[Bf-blender-cvs] [dc64673f6e0] master: Fix T97691: undefined behavior sanitizer warning for alignment in RNA functions

[Brecht Van Lommel]

Commit: dc64673f6e096408f5bf5ba646512aebac4e0a59
Author: Brecht Van Lommel
Date:   Wed Jun 22 19:02:52 2022 +0200
Branches: master
https://developer.blender.org/rBdc64673f6e096408f5bf5ba646512aebac4e0a59

Fix T97691: undefined behavior sanitizer warning for alignment in RNA functions

Thanks Loren Osborn for investigating this and proposing solutions.

Ref D14798

===================================================================

M	source/blender/makesrna/intern/makesrna.c
M	source/blender/makesrna/intern/rna_access.c
M	source/blender/makesrna/intern/rna_define.c
M	source/blender/makesrna/intern/rna_internal.h

===================================================================

diff --git a/source/blender/makesrna/intern/makesrna.c b/source/blender/makesrna/intern/makesrna.c
index 400944d60d4..b5354514205 100644
--- a/source/blender/makesrna/intern/makesrna.c
+++ b/source/blender/makesrna/intern/makesrna.c
@@ -3030,7 +3030,7 @@ static void rna_def_function_funcs(FILE *f, StructDefRNA *dsrna, FunctionDefRNA
     }
 
     if (dparm->next) {
-      fprintf(f, "\t_data += %d;\n", rna_parameter_size(dparm->prop));
+      fprintf(f, "\t_data += %d;\n", rna_parameter_size_pad(rna_parameter_size(dparm->prop)));
     }
   }
 
diff --git a/source/blender/makesrna/intern/rna_access.c b/source/blender/makesrna/intern/rna_access.c
index 0bc35d86490..a0b25cf60b2 100644
--- a/source/blender/makesrna/intern/rna_access.c
+++ b/source/blender/makesrna/intern/rna_access.c
@@ -7130,7 +7130,7 @@ ParameterList *RNA_parameter_list_create(ParameterList *parms,
 
   /* allocate data */
   for (parm = func->cont.properties.first; parm; parm = parm->next) {
-    alloc_size += rna_parameter_size(parm);
+    alloc_size += rna_parameter_size_pad(rna_parameter_size(parm));
 
     if (parm->flag_parameter & PARM_OUTPUT) {
       parms->ret_count++;
@@ -7206,7 +7206,7 @@ ParameterList *RNA_parameter_list_create(ParameterList *parms,
       }
     }
 
-    data = ((char *)data) + rna_parameter_size(parm);
+    data = ((char *)data) + rna_parameter_size_pad(size);
   }
 
   return parms;
@@ -7230,7 +7230,7 @@ void RNA_parameter_list_free(ParameterList *parms)
       }
     }
 
-    tot += rna_parameter_size(parm);
+    tot += rna_parameter_size_pad(rna_parameter_size(parm));
   }
 
   MEM_freeN(parms->data);
@@ -7272,7 +7272,7 @@ void RNA_parameter_list_begin(ParameterList *parms, ParameterIterator *iter)
 
 void RNA_parameter_list_next(ParameterIterator *iter)
 {
-  iter->offset += iter->size;
+  iter->offset += rna_parameter_size_pad(iter->size);
   iter->parm = iter->parm->next;
   iter->valid = iter->parm != NULL;
 
diff --git a/source/blender/makesrna/intern/rna_define.c b/source/blender/makesrna/intern/rna_define.c
index 9d26797aa88..a747a5d11d8 100644
--- a/source/blender/makesrna/intern/rna_define.c
+++ b/source/blender/makesrna/intern/rna_define.c
@@ -4421,6 +4421,16 @@ int rna_parameter_size(PropertyRNA *parm)
   return sizeof(void *);
 }
 
+int rna_parameter_size_pad(const int size)
+{
+  /* Pad parameters in memory so the next parameter is properly aligned.
+   * This silences warnings in ubsan. More complicated logic to pack parameters
+   * more tightly in memory is unlikely to improve performance, and aligning
+   * to the requirements for pointers is enough for all data types we use. */
+  const int alignment = sizeof(void *);
+  return (size + alignment - 1) & ~(alignment - 1);
+}
+
 /* Dynamic Enums */
 
 void RNA_enum_item_add(EnumPropertyItem **items, int *totitem, const EnumPropertyItem *item)
diff --git a/source/blender/makesrna/intern/rna_internal.h b/source/blender/makesrna/intern/rna_internal.h
index 9e743a4f205..6ca8e668fa0 100644
--- a/source/blender/makesrna/intern/rna_internal.h
+++ b/source/blender/makesrna/intern/rna_internal.h
@@ -635,6 +635,7 @@ PointerRNA rna_pointer_inherit_refine(struct PointerRNA *ptr, struct StructRNA *
 /* Functions */
 
 int rna_parameter_size(struct PropertyRNA *parm);
+int rna_parameter_size_pad(const int size);
 
 /* XXX, these should not need to be defined here~! */
 struct MTex *rna_mtex_texture_slots_add(struct ID *self,