llvm on CentOS 7

[Peter Dufault]

> On Sep 16, 2019, at 10:36 , Joel Sherrill <joel at rtems.org> wrote:
> 
> Hi
> 
> Running log as I work through this.
> 
> 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).
> 
> 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.
> 
> 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)
> 
> 
> -- 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.

You can also install “devtoolset-7” from the CentOS Software Collection Sig (https://wiki.centos.org/SpecialInterestGroup/SCLo).  I have that installed.
devtoolset-7-binutils.x86_64             2.28-11.el7              @centos-sclo-rh

That will give you gcc 7.3.1 and friends:

[dufault at fubar ~]$ /opt/rh/devtoolset-7/root/bin/gcc --version
gcc (GCC) 7.3.1 20180303 (Red Hat 7.3.1-5)
Copyright (C) 2017 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

[dufault at fubar ~]$ 

Peter
-----------------
Peter Dufault
HD Associates, Inc.      Software and System Engineering

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