J3/14-170
To:      J3
From:    Van Snyder
Subject: Subobjects
Date: 2014 June 08

1. Introduction
===============

I'm not sure 6.4.2p5 says precisely what we want it to say.

Using the notation P# to indicate a <part-ref> that has the POINTER
attribute, and N# to indate one that does NOT have the pointer
attribute, it seems that

N1%N2 and P1%N2 designate subobjects of N1 and (the target of) P1,

N1%P2 and P1%P2 designate subobjects only in contexts that pertain to
their pointer association, and

N1%P2%N3, N1%P2%P3, P1%P2%N3 and P1%P2%P3 never designate subobjects.

That's not what 6.4.2p5 says.  It says a <data-ref> denotes a subobject
if the only <part-ref> that has the POINTER attribute is the rightmost
one.  That is, N1%N2 denotes a subobject, but P1%N2 does not.

I think we want to say something like "rightmost ... and no other
<part-name> except possibly the leftmost are pointers."

Further, 6.4.2p5 applies to subobjects only in the context of their
designators.  It does not pertain to subcomponents of designated
objects.  In particular, it does not specify that a subcomponent that
has the POINTER attribute is not a subobject of a designated object in
contexts that apply to the designated object's value.

2. Edits to 14-007r1
====================

[18:25 1.3.155] Append "; a component that has the POINTER attribute
is a subobject in contexts that pertain to its pointer association
status, but not in other contexts"

[121:21-23 6.4.2p5] Replace 6.4.2p5:

    "A <data-ref> with more than one <part-ref> is a subobject of its
    base object if none of the <part-name>s, except possibly the
    leftmost and rightmost, are pointers.  If the rightmost <part-name>
    is a pointer, and no other <part-name> except possibly the leftmost
    are pointers, then the <data-ref> designates a subobject of its base
    object in contexts that pertain to its pointer association status,
    but not in other contexts."

Index this occurrence of "subobject".