https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116016
--- Comment #60 from qinzhao at gcc dot gnu.org ---
I came up with the following draft for the documentation of the new
__builtin_get_counted_by, let me know your comments and suggestions:
Builtin-in Function: type __builtin_get_counted_by (ptr)
The argument PTR to the built-in function __builtin_get_counted_by is a pointer
to an array object, which should have a counted_by attribute associated with
it. This function returns a pointer to the corresponding object that holds the
number of elements in the array object through counted_by attribute.
The TYPE of the returned value should be a pointer type pointing to an integral
type.
It's the user's responsibility to make sure that the PTR has a counted-by
attribute associated with it.
(GCC provides another built-in __builtin_has_attribute() to make sure this)
For example:
for the following:
struct foo {
int counter;
struct bar1 array[] __attribute__((counted_by(counter)));
} *p;
__builtin_get_counted_by (p->array)
returns:
&p->counter
