bpo-34170: _PyCoreConfig_Read() leaves Py_IsolatedFlag unchanged (GH-8361)

* _PyCoreConfig_Read() no longer directly modifies Py_IsolatedFlag
  and Py_NoSiteFlag global configuration flags. The function now
  requires two pointers to integer, so these flags can be set later,
  to avoid side effets in _PyCoreConfig_Read().
* pathconfig_global_init() now leaves Py_IsolatedFlag and
  Py_NoSiteFlag unchanged.
* Fix pathconfig_global_init(): avoid computing the path
  configuration twice, use _PyCoreConfig_SetPathConfig().

2 files changed, 17 insertions, 3 deletions

diff --git a/Include/internal/pystate.h b/Include/internal/pystate.h
index 83fa7dc..6cee272 100644
--- a/Include/internal/pystate.h
+++ b/Include/internal/pystate.h
@@ -52,9 +52,17 @@ typedef struct _PyPathConfig {
     wchar_t *program_name;
     /* Set by Py_SetPythonHome() or PYTHONHOME environment variable */
     wchar_t *home;
+    /* isolated and no_site_import are used to set Py_IsolatedFlag and
+       Py_NoSiteFlag flags on Windows in read_pth_file(). These fields
+       are ignored when their value are equal to -1 (unset). */
+    int isolated;
+    int no_site_import;
 } _PyPathConfig;
 
-#define _PyPathConfig_INIT {.module_search_path = NULL}
+#define _PyPathConfig_INIT \
+    {.module_search_path = NULL, \
+     .isolated = -1, \
+     .no_site_import = -1}
 /* Note: _PyPathConfig_INIT sets other fields to 0/NULL */
 
 PyAPI_DATA(_PyPathConfig) _Py_path_config;
diff --git a/Include/pylifecycle.h b/Include/pylifecycle.h
index 9644116..2fbc4f9 100644
--- a/Include/pylifecycle.h
+++ b/Include/pylifecycle.h
@@ -54,12 +54,18 @@ PyAPI_FUNC(int) Py_SetStandardStreamEncoding(const char *encoding,
 PyAPI_FUNC(_PyInitError) _Py_InitializeCore(const _PyCoreConfig *);
 PyAPI_FUNC(int) _Py_IsCoreInitialized(void);
 
-PyAPI_FUNC(_PyInitError) _PyCoreConfig_Read(_PyCoreConfig *);
+PyAPI_FUNC(_PyInitError) _PyCoreConfig_Read(
+    _PyCoreConfig *config,
+    int *isolated,
+    int *no_site_import);
 PyAPI_FUNC(void) _PyCoreConfig_Clear(_PyCoreConfig *);
 PyAPI_FUNC(int) _PyCoreConfig_Copy(
     _PyCoreConfig *config,
     const _PyCoreConfig *config2);
-PyAPI_FUNC(_PyInitError) _PyCoreConfig_InitPathConfig(_PyCoreConfig *config);
+PyAPI_FUNC(_PyInitError) _PyCoreConfig_InitPathConfig(
+    _PyCoreConfig *config,
+    int *isolated,
+    int *no_site_import);
 PyAPI_FUNC(_PyInitError) _PyCoreConfig_SetPathConfig(
     const _PyCoreConfig *config);