llvm dev - Jun 2016 - [cfe-dev] clang++ build from source is not able to find C++ headers

Hello,

I am running OS X, when I build clang++ from source and use it to compile
.cpp files it fails as it is not able to find C++ header. I am not building
libc++ along with llvm and clang.

using -stdlib=libstdc++ solves problem partially but it fails when using
C++11 threads, again it can't find <thread>, to get this work clang++
should work with -stdlib=libc++ but it fails with previous error of not
finding C++ headers.

Is it required to build libc++ along with clang++?

clang++ with Xcode-command line tool works fine and it also work with
-stdlib=libc++.

How to solve this problem with my build clang++?

Sincerely,
Vivek
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On 23 June 2016 at 06:31, vivek pandya via cfe-dev
<cfe-dev at lists.llvm.org> wrote:
> I am running OS X, when I build clang++ from source and use it to compile
> .cpp files it fails as it is not able to find C++ header. I am not building
> libc++ along with llvm and clang.
When I'm not building with libcxx in-tree I find it easiest to just
symlink Xcode's libc++ headers into the build directory. Something
like "ln -s
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++
build/include".
> using -stdlib=libstdc++ solves problem partially but it fails when using
> C++11 threads, again it can't find <thread>, to get this work
clang++ should
> work with -stdlib=libc++ but it fails with previous error of not finding
C++
> headers.
Yes, the libstdc++ included with OS X is ancient (from GCC 4.2 I
think) and there only for compatibility reasons. It has virtually no
support for C++11, which LLVM needs.

Cheers.

Tim.

On Thu, Jun 23, 2016 at 7:36 PM, Tim Northover <t.p.northover at
gmail.com>
wrote:
> On 23 June 2016 at 06:31, vivek pandya via cfe-dev
> <cfe-dev at lists.llvm.org> wrote:
> > I am running OS X, when I build clang++ from source and use it to
compile
> > .cpp files it fails as it is not able to find C++ header. I am not
> building
> > libc++ along with llvm and clang.
>
> When I'm not building with libcxx in-tree I find it easiest to just
> symlink Xcode's libc++ headers into the build directory. Something
> like "ln -s
>
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++
> build/include".
>
Thanks Tim,

symlink to build include does not help because clang++ looks headers into
build/lib/clang/3.9.0/include ( as per output of clang++ -v) but I symlink
to /usr/local/include , that worked I hope there is nothing wrong in doing
so.

-Vivek
>
> > using -stdlib=libstdc++ solves problem partially but it fails when
using
> > C++11 threads, again it can't find <thread>, to get this
work clang++
> should
> > work with -stdlib=libc++ but it fails with previous error of not
finding
> C++
> > headers.
>
> Yes, the libstdc++ included with OS X is ancient (from GCC 4.2 I
> think) and there only for compatibility reasons. It has virtually no
> support for C++11, which LLVM needs.
>
> Cheers.
>
> Tim.
>
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