1 files changed, 55 insertions, 13 deletions

diff --git a/Python/import.c b/Python/import.c
index 0b843dafd3..22f94f5f18 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -320,7 +320,7 @@ PyImport_GetModuleDict(void)
 
 
 /* List of names to clear in sys */
-static char* sys_deletes[] = {
+static const char * const sys_deletes[] = {
     "path", "argv", "ps1", "ps2",
     "last_type", "last_value", "last_traceback",
     "path_hooks", "path_importer_cache", "meta_path",
@@ -330,7 +330,7 @@ static char* sys_deletes[] = {
     NULL
 };
 
-static char* sys_files[] = {
+static const char * const sys_files[] = {
     "stdin", "__stdin__",
     "stdout", "__stdout__",
     "stderr", "__stderr__",
@@ -347,7 +347,7 @@ PyImport_Cleanup(void)
     PyInterpreterState *interp = PyThreadState_GET()->interp;
     PyObject *modules = interp->modules;
     PyObject *weaklist = NULL;
-    char **p;
+    const char * const *p;
 
     if (modules == NULL)
         return; /* Already done */
@@ -883,10 +883,8 @@ update_code_filenames(PyCodeObject *co, PyObject *oldname, PyObject *newname)
     if (PyUnicode_Compare(co->co_filename, oldname))
         return;
 
-    tmp = co->co_filename;
-    co->co_filename = newname;
-    Py_INCREF(co->co_filename);
-    Py_DECREF(tmp);
+    Py_INCREF(newname);
+    Py_SETREF(co->co_filename, newname);
 
     constants = co->co_consts;
     n = PyTuple_GET_SIZE(constants);
@@ -1331,10 +1329,8 @@ remove_importlib_frames(void)
             (always_trim ||
              PyUnicode_CompareWithASCIIString(code->co_name,
                                               remove_frames) == 0)) {
-            PyObject *tmp = *outer_link;
-            *outer_link = next;
             Py_XINCREF(next);
-            Py_DECREF(tmp);
+            Py_SETREF(*outer_link, next);
             prev_link = outer_link;
         }
         else {
@@ -1367,6 +1363,7 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *given_globals,
     PyObject *final_mod = NULL;
     PyObject *mod = NULL;
     PyObject *package = NULL;
+    PyObject *spec = NULL;
     PyObject *globals = NULL;
     PyObject *fromlist = NULL;
     PyInterpreterState *interp = PyThreadState_GET()->interp;
@@ -1423,23 +1420,63 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *given_globals,
     }
     else if (level > 0) {
         package = _PyDict_GetItemId(globals, &PyId___package__);
+        spec = _PyDict_GetItemId(globals, &PyId___spec__);
+
         if (package != NULL && package != Py_None) {
             Py_INCREF(package);
             if (!PyUnicode_Check(package)) {
                 PyErr_SetString(PyExc_TypeError, "package must be a string");
                 goto error;
             }
+            else if (spec != NULL && spec != Py_None) {
+                int equal;
+                PyObject *parent = PyObject_GetAttrString(spec, "parent");
+                if (parent == NULL) {
+                    goto error;
+                }
+
+                equal = PyObject_RichCompareBool(package, parent, Py_EQ);
+                Py_DECREF(parent);
+                if (equal < 0) {
+                    goto error;
+                }
+                else if (equal == 0) {
+                    if (PyErr_WarnEx(PyExc_ImportWarning,
+                            "__package__ != __spec__.parent", 1) < 0) {
+                        goto error;
+                    }
+                }
+            }
+        }
+        else if (spec != NULL && spec != Py_None) {
+            package = PyObject_GetAttrString(spec, "parent");
+            if (package == NULL) {
+                goto error;
+            }
+            else if (!PyUnicode_Check(package)) {
+                PyErr_SetString(PyExc_TypeError,
+                        "__spec__.parent must be a string");
+                goto error;
+            }
         }
         else {
+            if (PyErr_WarnEx(PyExc_ImportWarning,
+                        "can't resolve package from __spec__ or __package__, "
+                        "falling back on __name__ and __path__", 1) < 0) {
+                goto error;
+            }
+
             package = _PyDict_GetItemId(globals, &PyId___name__);
             if (package == NULL) {
                 PyErr_SetString(PyExc_KeyError, "'__name__' not in globals");
                 goto error;
             }
-            else if (!PyUnicode_Check(package)) {
+
+            Py_INCREF(package);
+            if (!PyUnicode_Check(package)) {
                 PyErr_SetString(PyExc_TypeError, "__name__ must be a string");
+                goto error;
             }
-            Py_INCREF(package);
 
             if (_PyDict_GetItemId(globals, &PyId___path__) == NULL) {
                 PyObject *partition = NULL;
@@ -1458,7 +1495,12 @@ PyImport_ImportModuleLevelObject(PyObject *name, PyObject *given_globals,
             }
         }
 
-        if (PyDict_GetItem(interp->modules, package) == NULL) {
+        if (PyUnicode_CompareWithASCIIString(package, "") == 0) {
+            PyErr_SetString(PyExc_ImportError,
+                    "attempted relative import with no known parent package");
+            goto error;
+        }
+        else if (PyDict_GetItem(interp->modules, package) == NULL) {
             PyErr_Format(PyExc_SystemError,
                     "Parent module %R not loaded, cannot perform relative "
                     "import", package);