bpo-42260: Add _PyInterpreterState_SetConfig() (GH-23158)

* Inline _PyInterpreterState_SetConfig(): replace it with
  _PyConfig_Copy().
* Add _PyErr_SetFromPyStatus()
* Add _PyInterpreterState_GetConfigCopy()
* Add a new _PyInterpreterState_SetConfig() function.
* Add an unit which gets, modifies, and sets the config.

3 files changed, 96 insertions, 10 deletions

diff --git a/Python/initconfig.c b/Python/initconfig.c
index 15fb3e4..de496ac 100644
--- a/Python/initconfig.c
+++ b/Python/initconfig.c
@@ -242,8 +242,9 @@ PyStatus PyStatus_Ok(void)
 
 PyStatus PyStatus_Error(const char *err_msg)
 {
+    assert(err_msg != NULL);
     return (PyStatus){._type = _PyStatus_TYPE_ERROR,
-                          .err_msg = err_msg};
+                      .err_msg = err_msg};
 }
 
 PyStatus PyStatus_NoMemory(void)
@@ -262,6 +263,23 @@ int PyStatus_IsExit(PyStatus status)
 int PyStatus_Exception(PyStatus status)
 { return _PyStatus_EXCEPTION(status); }
 
+PyObject*
+_PyErr_SetFromPyStatus(PyStatus status)
+{
+    if (!_PyStatus_IS_ERROR(status)) {
+        PyErr_Format(PyExc_SystemError,
+                     "%s() expects an error PyStatus",
+                     _PyStatus_GET_FUNC());
+    }
+    else if (status.func) {
+        PyErr_Format(PyExc_ValueError, "%s: %s", status.func, status.err_msg);
+    }
+    else {
+        PyErr_Format(PyExc_ValueError, "%s", status.err_msg);
+    }
+    return NULL;
+}
+
 
 /* --- PyWideStringList ------------------------------------------------ */
 
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index 1f826d7..e34d647 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -428,6 +428,67 @@ _Py_SetLocaleFromEnv(int category)
 }
 
 
+static int
+interpreter_set_config(const PyConfig *config)
+{
+    PyThreadState *tstate = PyThreadState_Get();
+
+    PyStatus status = _PyConfig_Write(config, tstate->interp->runtime);
+    if (_PyStatus_EXCEPTION(status)) {
+        _PyErr_SetFromPyStatus(status);
+        return -1;
+    }
+
+    status = _PyConfig_Copy(&tstate->interp->config, config);
+    if (_PyStatus_EXCEPTION(status)) {
+        _PyErr_SetFromPyStatus(status);
+        return -1;
+    }
+    config = &tstate->interp->config;
+
+    if (config->_install_importlib && _Py_IsMainInterpreter(tstate)) {
+        status = _PyConfig_WritePathConfig(config);
+        if (_PyStatus_EXCEPTION(status)) {
+            _PyErr_SetFromPyStatus(status);
+            return -1;
+        }
+    }
+
+    // Update the sys module for the new configuration
+    if (_PySys_UpdateConfig(tstate) < 0) {
+        return -1;
+    }
+    return 0;
+}
+
+
+int
+_PyInterpreterState_SetConfig(const PyConfig *src_config)
+{
+    int res = -1;
+
+    PyConfig config;
+    PyConfig_InitPythonConfig(&config);
+    PyStatus status = _PyConfig_Copy(&config, src_config);
+    if (_PyStatus_EXCEPTION(status)) {
+        _PyErr_SetFromPyStatus(status);
+        goto done;
+    }
+
+    status = PyConfig_Read(&config);
+    if (_PyStatus_EXCEPTION(status)) {
+        _PyErr_SetFromPyStatus(status);
+        goto done;
+    }
+
+    res = interpreter_set_config(&config);
+
+done:
+    PyConfig_Clear(&config);
+    return res;
+}
+
+
 /* Global initializations.  Can be undone by Py_Finalize().  Don't
    call this twice without an intervening Py_Finalize() call.
 
@@ -462,7 +523,7 @@ pyinit_core_reconfigure(_PyRuntimeState *runtime,
         return status;
     }
 
-    status = _PyInterpreterState_SetConfig(interp, config);
+    status = _PyConfig_Copy(&interp->config, config);
     if (_PyStatus_EXCEPTION(status)) {
         return status;
     }
@@ -550,7 +611,7 @@ pycore_create_interpreter(_PyRuntimeState *runtime,
         return _PyStatus_ERR("can't make main interpreter");
     }
 
-    PyStatus status = _PyInterpreterState_SetConfig(interp, config);
+    PyStatus status = _PyConfig_Copy(&interp->config, config);
     if (_PyStatus_EXCEPTION(status)) {
         return status;
     }
@@ -917,7 +978,7 @@ pyinit_core(_PyRuntimeState *runtime,
     }
 
     PyConfig config;
-    _PyConfig_InitCompatConfig(&config);
+    PyConfig_InitPythonConfig(&config);
 
     status = _PyConfig_Copy(&config, src_config);
     if (_PyStatus_EXCEPTION(status)) {
@@ -1835,7 +1896,8 @@ new_interpreter(PyThreadState **tstate_p, int isolated_subinterpreter)
         config = _PyInterpreterState_GetConfig(main_interp);
     }
 
-    status = _PyInterpreterState_SetConfig(interp, config);
+
+    status = _PyConfig_Copy(&interp->config, config);
     if (_PyStatus_EXCEPTION(status)) {
         goto error;
     }
diff --git a/Python/pystate.c b/Python/pystate.c
index c9882a7..600cc5e 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -778,7 +778,7 @@ PyState_RemoveModule(struct PyModuleDef* def)
     return PyList_SetItem(interp->modules_by_index, index, Py_None);
 }
 
-/* Used by PyImport_Cleanup() */
+// Used by finalize_modules()
 void
 _PyInterpreterState_ClearModules(PyInterpreterState *interp)
 {
@@ -1920,11 +1920,17 @@ _PyInterpreterState_GetConfig(PyInterpreterState *interp)
 }
 
 
-PyStatus
-_PyInterpreterState_SetConfig(PyInterpreterState *interp,
-                              const PyConfig *config)
+int
+_PyInterpreterState_GetConfigCopy(PyConfig *config)
 {
-    return _PyConfig_Copy(&interp->config, config);
+    PyInterpreterState *interp = PyInterpreterState_Get();
+
+    PyStatus status = _PyConfig_Copy(config, &interp->config);
+    if (PyStatus_Exception(status)) {
+        _PyErr_SetFromPyStatus(status);
+        return -1;
+    }
+    return 0;
 }