Hi Simon, What happens when you try to compile that simple test with the bundled gcc? Could you also run it through strace, this will force msys2 not to swallow errors from the OS. Should you get an exception dialog then rm -rf inplace/mingw and rerun configure (I assume you’re on a recent revision). If none of the above give a clue, you could try ./configure --enable-distro-toolchain, this will have it skip the bundled GCC And use any installed by msys2. If this work then try rm’ing the GHC-tarballs folder and the inplace/mingw folder and try again With –enable-tarballs-autodownloads. Tamar. From: Simon Peyton Jones via ghc-devs Sent: Thursday, June 29, 2017 00:35 To: ghc-devs Subject: Windows broken Help please! Suddenly my Windows build has stopped working. See below. What should I do? I’m totally stuck. This has never happened before. I get this: GHC path canonicalised to: c:/fp/ghc-8.0.2/bin/ghc checking build system type... x86_64-pc-msys checking host system type... x86_64-pc-msys checking target system type... x86_64-pc-msys Build platform inferred as: x86_64-unknown-mingw32 Host platform inferred as: x86_64-unknown-mingw32 Target platform inferred as: x86_64-unknown-mingw32 GHC build : x86_64-unknown-mingw32 GHC host : x86_64-unknown-mingw32 GHC target : x86_64-unknown-mingw32 LLVM target: x86_64-unknown-mingw32 checking for path to top of build tree... C:/code/HEAD configure: Checking for Windows toolchain tarballs... configure: Extracting Windows toolchain from archives (may take a while)... configure: In-tree MingW-w64 tree created configure: Making in-tree perl tree configure: In-tree perl tree created checking whether the C compiler works... no configure: error: in `/c/code/HEAD': configure: error: C compiler cannot create executables See `config.log' for more details Something wrong with the gcc.exe? Config.log has this gcc version 6.3.0 (Rev2, Built by MSYS2 project) configure:4950: $? = 0 configure:4939: C:/code/HEAD/inplace/mingw/bin/gcc.exe -V >&5 gcc.exe: error: unrecognized command line option '-V' gcc.exe: fatal error: no input files compilation terminated. configure:4950: $? = 1 configure:4939: C:/code/HEAD/inplace/mingw/bin/gcc.exe -qversion >&5 gcc.exe: error: unrecognized command line option '-qversion'; did you mean '--version'? gcc.exe: fatal error: no input files compilation terminated. configure:4950: $? = 1 configure:4970: checking whether the C compiler works configure:4992: C:/code/HEAD/inplace/mingw/bin/gcc.exe conftest.c >&5 configure:4996: $? = 1 configure:5034: result: no configure: failed program was: | /* confdefs.h */ | #define PACKAGE_NAME "The Glorious Glasgow Haskell Compilation System" | #define PACKAGE_TARNAME "ghc-8.3" | #define PACKAGE_VERSION "8.3" | #define PACKAGE_STRING "The Glorious Glasgow Haskell Compilation System 8.3" | #define PACKAGE_BUGREPORT "glasgow-haskell-bugs@haskell.org" | #define PACKAGE_URL "" | /* end confdefs.h. */ | | int | main () | { | | ; | return 0; | } configure:5039: error: in `/c/code/HEAD': configure:5041: error: C compiler cannot create executables