For years I have done 32-bit compilations of the Tcl interface using MSYS/MinGW, with ./configure and make. I want to the the same but 64-bit. There is MinGW-w64, but I have not been able to figure out to use it. It does not come with MSYS. I copied the msys folder from the 32-bit MinGW, and ran a compile from there. It seemed to run, but a 64-bit tclkit did not like the dll file. The error message suggested a possible 32/64-bit mismatch. Dependency Walker shows the top level as KERNEL32.DLL Any suggestions for how to fix this, or a better way to go?