Suppress sanitizer errors about pointer arithmetic in a few places

We perform weird pointer arithmetic due to the layout of Lisp_Objects
holding symbols.  ASan/UBSan warns about that (Bug#42530).  Suppress
the warnings by performing the arithmetic on integer types and casting
back to pointers.

* src/alloc.c (mark_maybe_object, mark_memory): Temporarily cast
pointer to 'intptr_t'.

1 files changed, 3 insertions, 2 deletions

diff --git a/src/alloc.c b/src/alloc.c
index 76bb20876b0..5b9c6e4eb1f 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -4638,7 +4638,8 @@ mark_maybe_object (Lisp_Object obj)
       break;
     }
 
-  void *po = (char *) XLP (obj) + (offset - LISP_WORD_TAG (type_tag));
+  void *po = (char *) ((intptr_t) (char *) XLP (obj)
+                       + (offset - LISP_WORD_TAG (type_tag)));
 
   /* If the pointer is in the dump image and the dump has a record
      of the object starting at the place where the pointer points, we
@@ -4849,7 +4850,7 @@ mark_memory (void const *start, void const *end)
          On a host with 32-bit pointers and 64-bit Lisp_Objects,
          a Lisp_Object might be split into registers saved into
          non-adjacent words and P might be the low-order word's value.  */
-      p += (intptr_t) lispsym;
+      p = (char *) ((intptr_t) p + (intptr_t) lispsym);
       mark_maybe_pointer (p);
 
       verify (alignof (Lisp_Object) % GC_POINTER_ALIGNMENT == 0);