Hello, congratulations for attempting to build Sage from source on Cygwin and thanks for reporting on the build failure.
Which version of Sage were you trying to build? Did you try SageMath 9.4 or SageMath 9.5.rc1? Fixing the Python 3.9 build failure you described is tracked at: Sage Trac ticket #33079 Fix python3 build failure on Cygwin https://trac.sagemath.org/ticket/33079 In general, Sage's build mechanism tries to use the ambient system Python, if available, to avoid building its own Python. However, the Python 3.9 in Cygwin, currently provided by the Cygwin package "python39-3.9.9-1", does not work for that purpose. That issue is discussed at: Sage Trac ticket #33078 Update package info for system python3 on Cygwin https://trac.sagemath.org/ticket/33078 There is a newer version which can serve to build Sage upon; that newer version is currently marked as a test version, so that it does not get installed by default when you upgrade your Cygwin packages. You can however choose to upgrade to it, as follows. - Close all Cygwin windows. - Open Cygwin's "setup.exe" installer, search for "python39", and select the version "python39-3.9.9-3 (TEST)". Please try again building SageMath 9.5.rc1 after changing that. Let us know if that works. Currently it does not work for me, but I hope it works for you, and if not I hope we gather enough data on the failure to figure out how to solve it. --Samuel -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/sage-devel/0b9bfc45-cf21-453b-b926-a3ce7e5b8d95n%40googlegroups.com.
