On Wed, Nov 19, 2025 at 01:49:39PM +0100, Richard Biener wrote:
> Then, there is DECL_NONADDRESSABLE_P on a FIELD_DECL which for,
> say
>
> struct{
> int len;
> char *data;
> };
>
> could say that 'len' cannot have its address taken and thus the 'data' member
> cannot point to it. Not sure if it's possible to take the address of
> the length field
> of a std::string though, this mechanism isn't specific enough to only disallow
> 'data' from pointing to 'len'. DECL_NONADDRESSABLE_P is used by Ada
> (as is TYPE_NONALIASED_COMPONENT).
Makes me wonder if we couldn't set DECL_NONADDRESSABLE_P on private
FIELD_DECLs in classes where none of the methods take address of it and
either it doesn't have friends, or none of the friends take address of it
either. Though, I guess C++26 reflection breaks that assumption, one can
always use
&the_class_obj.[: std::meta::members_of (^^the_class,
std::meta::access_context::unchecked ())[N] :]
to bypass the access checking and still take the address of it.
Jakub
