[cfe-dev] Build system not picking up libc++?

[Jeffrey Walton]

Thanks Dan.

Perhaps it would be a good idea to touch up some of the documentation.

Other have been having problems (dating back to at least 2012), and
I've wasted 3 days on it (on and off). I can't speak for others, but I
can say for certain my problems are because the documentation is
telling me otherwise (I'm attempting to do things that should work).

-----

The first change should be in `configure --help`. State that you can't
specify the libcxx package and the libcxxabi package.

This is something me and other folks try when dropping libcxx into
llvm/projects and running configure fails to build the project.
There's really no manual for configure options, so we end up asking
dumb questions on CFE-Dev.

-----

The second change should be at http://llvm.org/docs/LLVMBuild.html
under Build Integrations. State that the project does not support
Makefiles under all cases. Specifically name libcxx and libcxxabi as
examples that don't support it.

This is a RTFM item, and its an important to state it. Otherwise,
folks like me go down rabbit holes that are dead ends. And then we ask
dumb questions on CFE-Dev.

-----

The third change should be at http://libcxx.llvm.org/. State the
libcxx and libcxxabi projects do not support Makefiles - period.

This is a RTFM item, and its an important to state it. Otherwise,
folks like me go down rabbit holes that are dead ends. And then we ask
dumb questions on CFE-Dev.

-----

There's a related change that could be helpful at
http://libcxx.llvm.org/. I seem to recall LLVM does not really support
building components in-tree (maybe this has changed, but I seem to
recall problems in the past). So, effectively, we need to drop libc++
in-tree so `make install` installs the headers, but we're not supposed
to build components from there.

So the helpful change would be: provide instruction when you have the
following directory structure (or similar):

  + clang-project
      |
      + build
      |
      + llvm


On Sat, Jan 10, 2015 at 8:28 PM, Dan Albert <danalbert at google.com> wrote:
> The configure scripts probably just don't support it. We've really only been
> adding features to the cmake flow for libc++.
>
> Also, if you're trying to use libc++abi as well, that project doesn't
> support configure at all, so you'll have to use cmake.
>
> On Jan 10, 2015 17:21, "Jeffrey Walton" <noloader at gmail.com> wrote:
>>
>> TLDR:
>>
>> I'm fetching packages from http://llvm.org/releases/download.html.
>>
>> Unpacking libcxx, placing it llvm/projects and running configure does
>> not pickup libc++. That is, 'make' does not build libc++. How do I
>> integrate libc++ into the build process?
>>
>> Manually running 'make cxx' per http://libcxx.llvm.org/ does not work.
>> There is no 'cxx' target. That's from both the top level llvm
>> directory and the llvm/projects/libcxx directory. Why does it not
>> work? (I know its kind of a broad question, but I don't know how to
>> start zeroing-in what's wrong).
>>
>> The llvm/projects/libcxx/Makefile does not have build rules (only
>> install rules). The LLVM projects support both Make and Cmake
>> (http://llvm.org/docs/LLVMBuild.html). I don't use Cmake, and I'm
>> using the Make based gear. What makefile should I be using?
>>
>> Trying to specify the packages with --with-libcxx --with-libcxxabi to
>> configure does not work. What are the package names? How do I specify
>> the packages so they are included during build?
>>
>> -----
>>
>> I have a recipe that builds LLVM, Compiler Front End (Clang), Compiler
>> RT and Extra tools. It works fine. I am trying to add libc++ to the
>> process because my Clang 3.5.0 install is having troubles on OX S 10.9
>> and 10.10 (it can't find C++ headers or libraries) (OS X 10.7 and 10.8
>> are OK).
>>
>> I downloaded libcxx-3.5.0.src.tar.xz from
>> http://llvm.org/releases/3.5.0/libcxx-3.5.0.src.tar.xz. I unpacked it,
>> and moved it to llvm/projects/libcxx (so its where the build system
>> expects it per http://libcxx.llvm.org/).
>>
>> I then configure with the following command (this is the same
>> configure that works without libc++):
>>
>>     # 'build' is next to 'llvm', and its the staging directory
>>     mkdir -p build
>>     cd build
>>     ../llvm/configure --enable-optimized --disable-assertions
>> --enable-cxx11 \
>>         $OTHER_OPTIONS --prefix=$(PREFIX)
>>
>> OTHER_OPTIONS is --enable-libcpp on OS X; and PREFIX is /usr/local.
>>
>> After configure and make, libc++ is not built. Performing a `find llvm
>> -iname libc++*` reveals no artifacts, like `libc++.a or libc++.dylib.
>> (It does find pre-existing files, like libc++abi.exp and
>> libc++abi2.exp from llvm/projects/libcxx/lib/).
>>
>> ----------
>>
>> I cannot run `make cxx` from the 'build' directory per
>> http://libcxx.llvm.org/. And manually running libc++'s make:
>>
>>     cd clang-scratch
>>     mkdir -p build
>>     DSTROOT=build; make -f llvm/projects/libcxx/Makefile
>>
>> Results in:
>>
>>     Use make install DSTROOT=<destination>
>>
>> Its as if the library was not even configured (it only has an install
>> recipe).
>>
>> ----------
>>
>> I tried adding packages to the configure line:
>>
>>     ../llvm/configure --enable-optimized --disable-assertions
>> --enable-cxx11 \
>>         --with-libcxx --with-libcxxabi $OTHER_OPTIONS --prefix=$(PREFIX)
>>
>> But that results in:
>>
>>     configure: WARNING: Unknown project (libcxx) won't be configured
>> automatically
>>     configure: WARNING: Unknown project (libcxxabi) won't be
>> configured automatically
>>
>> ----------
>>
>> A lot of this was already asked at "Questions about libc++ for linux
>> and its git repository (if any)",
>> http://lists.cs.uiuc.edu/pipermail/cfe-dev/2012-July/thread.html
>> (scroll down about 3/5'ths of the page). But most of the questions
>> went unanswered.