On Mon, 10 Apr 2017, Jason Merrill wrote:
> On Mon, Apr 10, 2017 at 8:50 AM, Richard Biener <rguent...@suse.de> wrote:
> > So here's my variant of a fix. I constrained the new flag
> > TYPE_TYPELESS_STORAGE to arrays and thus hope my localized fix in
> > build_cplus_array_type will suffice (if I have time I'll play with
> > template instantiation).
>
> Looks good. I would expect this to just work with templates, but it
> should of course be tested. In particular, std::aligned_storage needs
> to work.
The libstdc++ testsuite passes... (of course it did before as well).
I'll experiment with some trivial bits tomorrow.
> > * tree.c (build_cplus_array_type): Set TYPE_TYPELESS_STORAGE
> > for arrays of unsigned char or std::byte.
>
> I think it would be good to have a flag to select whether these
> semantics apply to any char variant and std::byte, only unsigned char
> and std::byte, or only std::byte.
Any suggestion? Not sure we really need it (I'm hesitant to write
all the testcases to verify it actually works).
Meanwhile re-testing with the following hunk to fix some LTO fallout.
Richard.
Index: gcc/tree.h
===================================================================
--- gcc/tree.h (revision 246808)
+++ gcc/tree.h (working copy)
@@ -4914,7 +4917,7 @@ inline bool
canonical_type_used_p (const_tree t)
{
return !(POINTER_TYPE_P (t)
- || TREE_CODE (t) == ARRAY_TYPE
+ || (TREE_CODE (t) == ARRAY_TYPE && ! TYPE_TYPELESS_STORAGE (t))
|| TREE_CODE (t) == VECTOR_TYPE);
}
