On Mon, Apr 27, 2020 at 03:32:29PM -0400, Jason Merrill wrote:
> Note that C++20 adds empty non-static data members with the
> [[no_unique_address]] attribute. How will that fit into these ABIs and the
> others that had issues with parameter passing?
Are they also represented in the trees handed over to the middle-end
as FIELD_DECLs with bitsize_zero DECL_SIZE and TREE_TYPE that contains
padding (like the empty base field does)?
Or are they just like say C empty structs in other structs (bitsize_zero
DECL_SIZE and TYPE_SIZE of TREE_TYPE)?
I bet they aren't DECL_ARTIFICIAL, but should have the no_unique_address
attribute on them, so the backends or some helper function in calls.c
could again catch them and decide what to do.
I guess at least we don't have an ABI incompatibility between different
-std=* versions, and given that it seems clang++ also implements it,
it will be worth checking the passing against it.
Jakub
