r210295 - Remove old proposal notices

[Richard Smith]

On Wed, Feb 4, 2015 at 9:36 PM, Richard Smith <richard at metafoo.co.uk> wrote:

> On Wed, Feb 4, 2015 at 6:38 PM, John McCall <rjmccall at apple.com> wrote:
>
>> > On Jun 5, 2014, at 4:17 PM, Richard Smith <richard at metafoo.co.uk>
>> wrote:
>> > On Thu, Jun 5, 2014 at 3:11 PM, Alp Toker <alp at nuanti.com> wrote:
>> > Author: alp
>> > Date: Thu Jun  5 17:11:20 2014
>> > New Revision: 210295
>> >
>> > URL: http://llvm.org/viewvc/llvm-project?rev=210295&view=rev
>> > Log:
>> > Remove old proposal notices
>> >
>> > Let's just go ahead and assume the answer was 'I do'
>> >
>> > :)
>> >
>> > You can check what proposals have made it into the ABI here:
>> >
>> >   http://mentorembedded.github.io/cxx-abi/abi.html
>> >
>> > For the ones that aren't in the ABI, having a comment explaining why
>> we're using them and where they come from is useful. None of these three
>> are in the ABI document yet; please back this out for now.
>> >
>> > John: any chance we could get the ABI document updated with these? (
>> http://sourcerytools.com/pipermail/cxx-abi-dev/2012-January/000024.html)
>>
>> After much delay, added.  We don’t seem to get this right, though, at
>> least not when the destination type isn’t dependent:
>>
>> template <class T, class U> T fst(T, U);
>> struct A {
>>   int x[3];
>> };
>> template <class T> decltype(fst(A{1,2},T())) foo(T t) {}
>>
>> int main() {
>>   foo(1);
>> }
>>
>> We produce:
>>   _Z3fooIiEDTcl3fstcv1AililLi1ELi2EEEcvT__EEES1_
>> It should be:
>>   _Z3fooIiEDTcl3fsttl1ALi1ELi2EcvT__EEES1_
>>
>
> There are quite a few bugs conspiring to give that result :( Our AST is
> also poorly-suited to this mangling, because the braces are not considered
> to be part of the functional cast itself; they're part of its subexpression.
>
> If you parenthesize the argument to A:
>>   template <class T> decltype(fst(A({1,2}),T())) foo(T t) {}
>> We produce:
>>   _Z3fooIiEDTcl3fstcv1AcvS0_ililLi1ELi2EEEcvT__EEES1_
>> It should be:
>>   _Z3fooIiEDTcl3fstcv1AliLi1ELi2EcvT__EEES1_
>>
>
> Somewhat related, we also get this wrong:
>
> struct X { X(int); };
> int f(X);
> template<typename T> void f(decltype(f(0), T())) { f(0); }
> void g() { f<int>(0); }
>
> ... because we explicitly mangle the implicit conversion from int to X. I
> see
>
> _Z1fIiEvDTcmcl1fLi0EEcvT__EE from EDG
> _Z1fIiEvDTcmclL_Z1f1XELi0EEcvT__EE from GCC
> _Z1fIiEvDTcmclL_Z1f1XEcvS0_cvS0_Li0EEcvT__EE from Clang
>
> I think GCC and Clang are right to use the resolved name L_Z1f1XE rather
> than the unresolved name 1f here, and GCC's mangling is right overall. Do
> you agree?
>

All of the above fixed in r228274. I'm not really very happy with our AST
representation here; we've overloaded CXXConstructExpr to mean too many
different syntactic things that it's hard to reconstruct the right mangling.

As an aside: if we have a fully-resolved call in an instantiation-dependent
expression, should we really be putting any used default arguments into the
mangling?
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