Adding from_shared_ptr. Some polishing.

include/pybind11/smart_holder_poc.h

@@ -3,12 +3,14 @@
 #include <memory>
 #include <typeinfo>
 
-PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+namespace pybindit {
+namespace memory {
 
 template <typename T>
 struct guarded_builtin_delete {
   bool* flag_ptr;
-  explicit guarded_builtin_delete(bool* flag_ptr_) : flag_ptr{flag_ptr_} {}
+  explicit guarded_builtin_delete(bool* guard_flag_ptr)
+      : flag_ptr{guard_flag_ptr} {}
   void operator()(T* raw_ptr) {
     if (*flag_ptr) delete raw_ptr;
   }
@@ -17,27 +19,30 @@ struct guarded_builtin_delete {
 template <typename T, typename D>
 struct guarded_custom_deleter {
   bool* flag_ptr;
-  explicit guarded_custom_deleter(bool* flag_ptr_) : flag_ptr{flag_ptr_} {}
+  explicit guarded_custom_deleter(bool* guard_flag_ptr)
+      : flag_ptr{guard_flag_ptr} {}
   void operator()(T* raw_ptr) {
     if (*flag_ptr) D()(raw_ptr);
   }
 };
 
 struct smart_holder {
-  std::shared_ptr<void> vptr;
   const std::type_info* rtti_held;
   const std::type_info* rtti_uqp_del;
-  bool vptr_deleter_flag;
+  std::shared_ptr<void> vptr;
+  bool vptr_deleter_guard_flag;
 
   void clear() {
     vptr.reset();
-    vptr_deleter_flag = false;
+    vptr_deleter_guard_flag = false;
     rtti_held = nullptr;
     rtti_uqp_del = nullptr;
   }
 
   smart_holder()
-      : rtti_held{nullptr}, rtti_uqp_del{nullptr}, vptr_deleter_flag{false} {}
+      : rtti_held{nullptr},
+        rtti_uqp_del{nullptr},
+        vptr_deleter_guard_flag{false} {}
 
   template <typename T>
   void ensure_compatible_rtti_held(const char* context) {
@@ -57,7 +62,7 @@ struct smart_holder {
     }
   }
 
-  void ensure_vptr_deleter_flag_true(const char* context) {
+  void ensure_vptr_deleter_guard_flag_true(const char* context) {
     if (rtti_uqp_del != nullptr) {
       throw std::runtime_error(std::string("Cannot disown this shared_ptr (") +
                                context + ").");
@@ -71,36 +76,29 @@ struct smart_holder {
     }
   }
 
-  template <typename T>
-  std::shared_ptr<T> as_shared_ptr() {
-    static const char* context = "as_shared_ptr";
-    ensure_compatible_rtti_held<T>(context);
-    return std::static_pointer_cast<T>(vptr);
-  }
-
   template <typename T>
   void from_raw_ptr_owned(T* raw_ptr) {
     clear();
     rtti_held = &typeid(T);
-    vptr_deleter_flag = true;
-    vptr.reset(raw_ptr, guarded_builtin_delete<T>(&vptr_deleter_flag));
+    vptr_deleter_guard_flag = true;
+    vptr.reset(raw_ptr, guarded_builtin_delete<T>(&vptr_deleter_guard_flag));
   }
 
   template <typename T>
   void from_raw_ptr_unowned(T* raw_ptr) {
     clear();
     rtti_held = &typeid(T);
-    vptr_deleter_flag = false;
-    vptr.reset(raw_ptr, guarded_builtin_delete<T>(&vptr_deleter_flag));
+    vptr_deleter_guard_flag = false;
+    vptr.reset(raw_ptr, guarded_builtin_delete<T>(&vptr_deleter_guard_flag));
   }
 
   template <typename T>
   T* as_raw_ptr_owned(const char* context = "as_raw_ptr_owned") {
     ensure_compatible_rtti_held<T>(context);
-    ensure_vptr_deleter_flag_true(context);
+    ensure_vptr_deleter_guard_flag_true(context);
     ensure_use_count_1(context);
     T* raw_ptr = static_cast<T*>(vptr.get());
-    vptr_deleter_flag = false;
+    vptr_deleter_guard_flag = false;
     vptr.reset();
     return raw_ptr;
   }
@@ -116,8 +114,9 @@ struct smart_holder {
   void from_unique_ptr(std::unique_ptr<T>&& unq_ptr) {
     clear();
     rtti_held = &typeid(T);
-    vptr_deleter_flag = true;
-    vptr.reset(unq_ptr.get(), guarded_builtin_delete<T>(&vptr_deleter_flag));
+    vptr_deleter_guard_flag = true;
+    vptr.reset(unq_ptr.get(),
+               guarded_builtin_delete<T>(&vptr_deleter_guard_flag));
     unq_ptr.release();
   }
 
