[Bug c/124230] bound sanitizer does not issue error for out-of-bound access through pointer array annotated with counted_by

[qinzhao at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124230

--- Comment #2 from qinzhao at gcc dot gnu.org ---
the following patch fixed the issue:
    ELEMENT_SIZE:
     (sizetype) SAVE_EXPR <n> * 4
    get the index as (long unsigned int) m, and return it.
+   One special case is when the OFFSET is an integer constant, and the
+   element_size is also an interger constant, we should get the index
+   as OFFSET/element_size.
    The INDEX_P holds the pointer to the parent tree of the index,
    INDEX_N holds the position of the index in its parent.  */

@@ -666,9 +669,19 @@ static tree
 get_index_from_offset (tree offset, tree *index_p,
                       int *index_n, tree element_size)
 {
-  if (TREE_CODE (offset) != MULT_EXPR)
+  if (TREE_CODE (offset) != MULT_EXPR
+      && TREE_CODE (offset) != INTEGER_CST)
     return NULL_TREE;

+  if (TREE_CODE (offset) == INTEGER_CST
+      && TREE_CODE (element_size) != INTEGER_CST)
+    return NULL_TREE;
+
+  if (TREE_CODE (offset) == INTEGER_CST
+      && TREE_CODE (element_size) == INTEGER_CST)
+    return fold_build2 (EXACT_DIV_EXPR, TREE_TYPE (offset),
+                       offset, element_size);
+
   auto_vec<factor_t> e_factors, o_factors;