bpo-36763: Add _Py_InitializeMain() (GH-13362)

* Add a private _Py_InitializeMain() function.
* Add again _PyCoreConfig._init_main.
* _Py_InitializeFromConfig() now uses _init_main to decide
  if _Py_InitializeMainInterpreter() should be called.
* _PyCoreConfig: rename _frozen to pathconfig_warnings, its value is
  now the opposite of Py_FrozenFlag.
* Add an unit test for _init_main=0 and _Py_InitializeMain().

1 files changed, 16 insertions, 1 deletions

diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index a173eb380a..e89152637f 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -970,6 +970,21 @@ _Py_InitializeMainInterpreter(_PyRuntimeState *runtime,
     return _Py_INIT_OK();
 }
 
+
+_PyInitError
+_Py_InitializeMain(void)
+{
+    _PyInitError err = _PyRuntime_Initialize();
+    if (_Py_INIT_FAILED(err)) {
+        return err;
+    }
+    _PyRuntimeState *runtime = &_PyRuntime;
+    PyInterpreterState *interp = _PyRuntimeState_GetThreadState(runtime)->interp;
+
+    return _Py_InitializeMainInterpreter(runtime, interp);
+}
+
+
 #undef _INIT_DEBUG_PRINT
 
 static _PyInitError
@@ -990,7 +1005,7 @@ init_python(const _PyCoreConfig *config, const _PyArgv *args)
     }
     config = &interp->core_config;
 
-    if (!config->_frozen) {
+    if (config->_init_main) {
         err = _Py_InitializeMainInterpreter(runtime, interp);
         if (_Py_INIT_FAILED(err)) {
             return err;