@@ -131,8 +130,9 @@ struct smart_holder {
     clear();
     rtti_held = &typeid(T);
     rtti_uqp_del = &typeid(D);
-    vptr_deleter_flag = true;
-    vptr.reset(unq_ptr.get(), guarded_custom_deleter<T, D>(&vptr_deleter_flag));
+    vptr_deleter_guard_flag = true;
+    vptr.reset(unq_ptr.get(),
+               guarded_custom_deleter<T, D>(&vptr_deleter_guard_flag));
     unq_ptr.release();
   }
 
@@ -143,10 +143,25 @@ struct smart_holder {
     ensure_compatible_rtti_uqp_del<D>(context);
     ensure_use_count_1(context);
     T* raw_ptr = static_cast<T*>(vptr.get());
-    vptr_deleter_flag = false;
+    vptr_deleter_guard_flag = false;
     vptr.reset();
     return std::unique_ptr<T, D>(raw_ptr);
   }
+
+  template <typename T>
+  void from_shared_ptr(std::shared_ptr<T> shd_ptr) {
+    clear();
+    rtti_held = &typeid(T);
+    vptr = std::static_pointer_cast<void>(shd_ptr);
+  }
+
+  template <typename T>
+  std::shared_ptr<T> as_shared_ptr() {
+    static const char* context = "as_shared_ptr";
+    ensure_compatible_rtti_held<T>(context);
+    return std::static_pointer_cast<T>(vptr);
+  }
 };
 
-PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
+}  // namespace memory
+}  // namespace pybindit

tests/test_smart_holder_poc.cpp

@@ -17,9 +17,9 @@ struct functor_builtin_delete {
 
 inline void exercise() {
   to_cout("");
-  namespace py = pybind11;
+  using pybindit::memory::smart_holder;
   {
-    py::smart_holder hld;
+    smart_holder hld;
     hld.from_raw_ptr_owned(new int(13));
     to_cout(hld.rtti_held->name());
     {
@@ -33,24 +33,24 @@ inline void exercise() {
   }  // namespace ;
   {
     std::unique_ptr<int> val(new int(13));
-    py::smart_holder hld;
+    smart_holder hld;
     hld.from_raw_ptr_unowned(val.get());
     to_cout(std::to_string(*hld.as_raw_ptr_unowned<int>()));
   }
   {
     std::unique_ptr<int> val(new int(13));
-    py::smart_holder hld;
+    smart_holder hld;
     hld.from_unique_ptr(std::move(val));
     to_cout(std::to_string(*hld.as_raw_ptr_unowned<int>()));
   }
   {
-    py::smart_holder hld;
+    smart_holder hld;
     hld.from_raw_ptr_owned(new int(13));
     to_cout(std::to_string(*hld.as_unique_ptr<int>()));
   }
   {
     std::unique_ptr<int, functor_builtin_delete<int>> unq_ptr(new int(13));
-    py::smart_holder hld;
+    smart_holder hld;
     hld.from_unique_ptr_with_deleter(std::move(unq_ptr));
     to_cout(std::to_string(unq_ptr.get() == nullptr));
     to_cout(std::to_string(*hld.as_raw_ptr_unowned<int>()));
@@ -59,6 +59,12 @@ inline void exercise() {
     to_cout(std::to_string(hld.vptr.get() == nullptr));
     to_cout(std::to_string(*unq_ptr_retrieved));
   }
+  {
+    std::shared_ptr<int> val(new int(13));
+    smart_holder hld;
+    hld.from_shared_ptr(val);
+    to_cout(std::to_string(*hld.as_raw_ptr_unowned<int>()));
+  }
 }
 
 TEST_SUBMODULE(smart_holder_poc, m) { m.def("exercise", exercise); }