See code in compiler explorer: https://www.godbolt.org/z/z8xf31bG4

struct of size of 0 does have its usage and it is supported by GNU C (https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html). However, make_unique makes it impossible to create such an unique_ptr because its default_delete requires "A" must have non-zero size.

struct A{
alignas(int[0]) int ptr[0];
};
void test(){
	unique_ptr<A> ptr=make_unique<A>();
}

 error: static assertion failed: can't delete pointer to incomplete type
   83 |         static_assert(sizeof(_Tp)>0,
      |                       ~~~~~~~~~~~^~

I am not arguing that static_assert is reasonable. My point is that "make_shared" can actually deal this properly. i.e.

shared_ptr ptr=make_shared<A>();

gives no error at all.

p.s. I just realized that it is rather a library issue than a parser one as clang is directly using this library. Does clang plan to fix this library apart from GCC?