Questions on replacing a structure pointer reference to a call to .ACCESS_WITH_SIZE in C FE

[Qing Zhao]

Hi, Joseph and Martin,

When I implemented the patch to attach the counted_by information to an array 
reference (FAM reference) in C FE, 
The work was done inside the routine “build_component_ref” in gcc/c/c-typeck.cc 
<http://c-typeck.cc/>.  and this is very reasonable and
quite clean. 

Now, If we try to replace a structure pointer reference with counted_by 
attached to the FAM field, where in the C FE
I should look at?

For the following small example, I am trying to replace the pointer reference 
at line 28, “obj”, and line 34, “q” to a call to
.ACCESS_WITH_SIZE. However, “p” at line 21 and “q” at line 33 should not be 
replaced. 

Do you have any suggestions?

Thanks a lot for your help here.

Qing

  1 #include <stdlib.h>
  2 #include <stddef.h>
  3    
  4 struct annotated {
  5   size_t count;
  6   char array[] __attribute__((counted_by (count)));
  7 };
  8 
  9 /* compute the minimum # of bytes needed to hold a structure “annotated”,
 10    whose # of elements of “array” is COUNT.  */
 11 #define MAX(A, B) (A > B) ? (A) : (B)
 12 #define ALLOC_SIZE_ANNOTATED(COUNT) \
 13   MAX(sizeof (struct annotated), \
 14       offsetof(struct annotated, array[0]) + (COUNT) * sizeof(char))
 15 
 16 /* allocate the memory for the structure with FAM,
 17    update “count” with the # of elements “index”.  */
 18 static struct annotated * __attribute__((__noinline__)) alloc_buf (int 
index)
 19 {
 20   struct annotated *p;
 21   p = (struct annotated *) malloc (ALLOC_SIZE_ANNOTATED(index));
 22   p->count = index;
 23   return p;
 24 }
 25 
 26 static size_t __attribute__((__noinline__)) size_of (struct annotated * obj)
 27 {
 28   return __builtin_dynamic_object_size (obj, 1);
 29 }
 30  
 31 int main()
 32 {
 33   struct annotated *q = alloc_buf (10);
 34   __builtin_printf ("the bdos whole is %d\n", size_of (q));
 35   return 0;
 36 }