Hi. I just built GHC from master (1c35f9f1cb7a293da85d649904ce731a65824cfe) in my somewhat outdated MSYS2. I followed the wiki page with a few exceptions. - I cleared my PATH before running the shell (I left only Windows and System32) - my installation is not up-to-date - I do not have msys2 libtool, automake nor binutils; if the build used any of those, they came from mingw64 or from the host ghc - I had to run boot in pure msys2 shell, because mingw64 perl caused it to fail I saw no segfaults, but I may have missed them. I did not get a ghc.exe, but that may be correct behavior for all I know. My simple test program compiled and ran fine. I saw a lot of warnings during ghc's build though: - checking for DocBook DTD... I/O error : Attempt to load network entity http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd - something with not finding any implementation of a module out of [ xxx.dylib, xxx, ... ], I think it was in cabal builds - "could not find link destionations for: xxx" I hope it helps somehow. Maybe your issues come from mixing msys2 and mingw toolchain after all. -- David Macek