https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79771
--- Comment #4 from Yaakov Selkowitz <yselkowi at redhat dot com> --- This is an upstream issue in the recent zlib releases, here's a patch: https://github.com/cygwinports/zlib/blob/master/1.2.11-gzopen_w.patch Configuring with --with-system-zlib avoids this, as long as gcc doesn`t try using the Win32-only gzopen_w on Cygwin (which it hasn't in the past).
