https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109557
Bug ID: 109557
Summary: __builtin_dynamic_object_size() does not work for
simple testing case
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: qinzhao at gcc dot gnu.org
Target Milestone: ---
during my work for PR108896, I found that for the following small testing case:
[opc@qinzhao-ol8u3-x86 108896]$ cat test.c
#include <stdlib.h>
#include <assert.h>
struct P {
int k;
int x[10];
} *p;
void store(int a, int b)
{
p = (struct P *)malloc (sizeof (struct P));
p->k = a;
p->x[b] = 0;
assert (__builtin_dynamic_object_size (p, 0) == sizeof (struct P));
return;
}
int main()
{
store(7, 7);
assert (__builtin_dynamic_object_size (p, 0) == sizeof (struct P));
free (p);
}
with gcc13, compiled with -O, the above first assertion succeed, but the second
one failed.
when checking the tree-object-size.cc, I found:
1377 static void
1378 expr_object_size (struct object_size_info *osi, tree ptr, tree value)
1379 {
1380 int object_size_type = osi->object_size_type;
1381 unsigned int varno = SSA_NAME_VERSION (ptr);
1382 tree bytes, wholesize;
1383
1384 gcc_assert (!object_sizes_unknown_p (object_size_type, varno));
1385 gcc_assert (osi->pass == 0);
1386
1387 if (TREE_CODE (value) == WITH_SIZE_EXPR)
1388 value = TREE_OPERAND (value, 0);
1389
1390 /* Pointer variables should have been handled by merge_object_sizes. */
1391 gcc_assert (TREE_CODE (value) != SSA_NAME
1392 || !POINTER_TYPE_P (TREE_TYPE (value)));
1393
1394 if (TREE_CODE (value) == ADDR_EXPR)
1395 addr_object_size (osi, value, object_size_type, &bytes, &wholesize);
1396 else
1397 bytes = wholesize = size_unknown (object_size_type);
1398
1399 object_sizes_set (osi, varno, bytes, wholesize);
1400 }
in the above, for the 2nd __builtin_dynamic_object_size, the above line 1397 is
called, therefore size_unknown was returned for it.
I am wondering for
p.3_1 = p;
_2 = __builtin_object_size (p.3_1, 0);
why the size of p.3_1 cannot use the TYPE_SIZE of the pointee of p when its
size can be determined (i.e, not a structure with a flexible array member,
etc)?
