Typo in data layout document

[Mark Mitchell]

Under virtual base allocation:

  Any indirect primary base class E of the current class C, has been
  chosen as the primary base class of some other base class (direct or
  indirect, virtual or non-virtual) of C, will be allocated as part of
  that other base class, and is not allocated here.

That's not a sentence. :-) There should be a `that' before `has been
chosen'.

I think it would be useful to note the following example near that
paragraph.  (The C++ standard contains examples intermixed with the
rules, and it makes it much easier to read.)

  Consider:

    struct R { virtual void r (); };
    struct S { virtual void s (); };
    struct T : virtual public S { virtual void t (); };
    struct U : public R, virtual public T { virtual void u (); };

  R is the primary base class for U since it is the first direct
  non-virtual dynamic base.  Then, since an inheritance-order walk of
  U is { U, R, T, S } the T base is allocated next.  Since S is a 
  primary base of T, there is no need to allocate it separately.
  However, given:

    struct V : public R, virtual public S, virtual public T { 
      virtual void v ();
    };

  the inheritance-order walk of V is { V, R, S, T } so S is allocated
  first as a virtual base.  Then, T is allocated separately.  Thus
  sizeof (V) > sizeof (U).

--
Mark Mitchell                   mark at codesourcery.com
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