ptr_take_ownership+lvalue_ref", "[S]") {
TEST_CASE("from_raw_ptr_take_ownership+as_lvalue_ref", "[S]") {
auto hld = smart_holder::from_raw_ptr_take_ownership(new int(19));
REQUIRE(hld.has_pointee());
REQUIRE(hld.lvalue_ref<int>() == 19);
REQUIRE(hld.as_lvalue_ref<int>() == 19);
}
TEST_CASE("from_raw_ptr_take_ownership+as_raw_ptr_release_ownership1", "[S]") {
@ -127,11 +127,11 @@ TEST_CASE("from_raw_ptr_take_ownership+as_shared_ptr", "[S]") {
REQUIRE(*new_owner == 19);
}
TEST_CASE("from_unique_ptr+lvalue_ref", "[S]") {
TEST_CASE("from_unique_ptr+as_lvalue_ref", "[S]") {
std::unique_ptr<int> orig_owner(new int(19));
auto hld = smart_holder::from_unique_ptr(std::move(orig_owner));
REQUIRE(orig_owner.get() == nullptr);
REQUIRE(hld.lvalue_ref<int>() == 19);
REQUIRE(hld.as_lvalue_ref<int>() == 19);
}
TEST_CASE("from_unique_ptr+as_raw_ptr_release_ownership1", "[S]") {
@ -189,11 +189,11 @@ TEST_CASE("from_unique_ptr+as_shared_ptr", "[S]") {
REQUIRE(*new_owner == 19);
}
TEST_CASE("from_unique_ptr_with_deleter+lvalue_ref", "[S]") {
TEST_CASE("from_unique_ptr_with_deleter+as_lvalue_ref", "[S]") {
std::unique_ptr<int, helpers::functor_builtin_delete<int>> orig_owner(new int(19));
auto hld = smart_holder::from_unique_ptr_with_deleter(std::move(orig_owner));
REQUIRE(orig_owner.get() == nullptr);
REQUIRE(hld.lvalue_ref<int>() == 19);
REQUIRE(hld.as_lvalue_ref<int>() == 19);
}
TEST_CASE("from_unique_ptr_with_deleter+as_raw_ptr_release_ownership", "[E]") {
@ -241,10 +241,10 @@ TEST_CASE("from_unique_ptr_with_deleter+as_shared_ptr", "[S]") {
REQUIRE(*new_owner == 19);
}
TEST_CASE("from_shared_ptr+lvalue_ref", "[S]") {
TEST_CASE("from_shared_ptr+as_lvalue_ref", "[S]") {
std::shared_ptr<int> orig_owner(new int(19));
auto hld = smart_holder::from_shared_ptr(orig_owner);
REQUIRE(hld.lvalue_ref<int>() == 19);
REQUIRE(hld.as_lvalue_ref<int>() == 19);
}
TEST_CASE("from_shared_ptr+as_raw_ptr_release_ownership", "[E]") {
@ -279,19 +279,13 @@ TEST_CASE("from_shared_ptr+as_shared_ptr", "[S]") {
TEST_CASE("error_unpopulated_holder", "[E]") {
smart_holder hld;
REQUIRE_THROWS_WITH(hld.as_raw_ptr_unowned<int>(), "Unpopulated holder (as_raw_ptr_unowned).");
}
TEST_CASE("error_incompatible_type", "[E]") {
static int value = 19;
auto hld = smart_holder::from_raw_ptr_unowned(&value);
REQUIRE_THROWS_WITH(hld.as_unique_ptr<std::string>(), "Incompatible type (as_unique_ptr).");
REQUIRE_THROWS_WITH(hld.as_lvalue_ref<int>(), "Unpopulated holder (as_lvalue_ref).");
}
TEST_CASE("error_disowned_holder", "[E]") {
auto hld = smart_holder::from_raw_ptr_take_ownership(new int(19));
hld.as_unique_ptr<int>();
REQUIRE_THROWS_WITH(hld.lvalue_ref<int>(), "Disowned holder (lvalue_ref).");
REQUIRE_THROWS_WITH(hld.as_lvalue_ref<int>(), "Disowned holder (as_lvalue_ref).");
}
TEST_CASE("error_cannot_disown_nullptr", "[E]") {