[llvm-dev] [libcxx-dev] Removing deprecated <ext/hash_set>, <ext/hash_map> and <ext/__hash>

Chandler Carruth via llvm-dev llvm-dev at lists.llvm.org
Tue Feb 5 20:18:07 PST 2019

FWIW, I'm pretty sure we still have plenty of code using them. We've not
done any analysis to see what timeframe that code could be be updated on --
our focus has been on *adopting* libc++ (and easing that path), not
removing the uses of weird things that it also supports. I'll point out
that I'd rather focus our energy on adopting libc++ than even doing this
analysis. ;]

I somewhat agree with Joerg that it would be good to understand the
motivation. Much like a bunch of our other compatibility things (GCC flags,
language extensions, etc.), having these headers helps encourage / ease
adoption which seems a generally good thing for libc++. I can imagine that
there is some large cost to keeping these around that would motivate
removing them, but I don't see anything about that in the above?


On Mon, Feb 4, 2019 at 11:32 AM Louis Dionne via libcxx-dev <
libcxx-dev at lists.llvm.org> wrote:

> Hi,
> Libc++ has been shipping the <ext/hash_set>, <ext/hash_map> and
> <ext/__hash> headers for a while and they are deprecated. Those headers
> contain data structures like __gnu_cxx::hash_map that have replacements
> like std::unordered_map. I would like to remove those headers. I've put up
> a patch for review but I won't commit it until we have a sort of plan
> because I know some people have expressed feelings about removing the
> headers in the past: https://reviews.llvm.org/D57688.
> FWIW, I've compiled a large code base with that patch and I didn't get any
> trouble. I suspect the amount of breakage this will cause is manageable
> especially if we give advance notice, but others might disagree.
> Is anybody opposed to removing those headers? If you're opposed to the
> removal, please explain why and what removal timeline/plan would work for
> you.
> Thanks!
> Louis
> _______________________________________________
> libcxx-dev mailing list
> libcxx-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/libcxx-dev
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20190205/326cf65b/attachment.html>

More information about the llvm-dev mailing list