Summary of the visible changes:

* sys.argv is now set earlier, before "import site"

* The implementation of the PEP 538 now respects -E and -I options.

* _PyCoreConfig now allows to modify a lot of configuration options which wasn't possible to configure previously. (_PyMainInterpreterConfig allows to configure options using Python types.) It should be very useful for embedded Python, once the API will be public.


Summary of the most important changes:

* On Unix, char **argv of main() is now decoded again and the configuration (cmdline, env vars, etc.) is read again if the C locale is coerced (PEP 538) or if the UTF-8 Mode is enabled (PEP 540).

* The "path configuration" (sys.path, sys.prefix, sys.exec_prefix, etc.) is now computed before _Py_InitializeMainInterpreter(), by _PyMainInterpreterConfig_Read()

* Warning options are now computed in a list from -W options and PYTHONWARNINGS env var, before setting sys.warnoptions. Similar change has been done for sys._xoptions: xoptions are first stored in a wchar_t** list.

* A new _PyInitError structure has been introduced to be able to report failures instead of calling Py_FatalError(). Most of the Python initializatioin code has been modified to use it.

* Py_Main() now only uses regular C functions (using wchar_t* type for example) before _Py_InitializeCore(), the Python C API is now only used after _Py_InitializeCore().

* A new _PyCoreConfig_Read() has been added to read most configuration options using C types. _PyMainInterpreterConfig_Read() is now mostly responsible to convert C types to Python types.

* It becomes simpler to decide the priority between env vars, -X options, command line options, Py_xxx global variables, etc. The code to read these options and to code to "merge" these options is now decoupled.

* Each interpreter now has its copy of the "core_config" (_PyCoreConfig) and the main "config" (_PyMainInterpreterConfig). When using multiple interpreters, it is important to get Python objects created with the right interpreter for the main config. The ownership of these configurations becomes more obvious.

* Many global buffers with a fixed size like "static wchar_t progpath[MAXPATHLEN+1];" in Modules/getpath.c have been replaced with memory allocated on the heap with functions to release memory.

* Python/pathconfig.c (360 lines) has been added. More code is shared between Windows and Unix to compute the module search path (sys.path).