From 1b9f85a09e0f41d73a40f3bd4b4ee7b62a1021ce Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Wed, 23 Jun 2021 17:24:04 -0700
Subject: [PATCH] Preparation for being smarter about casting to `void *` to
 evade to shared_from_this mechanism.

---
 include/pybind11/detail/smart_holder_poc.h    | 27 ++++++++++++-------
 .../detail/smart_holder_type_casters.h        |  6 ++---
 2 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/include/pybind11/detail/smart_holder_poc.h b/include/pybind11/detail/smart_holder_poc.h
index f594cb257..48805069f 100644
--- a/include/pybind11/detail/smart_holder_poc.h
+++ b/include/pybind11/detail/smart_holder_poc.h
@@ -254,13 +254,17 @@ struct smart_holder {
     }
 
     template <typename T>
-    static smart_holder from_raw_ptr_take_ownership(T *raw_ptr) {
+    static smart_holder from_raw_ptr_take_ownership(T *raw_ptr, bool void_cast_raw_ptr = false) {
         to_cout("");
         to_cout("LOOOK smart_holder from_raw_ptr_take_ownership " + std::to_string(__LINE__) + " "
                 + __FILE__);
         ensure_pointee_is_destructible<T>("from_raw_ptr_take_ownership");
         smart_holder hld;
-        hld.vptr.reset(static_cast<void *>(raw_ptr), make_guarded_builtin_delete<T>(true));
+        auto gd = make_guarded_builtin_delete<T>(true);
+        if (void_cast_raw_ptr)
+            hld.vptr.reset(static_cast<void *>(raw_ptr), std::move(gd));
+        else
+            hld.vptr.reset(raw_ptr, std::move(gd));
         hld.vptr_is_using_builtin_delete = true;
         hld.is_populated                 = true;
         return hld;
@@ -305,18 +309,21 @@ struct smart_holder {
     }
 
     template <typename T, typename D>
-    static smart_holder from_unique_ptr(std::unique_ptr<T, D> &&unq_ptr) {
+    static smart_holder from_unique_ptr(std::unique_ptr<T, D> &&unq_ptr,
+                                        bool void_cast_raw_ptr = false) {
         to_cout("LOOOK smart_holder from_unique_ptr " + std::to_string(__LINE__) + " " + __FILE__);
         smart_holder hld;
         hld.rtti_uqp_del                 = &typeid(D);
         hld.vptr_is_using_builtin_delete = is_std_default_delete<T>(*hld.rtti_uqp_del);
-        if (hld.vptr_is_using_builtin_delete) {
-            hld.vptr.reset(static_cast<void *>(unq_ptr.get()),
-                           make_guarded_builtin_delete<T>(true));
-        } else {
-            hld.vptr.reset(static_cast<void *>(unq_ptr.get()),
-                           make_guarded_custom_deleter<T, D>(true));
-        }
+        guarded_delete gd{nullptr, false};
+        if (hld.vptr_is_using_builtin_delete)
+            gd = make_guarded_builtin_delete<T>(true);
+        else
+            gd = make_guarded_custom_deleter<T, D>(true);
+        if (void_cast_raw_ptr)
+            hld.vptr.reset(static_cast<void *>(unq_ptr.get()), std::move(gd));
+        else
+            hld.vptr.reset(unq_ptr.get(), std::move(gd));
         unq_ptr.release();
         hld.is_populated = true;
         return hld;
diff --git a/include/pybind11/detail/smart_holder_type_casters.h b/include/pybind11/detail/smart_holder_type_casters.h
index 8cc161b34..19580c94d 100644
--- a/include/pybind11/detail/smart_holder_type_casters.h
+++ b/include/pybind11/detail/smart_holder_type_casters.h
@@ -314,7 +314,7 @@ struct smart_holder_type_caster_class_hooks : smart_holder_type_caster_base_tag
                     uninitialized_location, value_ptr_w_t, value_ptr_w_t)) {
                 if (inst->owned) {
                     new (uninitialized_location)
-                        holder_type(holder_type::from_raw_ptr_take_ownership(value_ptr_w_t));
+                        holder_type(holder_type::from_raw_ptr_take_ownership(value_ptr_w_t, true));
                 } else {
                     new (uninitialized_location)
                         holder_type(holder_type::from_raw_ptr_unowned(value_ptr_w_t));
@@ -328,7 +328,7 @@ struct smart_holder_type_caster_class_hooks : smart_holder_type_caster_base_tag
 
     template <typename T, typename D>
     static smart_holder smart_holder_from_unique_ptr(std::unique_ptr<T, D> &&unq_ptr) {
-        return pybindit::memory::smart_holder::from_unique_ptr(std::move(unq_ptr));
+        return pybindit::memory::smart_holder::from_unique_ptr(std::move(unq_ptr), true);
     }
 
     template <typename T>
@@ -801,7 +801,7 @@ struct smart_holder_type_caster<std::unique_ptr<T, D>> : smart_holder_type_caste
         void *&valueptr     = values_and_holders(inst_raw_ptr).begin()->value_ptr();
         valueptr            = src_raw_void_ptr;
 
-        auto smhldr = pybindit::memory::smart_holder::from_unique_ptr(std::move(src));
+        auto smhldr = pybindit::memory::smart_holder::from_unique_ptr(std::move(src), true);
         tinfo->init_instance(inst_raw_ptr, static_cast<const void *>(&smhldr));
 
         if (policy == return_value_policy::reference_internal)