# 2016-06-09: Compiler special meeting

Time: 14:00 UTC

Hangout link: [](https://hangouts.google.com/call/v5olhwzpfzgzpoq5i3wthjpqpie)[https://hangouts.google.com/call/v5olhwzpfzgzpoq5i3wthjpqpie](https://hangouts.google.com/call/v5olhwzpfzgzpoq5i3wthjpqpie)

**Attendees**

*   Jonathan Helmus
*   [John Kirkham](https://conda-forge.hackpad.com/ep/profile/wv6uvIZX6h0)
*   [Johannes Koster](https://conda-forge.hackpad.com/ep/profile/vuQo2WAv29A) 
*   [Bjorn Gruning](https://conda-forge.hackpad.com/ep/profile/DMmBLyb21HK) 
*   [Michael Sarahan](https://conda-forge.hackpad.com/ep/profile/yHQTJXZ4gyS)
*   Ray
*   Phil Elson

**Agenda**

Compiler docker images:

*   Conda-forge

        *   `docker pull condaforge/linux-anvil`
    *   Built on Quay ( [](https://quay.io/repository/condaforge/linux-anvil)[https://quay.io/repository/condaforge/linux-anvil](https://quay.io/repository/condaforge/linux-anvil) )
    *   Mirrored ( [](https://hub.docker.com/r/condaforge/linux-anvil/)[https://hub.docker.com/r/condaforge/linux-anvil/](https://hub.docker.com/r/condaforge/linux-anvil/) )
    *   CentOS 6, GCC 4.4.7, Devtoolset2 (GCC 4.8)
    *   Source code ( [](https://github.com/conda-forge/docker-images/tree/fbde090bd608caa720d5caad861aa382a8bf3f5c/linux-anvil)[https://github.com/conda-forge/docker-images/tree/fbde090bd608caa720d5caad861aa382a8bf3f5c/linux-anvil](https://github.com/conda-forge/docker-images/tree/fbde090bd608caa720d5caad861aa382a8bf3f5c/linux-anvil) )

*   Bioconda: [](https://hub.docker.com/r/bioconda/bioconda-builder/)[https://hub.docker.com/r/bioconda/bioconda-builder/](https://hub.docker.com/r/bioconda/bioconda-builder/)

        *   CentOS 5, GCC 4.4, Devtoolset2 (GCC 4.8)
    *   GCC 4.8 on PATH by default

Centers of discussion:

*   Need of libstdc++ updates / shadowing
*   Language compatibility needs (C++11/14)

As time allows: MSYS2 on Windows

**Notes**

<u>Overview of the Docker images</u>

*   conda-forge and bioconda seems to use same GCC version

<u>Key points:</u>

*   Need to monitor if we need to ship libstdc++ 

        *   Not needed if use Devtoolset 
    *   But users may still need to install if they are missing this library, like Arch linux, so we may want to ship this anyway

*   Need to say what language standard we are going to support C++14?
*   Legacy ABI support for old libraries (dual API, issues with older/newer ABI)

<u>History on conda-forge</u>

*   Initial conda-forge used gcc package
*   sometimes this would cause issues if packages were not pinned
*   switched to devoolset2 which does the static linking trick, 

<u>Future</u>

*   Use devtoolset4? (GCC 5.3, available on CentOS6)
*   Build our own compiler toolchain
*   GCC 6, could have some issues
*   Could have devtoolset2 and devtoolset4 installed in same Docker image

        *   Need to have some mechanism to activate a particular toolset

*   Using devtoolset does limit OS (CentOS5 only supports devtoolset2 not 4)
*   Could we build our own devtoolset?  

        *   Patches are available (srpm)
    *   Not small task, but do we want to take this on?
    *   Here is a link for some source ( [](https://git.centos.org/commit/rpms)[https://git.centos.org/commit/rpms](https://git.centos.org/commit/rpms%21devtoolset-4-gcc/e14f97005a3d22e658d01d0fc8899f5bda1982ca)[!devtoolset-4-gcc/e14f97005a3d22e658d01d0fc8899f5bda1982ca](https://git.centos.org/commit/rpms%21devtoolset-4-gcc/e14f97005a3d22e658d01d0fc8899f5bda1982ca) )

*   Using Docker image from Continuum

        *   Would  need to ship libstdc++ and keep it up to date to avoid shadowing system  version (need to be newer than users with newest version)
    *   Not many package in defaults link against libstdc++
    *   Have been shipping and has not seen issue yet...
    *   Julia has been doing this

*   libgfortran  was broken because defaults was shipping old version which causes  issues if user has more recent version of library installed
*   Could  we have a version of libstdc++ conda package which nothing depends on  but users could install if they are missing a system libstdc++?
*   Current infrastructure may not be able to support building gcc, but we could user other systems for this.

*   Continuum needs to support CentOS 5, conda-forge is happy with CentOS6 as minimum glibc version

*   John will do this. (After some discussion it became unclear whether this was best approach; so, holding off for now.)

*   Should have common build environment
*   How to support fortran on Mac

        *   New to use gfortran and have packages depend on libgfortran? package
    *   May be out of date, should we update?
    *   Port this solution to Linux?

                *   Either use patches or ship libstdc++

        *   Have same package for Mac and Linux OR use devtoolset magic?

                *   Want time to think and advantages and disadvantages for both

                        *   [Hackpad](https://conda-forge.hackpad.com/Devtools-vs-Ship-libstdc-Oz7Qqr4WrOr)

                *   Private vote by next Thursday, fill out [](http://goo.gl/forms/CexagdweBOKZZDjv1)[http://goo.gl/forms/CexagdweBOKZZDjv1](http://goo.gl/forms/CexagdweBOKZZDjv1)

*   Come up with a list of gcc 6.x problems that are encountered.
*   Why use clang vs gcc on Mac

        *   gcc has been remove in recent version of OS X

*   MSYS2

        *   Can be useful to get devtools 
    *   What about "alternative" MSYS2 Python environment
    *   Visual Studio and MSYS2 gcc are not compatible
    *   gfortran is big target (at least for Jonathan)
    *   msys2-w64 packages/channels on Anaconda Cloud
    *   OpenBLAS... does seem to be working on Windows
    *   Does this work with VS 2015?

*   Use ATLAS instead of OpenBLAS for windows numpy?

        *   Would need to repackage binary ATLAS DLL

*   Get some BLAS build even if it is not the best
*   How are SciPy Windows wheels being built?