I have a bunch of linux regression runners that are executing clang runs of the boost regression suite (clang 3.0 - 4.0), currently these are all using the default, GCC libstdc++. Is there an interest from developers to see these runs with libc++? The basic options: 1) Convert all compatible clang builds to libc++, don't mess with libstdc++ & clang. 2) Duplicate all the clang builds to build each version with both (acknowledging that will add nearly 1/3 to the already large ~125 linux runs). 3) Change most of the runs, but keep a few token libstdc++ & clang runs, with the latest compiler version (what c++ standard c++14? c++1z?). 4) Just add a few token libc++ runs, with the latest compiler version (what c++ standard c++14? c++1z?). 5) Don't add libc++. For background (you can respond to one of the above preferences without reading on), there are two machines constantly running linux builds (in addition to the two windows ones) that I manage. One I consider the "full" suite of compilers. It runs clang 3.0 - 4.0 and gcc 4.4 - 6. For the oldest and latest releas (gcc 4.4, gcc 6, clang 3.0, clang 3.9), I run all the supported standard configs I could find (c++98, c++0x, gnu98, gnu0x -- c++03, c++11, c++14, c++1z and their gnu equivalents). I also do runs with optimization and warnings cranked, against the latest standard config e.g. "-std=c++1z -O2". For all the compiler versions that aren't on the endcaps, I just run a single config with whatever was the latest standard config for that compiler (e.g. gcc-4.8 with c++1y). This is all repeated for develop and master for a total of about 100 different configurations. The machine I consider the "fast results" machine is configured with only four runs, one each for the latest release of gcc and clang with the latest supported standard config (currently gcc-6 1z and clang-3.9 1z), for both master and develop. The goal here is that for any change checked in, the author will have feedback on its success against something modern and relevant within just a few hours. As a backup to the "fast results" machine, I also run those four regression modern runs, interspersed with the rest of the configs every dozen or so runs, bringing the total number of runs on the "full" machine up to around 125, which takes about a week for the machine to get through all the configurations. You can see more details about all of this on the github page where I keep my regression build scripts: https://github.com/teeks99/boost-build/tree/master/Regression The actual confgs run by the "full": https://github.com/teeks99/boost-build/blob/master/ Regression/teeks99-02/machine_vars.json The docker builds for all these machine configurations are kept at: https://github.com/teeks99/boost-build/tree/master/Docker And can be pulled from the docker hub with e.g. `docker pull teeks99/boost-build:clang-3.9` If you've read this far, I'd be happy for any other opinions from developers who use the test matrix. Is it worth keeping all those compilers in the middle? Do we need to test the latest compilers with all the different standard configs (03, 11, 14, 1z + gnu equivalents)? Thanks, Tom