# 2016-04-22 Exceptional meeting regarding VC pinning mechanism

14:00 UTC

Hangout Link: [](https://hangouts.google.com/call/uqi4wwchj5hnpdetsbzmaer7hue)[https://hangouts.google.com/call/uqi4wwchj5hnpdetsbzmaer7hue](https://hangouts.google.com/call/uqi4wwchj5hnpdetsbzmaer7hue)

Subject: **How do we want to express recipes for particular VS versions.**

*   New conda-build release - may be necessary for VS builds: [](https://github.com/conda/conda-build/releases/tag/1.20.1)[https://github.com/conda/conda-build/releases/tag/1.20.1](https://github.com/conda/conda-build/releases/tag/1.20.1)

        *   Rebuild Eigen to test that the latest version works - if so we can drop [John Kirkham](https://conda-forge.hackpad.com/ep/profile/wv6uvIZX6h0)'s conda-smithy branch that tries to fix appveyor.
    *   This has all been done and works now. In some cases Python 3.4 64-bit  builds on Windows have issues. That is still not understood.

*   Current guidance at [](https://github.com/conda-forge/staged-recipes/wiki/VC-features)[https://github.com/conda-forge/staged-recipes/wiki/VC-features](https://github.com/conda-forge/staged-recipes/wiki/VC-features) and [](https://github.com/conda/conda/wiki/VC-features)[https://github.com/conda/conda/wiki/VC-features](https://github.com/conda/conda/wiki/VC-features). 
*   How   should a simple recipe look? The following is problematic in   conda-build currently because the VS version isn't determined until the   build environment has been resolved (i.e. after the metadata has been   parsed, currently):

*   Should conda-build automatically express the msvc_runtime dependency?
*   If we had pinning capabilities within conda-build, does that become easier?
*   Whatever we choose, how do we maintain compatibility with **defaults**?

Notes: