[cxx-abi-dev] lambda ABI inline function ODR compatibility issue

[Lawrence Crowl]

On 1/18/13, John McCall <rjmccall at apple.com> wrote:
> On Jan 18, 2013, at 10:51 AM, Michael Wong <michaelw at ca.ibm.com> wrote:
> > I should explain a little more my motivation for supporting
> > #3. I think #1 would require significant ABI committee work
> > and #2 would require significant Standard committee (and
> > implementation) work.
>
> That it might require us to do a modest amount of work isn't
> really a compelling reason to oppose a proposal.  The good reason
> to oppose proposal #2 (banning lambdas in weak-linkage functions)
> is that it takes away functionality for very obscure reasons,
> and the good reason to oppose proposal #1 (guaranteeing a layout)
> is that it's a potentially significant performance restriction
> imposed for, again, fairly obscure reasons.

Another reason to oppose #2 is that in a template context, you don't
know if the call is a lambda, and hence #2 imposes a restrictions
on many template definitions because of a few potential instances.

> Reasons to oppose #3 (internal linkage) include a) that it
> introduces a new source of undefined behavior and b) that it
> somewhat complicates the language design of the feature, albeit in
> a way that feels fairly natural given the anonymity of the type.
> I'm comfortable with both of these, but we should admit them.

-- 
Lawrence Crowl