Bug #742342: make Python stop segfaulting on infinitely-recursive reload()s. Fixed by patch #922167.

Backported from r54291.

3 files changed, 41 insertions, 2 deletions

diff --git a/Python/import.c b/Python/import.c
index 390f9e3292..b62eeef768 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -339,6 +339,25 @@ imp_release_lock(PyObject *self, PyObject *noargs)
 	return Py_None;
 }
 
+PyObject *
+PyImport_GetModulesReloading(void)
+{
+	PyInterpreterState *interp = PyThreadState_Get()->interp;
+	if (interp->modules_reloading == NULL)
+		Py_FatalError("PyImport_GetModuleDict: no modules_reloading dictionary!");
+	return interp->modules_reloading;
+}
+
+static void
+imp_modules_reloading_clear (void)
+{
+	PyInterpreterState *interp = PyThreadState_Get()->interp;
+	if (interp->modules_reloading == NULL)
+		return;
+	PyDict_Clear(interp->modules_reloading);
+	return;
+}
+
 /* Helper for sys */
 
 PyObject *
@@ -498,6 +517,7 @@ PyImport_Cleanup(void)
 	PyDict_Clear(modules);
 	interp->modules = NULL;
 	Py_DECREF(modules);
+	Py_CLEAR(interp->modules_reloading);
 }
 
 
@@ -2400,8 +2420,9 @@ import_submodule(PyObject *mod, char *subname, char *fullname)
 PyObject *
 PyImport_ReloadModule(PyObject *m)
 {
+	PyObject *modules_reloading = PyImport_GetModulesReloading();
 	PyObject *modules = PyImport_GetModuleDict();
-	PyObject *path = NULL, *loader = NULL;
+	PyObject *path = NULL, *loader = NULL, *existing_m = NULL;
 	char *name, *subname;
 	char buf[MAXPATHLEN+1];
 	struct filedescr *fdp;
@@ -2422,20 +2443,30 @@ PyImport_ReloadModule(PyObject *m)
 			     name);
 		return NULL;
 	}
+	if ((existing_m = PyDict_GetItemString(modules_reloading, name)) != NULL) {
+		/* Due to a recursive reload, this module is already being reloaded. */
+		Py_INCREF(existing_m);
+		return existing_m;
+	}
+ 	PyDict_SetItemString(modules_reloading, name, m);
+
 	subname = strrchr(name, '.');
 	if (subname == NULL)
 		subname = name;
 	else {
 		PyObject *parentname, *parent;
 		parentname = PyString_FromStringAndSize(name, (subname-name));
-		if (parentname == NULL)
+		if (parentname == NULL) {
+			imp_modules_reloading_clear();
 			return NULL;
+		}
 		parent = PyDict_GetItem(modules, parentname);
 		if (parent == NULL) {
 			PyErr_Format(PyExc_ImportError,
 			    "reload(): parent %.200s not in sys.modules",
 			    PyString_AS_STRING(parentname));
 			Py_DECREF(parentname);
+			imp_modules_reloading_clear();
 			return NULL;
 		}
 		Py_DECREF(parentname);
@@ -2450,6 +2481,7 @@ PyImport_ReloadModule(PyObject *m)
 
 	if (fdp == NULL) {
 		Py_XDECREF(loader);
+		imp_modules_reloading_clear();
 		return NULL;
 	}
 
@@ -2466,6 +2498,7 @@ PyImport_ReloadModule(PyObject *m)
 		 */
 		PyDict_SetItemString(modules, name, m);
 	}
+	imp_modules_reloading_clear();
 	return newm;
 }
 
diff --git a/Python/pystate.c b/Python/pystate.c
index cc25e3ed38..086789d355 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -68,6 +68,7 @@ PyInterpreterState_New(void)
 			Py_FatalError("Can't initialize threads for interpreter");
 #endif
 		interp->modules = NULL;
+		interp->modules_reloading = NULL;
 		interp->sysdict = NULL;
 		interp->builtins = NULL;
 		interp->tstate_head = NULL;
@@ -107,6 +108,7 @@ PyInterpreterState_Clear(PyInterpreterState *interp)
 	Py_CLEAR(interp->codec_search_cache);
 	Py_CLEAR(interp->codec_error_registry);
 	Py_CLEAR(interp->modules);
+	Py_CLEAR(interp->modules_reloading);
 	Py_CLEAR(interp->sysdict);
 	Py_CLEAR(interp->builtins);
 }
diff --git a/Python/pythonrun.c b/Python/pythonrun.c
index 3b5307c7fb..75241fe915 100644
--- a/Python/pythonrun.c
+++ b/Python/pythonrun.c
@@ -193,6 +193,9 @@ Py_InitializeEx(int install_sigs)
 	interp->modules = PyDict_New();
 	if (interp->modules == NULL)
 		Py_FatalError("Py_Initialize: can't make modules dictionary");
+	interp->modules_reloading = PyDict_New();
+	if (interp->modules_reloading == NULL)
+		Py_FatalError("Py_Initialize: can't make modules_reloading dictionary");
 
 #ifdef Py_USING_UNICODE
 	/* Init Unicode implementation; relies on the codec registry */
@@ -530,6 +533,7 @@ Py_NewInterpreter(void)
 	/* XXX The following is lax in error checking */
 
 	interp->modules = PyDict_New();
+	interp->modules_reloading = PyDict_New();
 
 	bimod = _PyImport_FindExtension("__builtin__", "__builtin__");
 	if (bimod != NULL) {