On 2023-07-31 13:03, Siddhesh Poyarekar wrote:
On 2023-07-31 12:47, Qing Zhao wrote:
Hi, Sid and Jakub,
I have a question in the following source portion of the routine
“addr_object_size” of gcc/tree-object-size.cc:
743 bytes = compute_object_offset (TREE_OPERAND (ptr, 0), var);
744 if (bytes != error_mark_node)
745 {
746 bytes = size_for_offset (var_size, bytes);
747 if (var != pt_var && pt_var_size && TREE_CODE (pt_var)
== MEM_REF)
748 {
749 tree bytes2 = compute_object_offset (TREE_OPERAND
(ptr, 0),
750 pt_var);
751 if (bytes2 != error_mark_node)
752 {
753 bytes2 = size_for_offset (pt_var_size, bytes2);
754 bytes = size_binop (MIN_EXPR, bytes, bytes2);
755 }
756 }
757 }
At line 754, why we always use “MIN_EXPR” whenever it’s for
OST_MINIMUM or not?
Shall we use
(object_size_type & OST_MINIMUM
? MIN_EXPR : MAX_EXPR)
That MIN_EXPR is not for OST_MINIMUM. It is to cater for allocations
like this:
typedef struct
{
int a;
} A;
size_t f()
{
A *p = malloc (1);
return __builtin_object_size (p, 0);
Correction, that should be __builtin_object_size (&p->a, 0)
}
where the returned size should be 1 and not sizeof (int). The mode
doesn't really matter in this case.
HTH.
Sid
