From 3c1e75a2301c352dac72b1742cdd8efa2b335d6e Mon Sep 17 00:00:00 2001
From: Jacques Lucke <jacques@blender.org>
Date: Tue, 21 Sep 2021 17:50:53 +0200
Subject: Functions: make asserts more correct

It is valid to e.g. copy construct an integer in the same place,
because it is a trivial type. It does not work for types like std::string.

This fixes a crash reported in D12584 where it would copy a buffer
into itself. We should probably also avoid doing this copy alltogether
but that can be done separately.
---
 source/blender/functions/FN_cpp_type.hh      | 11 +++++------
 source/blender/functions/FN_cpp_type_make.hh |  1 +
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/source/blender/functions/FN_cpp_type.hh b/source/blender/functions/FN_cpp_type.hh
index 7277bf99c12..643b2fc1f28 100644
--- a/source/blender/functions/FN_cpp_type.hh
+++ b/source/blender/functions/FN_cpp_type.hh
@@ -96,6 +96,7 @@ class CPPType : NonCopyable, NonMovable {
   int64_t size_ = 0;
   int64_t alignment_ = 0;
   uintptr_t alignment_mask_ = 0;
+  bool is_trivial_ = false;
   bool is_trivially_destructible_ = false;
   bool has_special_member_functions_ = false;
 
@@ -340,7 +341,6 @@ class CPPType : NonCopyable, NonMovable {
    */
   void copy_assign(const void *src, void *dst) const
   {
-    BLI_assert(src != dst);
     BLI_assert(this->pointer_can_point_to_instance(src));
     BLI_assert(this->pointer_can_point_to_instance(dst));
 
@@ -371,7 +371,7 @@ class CPPType : NonCopyable, NonMovable {
    */
   void copy_construct(const void *src, void *dst) const
   {
-    BLI_assert(src != dst);
+    BLI_assert(src != dst || is_trivial_);
     BLI_assert(this->pointer_can_point_to_instance(src));
     BLI_assert(this->pointer_can_point_to_instance(dst));
 
@@ -402,7 +402,6 @@ class CPPType : NonCopyable, NonMovable {
    */
   void move_assign(void *src, void *dst) const
   {
-    BLI_assert(src != dst);
     BLI_assert(this->pointer_can_point_to_instance(src));
     BLI_assert(this->pointer_can_point_to_instance(dst));
 
@@ -433,7 +432,7 @@ class CPPType : NonCopyable, NonMovable {
    */
   void move_construct(void *src, void *dst) const
   {
-    BLI_assert(src != dst);
+    BLI_assert(src != dst || is_trivial_);
     BLI_assert(this->pointer_can_point_to_instance(src));
     BLI_assert(this->pointer_can_point_to_instance(dst));
 
@@ -464,7 +463,7 @@ class CPPType : NonCopyable, NonMovable {
    */
   void relocate_assign(void *src, void *dst) const
   {
-    BLI_assert(src != dst);
+    BLI_assert(src != dst || is_trivial_);
     BLI_assert(this->pointer_can_point_to_instance(src));
     BLI_assert(this->pointer_can_point_to_instance(dst));
 
@@ -495,7 +494,7 @@ class CPPType : NonCopyable, NonMovable {
    */
   void relocate_construct(void *src, void *dst) const
   {
-    BLI_assert(src != dst);
+    BLI_assert(src != dst || is_trivial_);
     BLI_assert(this->pointer_can_point_to_instance(src));
     BLI_assert(this->pointer_can_point_to_instance(dst));
 
diff --git a/source/blender/functions/FN_cpp_type_make.hh b/source/blender/functions/FN_cpp_type_make.hh
index 088f6b469f4..74dbcabf81a 100644
--- a/source/blender/functions/FN_cpp_type_make.hh
+++ b/source/blender/functions/FN_cpp_type_make.hh
@@ -195,6 +195,7 @@ CPPType::CPPType(CPPTypeParam<T, Flags> /* unused */, StringRef debug_name)
   debug_name_ = debug_name;
   size_ = (int64_t)sizeof(T);
   alignment_ = (int64_t)alignof(T);
+  is_trivial_ = std::is_trivial_v<T>;
   is_trivially_destructible_ = std::is_trivially_destructible_v<T>;
   if constexpr (std::is_default_constructible_v<T>) {
     default_construct_ = default_construct_cb<T>;
-- 
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