bpo-32030: Complete _PyCoreConfig_Read() (#4946)

* Add _PyCoreConfig.install_signal_handlers
* Remove _PyMain.config: _PyMainInterpreterConfig usage is now
  restricted to pymain_init_python_main().
* Rename _PyMain.core_config to _PyMain.config
* _PyMainInterpreterConfig_Read() now creates the xoptions dictionary
   from the core config
* Fix _PyMainInterpreterConfig_Read(): don't replace xoptions and
  argv if they are already set.

Include/pystate.h

@@ -25,6 +25,7 @@ typedef PyObject* (*_PyFrameEvalFunction)(struct _frame *, int);
 
 
 typedef struct {
+    int install_signal_handlers;  /* Install signal handlers? -1 means unset */
     int ignore_environment; /* -E */
     int use_hash_seed;      /* PYTHONHASHSEED=x */
     unsigned long hash_seed;
@@ -62,6 +63,7 @@ typedef struct {
 
 #define _PyCoreConfig_INIT \
     (_PyCoreConfig){ \
+        .install_signal_handlers = -1, \
         .use_hash_seed = -1, \
         .coerce_c_locale = -1, \
         .utf8_mode = -1, \
@@ -73,7 +75,7 @@ typedef struct {
  * See PEP 432 for final anticipated contents
  */
 typedef struct {
-    int install_signal_handlers;
+    int install_signal_handlers;   /* Install signal handlers? -1 means unset */
     PyObject *argv;                /* sys.argv list, can be NULL */
     PyObject *executable;          /* sys.executable str */
     PyObject *prefix;              /* sys.prefix str */

Python/pylifecycle.c

@@ -874,30 +874,29 @@ _Py_InitializeMainInterpreter(const _PyMainInterpreterConfig *config)
 _PyInitError
 _Py_InitializeEx_Private(int install_sigs, int install_importlib)
 {
-    _PyCoreConfig core_config = _PyCoreConfig_INIT;
-    _PyMainInterpreterConfig config = _PyMainInterpreterConfig_INIT;
+    _PyCoreConfig config = _PyCoreConfig_INIT;
     _PyInitError err;
 
-    core_config.ignore_environment = Py_IgnoreEnvironmentFlag;
-    core_config._disable_importlib = !install_importlib;
+    config.ignore_environment = Py_IgnoreEnvironmentFlag;
+    config._disable_importlib = !install_importlib;
     config.install_signal_handlers = install_sigs;
 
-    err = _PyCoreConfig_Read(&core_config);
+    err = _PyCoreConfig_Read(&config);
     if (_Py_INIT_FAILED(err)) {
         goto done;
     }
 
-    err = _Py_InitializeCore(&core_config);
+    err = _Py_InitializeCore(&config);
     if (_Py_INIT_FAILED(err)) {
         goto done;
     }
 
-    err = _PyMainInterpreterConfig_Read(&config, &core_config);
-    if (_Py_INIT_FAILED(err)) {
-        goto done;
+    _PyMainInterpreterConfig main_config = _PyMainInterpreterConfig_INIT;
+    err = _PyMainInterpreterConfig_Read(&main_config, &config);
+    if (!_Py_INIT_FAILED(err)) {
+        err = _Py_InitializeMainInterpreter(&main_config);
     }
-
-    err = _Py_InitializeMainInterpreter(&config);
+    _PyMainInterpreterConfig_Clear(&main_config);
     if (_Py_INIT_FAILED(err)) {
         goto done;
     }
@@ -905,8 +904,7 @@ _Py_InitializeEx_Private(int install_sigs, int install_importlib)
     err = _Py_INIT_OK();
 
 done:
-    _PyCoreConfig_Clear(&core_config);
-    _PyMainInterpreterConfig_Clear(&config);
+    _PyCoreConfig_Clear(&config);
     return err;
 }