On Wed, 20 Nov 2013, John McCall wrote:
Well, to be clear, these would be recommendations for people willing to
endure an ABI break. That would still be a big NO-NO for any
established platforms that care about binary compatibility.
And most of these changes are pretty minor improvements; the ABI has
really held up very well.
Indeed.
Maybe revisit some old issues?
A-9 has the comment: "this won't happen often", but it affects sizeof(tuple<tuple<int>>) in libstdc++.
Hmm, no, it doesn't, but it would if they swapped the order of their bases (currently for tuple<int,unsigned> they
store the unsigned before the int). Of the 3 permutations tuple<int,E,E>, tuple<E,int,E> and tuple<E,E,int>
where E is empty, only 1 has a small size, whereas I believe at most 1 should be large (0 would be great). And that's not the
only place I've hit this.
A-5: gcc and HP seemed to find it hard to implement at the time. Would that
still be the case? (it may need to mention move constructors now)
I seem to be missing the detail that makes it so complicated.
I am not sure how to interpret these comments. Would you mind
translating them into HTML #entity references, or at least section
numbers, of the living document at:
http://mentorembedded.github.io/cxx-abi/abi.html
A-5, A-9 were references to the issue list:
http://mentorembedded.github.io/cxx-abi/cxx-closed.html#A9
(A-5 has no anchor but is easy to find)
A-5 is about section 3.1.3 #empty-parameter, where we could omit some
empty arguments passed by value.
A-9 is about section 2.4.II.3 #class-types, where if offset 0 fails we
don't try offset nvalign(D), 2*nvalign(D), etc but jump straight to
dsize(C).
PS: sorry if my message has to go through moderation as a post by a
non-member, I am receiving the emails, and I even found the message from
when I registered, and I did use the same email address, so I don't know
why it is complaining.
--
Marc Glisse
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