Is this a bug for __builtin_dynamic_object_size?

[Qing Zhao via Gcc-patches]

Hi, Sid,

For the following testing case:

#include <stdio.h>

#define noinline __attribute__((__noinline__))

static void noinline alloc_buf_more (int index)
{
  struct annotated {
    long foo;
    char b;
    char array[index];
    long c;
  } q, *p;

  p = &q;

  printf("the__bdos of p->array whole max is %d \n", 
__builtin_dynamic_object_size(p->array, 0)); 
  printf("the__bdos of p->array sub max is %d \n", 
__builtin_dynamic_object_size(p->array, 1));      
  printf("the__bdos of p->array whole min is %d \n", 
__builtin_dynamic_object_size(p->array, 2)); 
  printf("the__bdos of p->array sub min is %d \n", 
__builtin_dynamic_object_size(p->array, 3)); 

  return;
}

int main ()
{
  alloc_buf_more (10);
  return 0;
}

If I compile it with the latest upstream gcc and run it:

/home/opc/Install/latest-d/bin/gcc -O t.c
the__bdos of p->array whole max is 23 
the__bdos of p->array sub max is 23 
the__bdos of p->array whole min is 23 
the__bdos of p->array sub min is 23 

In which__builtin_dynamic_object_size(p->array, 0) and 
__builtin_dynamic_object_size(p->array, 1) return the same size, this seems 
wrong to me. 

There is one line in tree-object-size.cc might relate to this bug: (in the 
routine “addr_object_size”)

 603           if (! TYPE_SIZE_UNIT (TREE_TYPE (var))
 604               || ! tree_fits_uhwi_p (TYPE_SIZE_UNIT (TREE_TYPE (var)))
 605               || (pt_var_size && TREE_CODE (pt_var_size) == INTEGER_CST
 606                   && tree_int_cst_lt (pt_var_size,
 607                                       TYPE_SIZE_UNIT (TREE_TYPE (var)))))
 608             var = pt_var;

I suspect that the above line 604 “ ! tree_fits_uhwi_p (TYPE_SIZE_UNIT 
(TREE_TYPE (var)))” relates to this bug, since the TYPESIZE of the VLA “array” 
is not a unsigned HOST_WIDE_INT, but we still can use its TYPESIZE for 
dynamic_object_size?

What do you think?

Thanks.

Qing