[PATCH] D70791: Workaround for MSVC 16.3.* pre-c++17 type trait linkage

Wed Nov 27 10:55:03 PST 2019

erichkeane added a comment.

In D70791#1762081 <https://reviews.llvm.org/D70791#1762081>, @rnk wrote:

> I thought we agreed to remove the workaround that we had for this and just declare that the old MSVC STL release was buggy and users should update:
>  https://bugs.llvm.org/show_bug.cgi?id=42027
>  It's a point release that preserves ABI compatibility, so there's less motivation for us to add a compat hack.
>
> In general, we should seriously think about sunsetting some MS compat hacks that aren't needed for new SDK/STL versions to save on clang maintenance costs. The complexity they add is surprisingly expensive. For example, -fdelayed-template-parsing is a recurring source of compat issues in clang-tools-extra (see the commit logs), and I would like to revive D66394 <https://reviews.llvm.org/D66394> to get it disabled by default soon. (+ at thakis)

Ah!  I KNEW I had seen this bug before.  I searched the bug database for a while for it.

I agree with sunsetting MS compat hacks as well, though I think we would need to support at least the most recentish versions.  My test team tells me that this failure isn't fixed until the (yet to be released) 16.4 version of the MSVC, so at the moment we don't compile the 'current' version without -std=c++17.  I don't see why r363191 was reverted, though I believe that this is both a less intrusive change, and is heavily specialized to only deal with this one case so hopefully it would not get reverted for the same reason.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D70791/new/

https://reviews.llvm.org/D70791