llvm on CentOS 7

[Gedare Bloom]

On Mon, Sep 16, 2019 at 4:16 PM Chris Johns <chrisj at rtems.org> wrote:
>
> On 17/9/19 12:36 am, Joel Sherrill wrote:
> > Running log as I work through this.
>
> Thanks, it is appreciated.
>
> > Build failed because I didn't have cmake. Double-checked and sb-check wouldn't
> > have reported this. Not sure we should report it missing unless we can designate
> > something as "needed by some packages" or let folks know which one(s).
>
> Cmake is tagged as optional as llvm is optional.
>

Is there a (simple) way for sb-check to take arguments to check
pre-requisites on specific packages?

> The __cmake define in source-builder/defaults.mc could be changes to remove the
> absolute path and the environment's path will be searched. This is already done
> in FreeBSD, MacOS and I think Windows so maybe this should be the default.
>
> > Loaded cmake, then got this beauty:
> >
> > /usr/bin/cmake -Wno-dev -G 'Unix Makefiles' -DCMAKE_BUILD_TYPE=Release
> > -DCMAKE_INSTALL_PREFIX=/home/joel/rtems-work/tools/5
> > '-DPACKAGE_VERSION=8.0.1 (RTEMS 5, RSB
> > 4b7af073000d612b21b9dece538d2bcc85c0c240)'
> > -DLLDB_CODESIGN_IDENTITY=llvm ../llvm-8.0.1
> > -- Configuring incomplete, errors occurred!
> > CMake Error at CMakeLists.txt:3 (cmake_minimum_required):
> >   CMake 3.4.3 or higher is required.  You are running version 2.8.12.2
> >
> > Plenty of people on the net say to download and build it but it turns
> > out that EPEL
> > has a cmake3 RPM. That's a very respectable repo (unlike Ghettoforge which also
> > had it).
> >
> > yum erase cmake
> > yum install cmake3
> >
> > That installed /usr/bin/cmake3 which the build doesn't know about so I
> > symbolically
> > linked /usr/bin/cmake3 to ${HOME}/bin/cmake.
> >
> > This didn't work because it checks for /usr/bin/cmake so I made that
> > symlink to cmake3.
>
> If this is needed for a specific CentOS version I suggest you detect this in
> source-builder/sb/linux.py and set __cmake to cmake3. The llvm references
> %{__cmake}. I would prefer this over documenting symlinks.
>
> > This resulted in a failure further along.
> >
> > -- Detecting CXX compile features - done
> > CMake Error at cmake/modules/CheckCompilerVersion.cmake:40 (message):
> >   Host GCC version should be at least 5.1 because LLVM will soon use new C++
> >   features which your toolchain version doesn't support.  Your version is
> >   4.8.5.  You can temporarily opt out using
> >   LLVM_TEMPORARILY_ALLOW_OLD_TOOLCHAIN, but very soon your toolchain won't be
> >   supported.
> > Call Stack (most recent call first):
> >   cmake/modules/CheckCompilerVersion.cmake:45 (check_compiler_version)
> >   cmake/config-ix.cmake:13 (include)
> >   CMakeLists.txt:590 (include)
> >
>
> Ouch.
>
> > -- Configuring incomplete, errors occurred!
> > See also "/home/joel/rtems-work/rtems-source-builder/rtems/build/rtems-llvm-8.0.1-x86_64-linux-gnu-1/build/CMakeFiles/CMakeOutput.log".
> > shell cmd failed: /bin/sh -ex
> > /home/joel/rtems-work/rtems-source-builder/rtems/build/rtems-llvm-8.0.1-x86_64-linux-gnu-1/do-build
> > error: building rtems-llvm-8.0.1-x86_64-linux-gnu-1
> >
> > Looks like I need to move to a machine with newer gcc. There is a
> > floor on the host environment without doing some work. I think the
> > CentOS machine I use to do test builds of our tools from
> > gcc/binutils/newlib master should work since it has installs of
> > various newer gcc.
> >
> > That may take until I get home.
>
> Again thanks.
>
> FYI Windows with MSYS2 is not bilding even after upgrading it to latest packages
> and installing clang-8.0.2 as a package to build clang-8.0.2 with.
>
> On Windows the unpacking of the source has proved problematic because the cfe
> tarball contains links to files that are extracted after the link and on Windows
> that fails, the target needs to exist. I have added support to the RSB to handle
> this however the testsuite contains a bad link to a non-existent target for
> testing and this means the untar always fails. I have added a work around to the
> RSB for this but it is a little painful.
>
> I think this highlights there is a reasonable amount of work to get LLVM and
> clang building on all hosts. On the other hand MSYS2 is like other packaging
> systems, it provides clang-8.0.2 and it is built with all targets. Our users can
> then decide to use the packaged LLVM or build from source.
>
> Chris
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