bpo-34170: Rework _PyCoreConfig_Read() to avoid side effect (GH-8353)

Rework _PyCoreConfig_Read() function which *reads* core configuration
to not *modify* the path configuration.

A new _PyCoreConfig_SetPathConfig() function now recreates the path
configuration from the core configuration. This function is now
called very late in _Py_InitializeCore(), just before calling
initimport().

Changes:

* Add _PyCoreConfig.dll_path
* Py_SetPath() now fails with a fatal python error on memory
   allocation failure.
* Rename _PyPathConfig_Calculate() to _PyPathConfig_Calculate_impl()
* Replace _PyPathConfig_Init() with _PyPathConfig_Calculate(): the
  function now requires a _PyPathConfig
* Add _PyPathConfig_SetGlobal() to set the _Py_path_config global
  variable.
* Add _PyCoreConfig_InitPathConfig(): compute the path configuration
* Add _PyCoreConfig_SetPathConfig(): set path configuration from core
  configuration
* Rename wstrlist_append() to _Py_wstrlist_append()
* _Py_wstrlist_append() now handles integer overflow.

1 files changed, 3 insertions, 0 deletions

diff --git a/Include/pystate.h b/Include/pystate.h
index 8158cab..ac09dc3 100644
--- a/Include/pystate.h
+++ b/Include/pystate.h
@@ -71,6 +71,9 @@ typedef struct {
     wchar_t *base_prefix;   /* sys.base_prefix */
     wchar_t *exec_prefix;   /* sys.exec_prefix */
     wchar_t *base_exec_prefix;  /* sys.base_exec_prefix */
+#ifdef MS_WINDOWS
+    wchar_t *dll_path;      /* Windows DLL path */
+#endif
 
     /* Private fields */
     int _disable_importlib; /* Needed by freeze_importlib */