Implement C++ methods for DNA structures

This change makes it possible to add implementation of common
C++ methods for DNA structures which helps ensuring unsafe
operations like shallow copy are done explicitly.

For example, creating a shallow copy used to be:

  Object temp_object = *input_object;

In the C++ context it was seen like the temp_object is
properly decoupled from the input object, while in the
reality is it not. Now this code becomes:

  Object temp_object = blender::dna::shallow_copy(*input_object);

The copy and move constructor and assignment operators are
now explicitly disabled.

Other than a more explicit resource management this change
also solves a lot of warnings generated by the implicitly
defined copy constructors w.r.t dealing with deprecated fields.
These warnings were generated by Apple Clang when a shallow
object copy was created via implicitly defined copy constructor.

In order to enable C++ methods for DNA structures a newly added
macro `DNA_DEFINE_CXX_METHODS()` is to be used:

  tpyedef struct Object {
    DNA_DEFINE_CXX_METHODS(Object)
    ...
  } Object;

For the shallow copy use `blender::dna::shallow_copy()`.

The implementation of the memcpy is hidden via an internal DNA
function to avoid pulling `string.h` into every DNA header.
This means that the solution does not affect on the headers
dependencies.

---

Ideally `DNA_shallow_copy` would be defined in a more explicit
header, but don;t think we have a suitable one already. Maybe
we can introduce `DNA_access.h` ?

Differential Revision: https://developer.blender.org/D14427

1 files changed, 2 insertions, 2 deletions

diff --git a/source/blender/editors/object/object_transform.cc b/source/blender/editors/object/object_transform.cc
index 24425b5a991..afd2c048379 100644
--- a/source/blender/editors/object/object_transform.cc
+++ b/source/blender/editors/object/object_transform.cc
@@ -1695,13 +1695,13 @@ static void object_apply_rotation(Object *ob, const float rmat[3][3])
 static void object_apply_location(Object *ob, const float loc[3])
 {
   /* quick but weak */
-  Object ob_prev = *ob;
+  Object ob_prev = blender::dna::shallow_copy(*ob);
   float mat[4][4];
   copy_m4_m4(mat, ob->obmat);
   copy_v3_v3(mat[3], loc);
   BKE_object_apply_mat4(ob, mat, true, true);
   copy_v3_v3(mat[3], ob->loc);
-  *ob = ob_prev;
+  *ob = blender::dna::shallow_copy(ob_prev);
   copy_v3_v3(ob->loc, mat[3]);
 }