hey All, the current settings for warnings etc for ghc validate do not work on mac, this is because some gcc flag isn't in clang, or vice versa, or some version of gcc related matter the relevant error is: error: unknown warning option '-Werror=unused-but-set-variable'; did you mean '-Werror=unused-const-variable'? [-Werror,-Wunknown-warning-option] the culprit seems to be apple clang, at least if my reading of the config output by validate is correct Configure completed successfully. Building GHC version : 8.5.20171223 Git commit id : d7d0aa316f9d23d73ae617e0cc1b147907667ef4 Build platform : x86_64-apple-darwin Host platform : x86_64-apple-darwin Target platform : x86_64-apple-darwin Bootstrapping using : /Users/carter/.install-ghc/ghc-8.2.2-hq/bin/ghc which is version : 8.2.2 Using (for bootstrapping) : /usr/bin/clang Using gcc : /usr/local/bin/gcc-7 which is version : 7.2.0 Building a cross compiler : NO Unregisterised : NO hs-cpp : /usr/local/bin/gcc-7 hs-cpp-flags : -E -undef -traditional there seem to be several take aways: 1) clang doesn't support unused-but-set-variable 1.5) no one has run validate on OSX in the past few months with a vanilla checkout / env? 2) how do i change the compiler selected for boot strapping, whether via env variables or other twiddles thanks! -Carter