The cpython/pystate.h includes cpython/initconfig.h using the relative path "cpython/initconfig.h", which probably works fine if your include path explicitly contains the top of the python directory, however when developing with a framework in macOS, the framework's root path cannot be referred to relatively.

Since cpython/pystate.h and cpython/initconfig.h live in the same directory, any C compiler should include them correctly, regardless of include path if the cpython/pystate.h includes "initconfig.h" instead of "cpython/initconfig.h", since I believe the very first path is always relative to the file including the next file.  In this case, cpython is the parent of pystate.h and thus including initconfig.h directly should work fine.

Previous 3.x versions worked fine, but the cpython directory wasn't in Headers for macOS.

Although I wasn't able to exhaustively test this on all platforms and with all compilers, changing the include in cpython/pystate.h to "initconfig.h" solved the compilation/include problem.