bpo-35454: Fix miscellaneous minor issues in error handling. (GH-11077)

* bpo-35454: Fix miscellaneous minor issues in error handling.

* Fix a null pointer dereference.
(cherry picked from commit 8905fcc85a6fc3ac394bc89b0bbf40897e9497a6)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

5 files changed, 18 insertions, 6 deletions

diff --git a/Python/_warnings.c b/Python/_warnings.c
index 29e475d67d..80dca65fd3 100644
--- a/Python/_warnings.c
+++ b/Python/_warnings.c
@@ -256,7 +256,11 @@ already_warned(PyObject *registry, PyObject *key, int should_set)
     version_obj = _PyDict_GetItemId(registry, &PyId_version);
     if (version_obj == NULL
         || !PyLong_CheckExact(version_obj)
-        || PyLong_AsLong(version_obj) != _PyRuntime.warnings.filters_version) {
+        || PyLong_AsLong(version_obj) != _PyRuntime.warnings.filters_version)
+    {
+        if (PyErr_Occurred()) {
+            return -1;
+        }
         PyDict_Clear(registry);
         version_obj = PyLong_FromLong(_PyRuntime.warnings.filters_version);
         if (version_obj == NULL)
diff --git a/Python/ceval.c b/Python/ceval.c
index e371d345cc..00b2e6d85f 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -5027,7 +5027,7 @@ unicode_concatenate(PyObject *v, PyObject *w,
             PyObject *names = f->f_code->co_names;
             PyObject *name = GETITEM(names, oparg);
             PyObject *locals = f->f_locals;
-            if (PyDict_CheckExact(locals) &&
+            if (locals && PyDict_CheckExact(locals) &&
                 PyDict_GetItem(locals, name) == v) {
                 if (PyDict_DelItem(locals, name) != 0) {
                     PyErr_Clear();
diff --git a/Python/codecs.c b/Python/codecs.c
index eb3cd35fb8..c315ae3ed7 100644
--- a/Python/codecs.c
+++ b/Python/codecs.c
@@ -130,8 +130,10 @@ PyObject *_PyCodec_Lookup(const char *encoding)
 
     /* Next, scan the search functions in order of registration */
     args = PyTuple_New(1);
-    if (args == NULL)
-        goto onError;
+    if (args == NULL) {
+        Py_DECREF(v);
+        return NULL;
+    }
     PyTuple_SET_ITEM(args,0,v);
 
     len = PyList_Size(interp->codec_search_path);
diff --git a/Python/import.c b/Python/import.c
index 709fc4324e..5f5d135c7a 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -2138,10 +2138,10 @@ _imp_create_dynamic_impl(PyObject *module, PyObject *spec, PyObject *file)
     }
 
     mod = _PyImport_FindExtensionObject(name, path);
-    if (mod != NULL) {
+    if (mod != NULL || PyErr_Occurred()) {
         Py_DECREF(name);
         Py_DECREF(path);
-        Py_INCREF(mod);
+        Py_XINCREF(mod);
         return mod;
     }
 
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index 4b08c9c2b2..94b6d43c0e 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -1417,6 +1417,9 @@ new_interpreter(PyThreadState **tstate_p)
         PyDict_SetItemString(interp->sysdict, "modules", modules);
         _PySys_EndInit(interp->sysdict, &interp->config);
     }
+    else if (PyErr_Occurred()) {
+        goto handle_error;
+    }
 
     bimod = _PyImport_FindBuiltin("builtins", modules);
     if (bimod != NULL) {
@@ -1425,6 +1428,9 @@ new_interpreter(PyThreadState **tstate_p)
             goto handle_error;
         Py_INCREF(interp->builtins);
     }
+    else if (PyErr_Occurred()) {
+        goto handle_error;
+    }
 
     /* initialize builtin exceptions */
     _PyExc_Init(bimod);