[cfe-dev] Q on patch for CWG 2352

[Shoaib Meenai via cfe-dev]

Also +Hans for the question about the release.

From: cfe-dev <cfe-dev-bounces at lists.llvm.org> on behalf of cfe-dev <cfe-dev at lists.llvm.org>
Reply-To: David Blaikie <dblaikie at gmail.com>
Date: Wednesday, March 4, 2020 at 1:33 PM
To: "Robinson, Paul" <paul.robinson at sony.com>, Richard Smith <richard at metafoo.co.uk>
Cc: cfe-dev <cfe-dev at lists.llvm.org>
Subject: Re: [cfe-dev] Q on patch for CWG 2352

+Richard Smith<mailto:richard at metafoo.co.uk> for visibility.


On Wed, Mar 4, 2020 at 12:56 PM Robinson, Paul via cfe-dev <cfe-dev at lists.llvm.org<mailto:cfe-dev at lists.llvm.org>> wrote:
Richard Smith made a patch in f041e9ad for CWG2352.
As a consequence of this patch, we had an obscure test failure,
and it's not clear to me that it's an intentional consequence.
So I figured I'd ask here.

Reduced test case:

bool foo(void * const * const *       &&) { return false; }
bool foo(void *       * const * const &)  { return true; }
bool bar() {
  return foo(reinterpret_cast<void***>(2));
}

Prior to the patch, the compiler selected the second overload;
after the patch, it selects the first overload.  Apparently there's
some subtle difference in the preferred-ness of one over the other,
and AFAICT the const-nesses aren't supposed to factor in any more?
so it's about the &-ref versus the &&-ref?

As I said, mainly I want to make sure this was intentional; if it
is, we can fiddle our test and that's the end of it.  But if it's
not intentional, this change is in the almost-final Clang 10.0
release, and might want to be fixed before it goes out.

Thanks,
--paulr

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