bpo-36301: Add _PyRuntime.pre_initialized (GH-12457)

* Add _PyRuntime.pre_initialized: set to 1 when Python
  is pre-initialized
* Add _Py_PreInitialize() and _Py_PreInitializeFromPreConfig().
* _PyCoreConfig_Read() now calls  _Py_PreInitialize().
* Move _PyPreConfig_GetGlobalConfig() and
  _PyCoreConfig_GetGlobalConfig() calls from main.c to preconfig.c
  and coreconfig.c.

1 files changed, 42 insertions, 4 deletions

diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index df9570b..994a94f 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -714,19 +714,57 @@ _Py_InitializeCore_impl(PyInterpreterState **interp_p,
 }
 
 
+_PyInitError
+_Py_PreInitializeFromPreConfig(_PyPreConfig *config)
+{
+    if (config != NULL) {
+        _PyInitError err = _PyPreConfig_Write(config);
+        if (_Py_INIT_FAILED(err)) {
+            return err;
+        }
+    }
+
+    _PyRuntime.pre_initialized = 1;
+    return _Py_INIT_OK();
+}
+
+
 static _PyInitError
-pyinit_preconfig(_PyPreConfig *preconfig, const _PyPreConfig *src_preconfig)
+pyinit_preconfig(_PyPreConfig *config, const _PyPreConfig *src_config)
 {
-    if (_PyPreConfig_Copy(preconfig, src_preconfig) < 0) {
+    _PyInitError err;
+
+    err = _PyRuntime_Initialize();
+    if (_Py_INIT_FAILED(err)) {
+        return err;
+    }
+
+    if (_PyPreConfig_Copy(config, src_config) < 0) {
         return _Py_INIT_ERR("failed to copy pre config");
     }
 
-    _PyInitError err = _PyPreConfig_Read(preconfig);
+    err = _PyPreConfig_Read(config);
     if (_Py_INIT_FAILED(err)) {
         return err;
     }
 
-    return _PyPreConfig_Write(preconfig);
+    return _Py_PreInitializeFromPreConfig(config);
+}
+
+
+_PyInitError
+_Py_PreInitialize(void)
+{
+    _PyInitError err = _PyRuntime_Initialize();
+    if (_Py_INIT_FAILED(err)) {
+        return err;
+    }
+
+    if (_PyRuntime.pre_initialized) {
+        return _Py_INIT_OK();
+    }
+
+    return _Py_PreInitializeFromPreConfig(NULL);
 }