https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78196
--- Comment #2 from David Malcolm <dmalcolm at gcc dot gnu.org> --- Sorry for the breakage. There seem to be two parts to this bug: (a) allow building with /dev/null on Windows, by having the driver pick a better name for the .s file. ( https://msdn.microsoft.com/en-us/library/aa365247.aspx seems to be the official docs on valid filenames on Windows ). (b) fix the build. Obviously this can be hacked around locally e.g. by removing "s-selftest" from "selftest" in gcc/Makefile.in. If (a) is hard to fix, we could pick a different source file e.g. have an "empty.c", and pass that in instead (this would avoid the need for the "-xc" also).