https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126331
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
__bos1 has behaved that way since forever, FAM always meant the array can be
any size as long as it fits into the allocation (i.e. into __bos0).
So, I'm quite sure changing this would break real-world code.
There is definitely quite a lot of code in the wild that relies on say struct S
{ struct T { int a; char b[]; } c; }; __builtin_object_size (sptr->c.b, 1)
being handled as FAM (which is not pedantically valid either), or within unions
etc.
