[libcxx-dev] libcxx performance issue

[Marshall Clow via libcxx-dev]

On Sat, Aug 24, 2019 at 11:28 AM Yan Yichen via libcxx-dev <
libcxx-dev at lists.llvm.org> wrote:

> Dear developers,
>
>   Sorry to bother you, but I’ve met a wired problem using clang with
> libcxx.
>
>   I’ve built clang and libcxx with clang, and trying to compile c++
> program with libc++, but compilation is extremely slow when using libcxx,
> as below:
>
>
>
> $ time clang++ -o /dev/null -std=c++11 -stdlib=libc++ test.cc
>
> clang++ -o /dev/null -std=c++11 -stdlib=libc++ test.cc  4.29s user 0.06s
> system 97% cpu 4.476 total
>
> $ time clang++ -o /dev/null -std=c++11 test.cc
>
> clang++ -o /dev/null -std=c++11 test.cc  1.41s user 0.06s system 92% cpu
> 1.582 total
>
>
>
>   I wonder if you have any idea where should I start to address this
> issue, or anything I probably configured wrong? Thanks in advanced.
>
>
I'm afraid I have no idea what you're comparing *with*.

If you have an old libstdc++ (say), then that will be much faster, because
it's missing lots of C++11 features.
But that's just a guess.

-- Marshall
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/libcxx-dev/attachments/20190826/8a7cb2b6/attachment-0001.html>