[Bug c/116016] enhancement: add __builtin_set_counted_by(P->FAM, COUNT) or equivalent

[qinzhao at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116016

--- Comment #45 from qinzhao at gcc dot gnu.org ---
(In reply to Jakub Jelinek from comment #42)
> 
> But for the kernel you'll need to have fallback code which will set the
> actual counter manually for compilers without support for counted_by
> attribute or the new builtin,
The counter will not need to be set if there is no "counted_by" attribute. 
Only when "counted_by" attribute is added into kernel, the corresponding
counter field need to be set explicitly (that's a requirement for the
"counted_by" attribute).