Issue #15001: fix segfault on "del sys.modules['__main__']"

Patch by Victor Stinner.

Lib/test/test_cmd_line.py

@@ -2,9 +2,12 @@
 # All tests are executed with environment variables ignored
 # See test_cmd_line_script.py for testing of script execution
 
-import test.test_support, unittest
+import test.test_support
 import sys
-from test.script_helper import spawn_python, kill_python, python_exit_code
+import unittest
+from test.script_helper import (
+    assert_python_ok, spawn_python, kill_python, python_exit_code
+)
 
 
 class CmdLineTest(unittest.TestCase):
@@ -101,6 +104,18 @@ class CmdLineTest(unittest.TestCase):
         data = self.start_python('-R', '-c', code)
         self.assertTrue('hash_randomization=1' in data)
 
+    def test_del___main__(self):
+        # Issue #15001: PyRun_SimpleFileExFlags() did crash because it kept a
+        # borrowed reference to the dict of __main__ module and later modify
+        # the dict whereas the module was destroyed
+        filename = test.test_support.TESTFN
+        self.addCleanup(test.test_support.unlink, filename)
+        with open(filename, "w") as script:
+            print >>script, "import sys"
+            print >>script, "del sys.modules['__main__']"
+        assert_python_ok(filename)
+
+
 def test_main():
     test.test_support.run_unittest(CmdLineTest)
     test.test_support.reap_children()

Misc/NEWS

@@ -9,6 +9,9 @@ What's New in Python 2.7.4
 Core and Builtins
 -----------------
 
+- Issue #15001: fix segfault on "del sys.modules['__main__']". Patch by Victor
+  Stinner.
+
 - Issue #5057: the peepholer no longer optimizes subscription on unicode
   literals (e.g. u'foo'[0]) in order to produce compatible pyc files between
   narrow and wide builds.

Python/pythonrun.c

@@ -907,19 +907,20 @@ PyRun_SimpleFileExFlags(FILE *fp, const char *filename, int closeit,
 {
     PyObject *m, *d, *v;
     const char *ext;
-    int set_file_name = 0, ret, len;
+    int set_file_name = 0, len, ret = -1;
 
     m = PyImport_AddModule("__main__");
     if (m == NULL)
         return -1;
+    Py_INCREF(m);
     d = PyModule_GetDict(m);
     if (PyDict_GetItemString(d, "__file__") == NULL) {
         PyObject *f = PyString_FromString(filename);
         if (f == NULL)
-            return -1;
+            goto done;
         if (PyDict_SetItemString(d, "__file__", f) < 0) {
             Py_DECREF(f);
-            return -1;
+            goto done;
         }
         set_file_name = 1;
         Py_DECREF(f);
@@ -932,7 +933,6 @@ PyRun_SimpleFileExFlags(FILE *fp, const char *filename, int closeit,
             fclose(fp);
         if ((fp = fopen(filename, "rb")) == NULL) {
             fprintf(stderr, "python: Can't reopen .pyc file\n");
-            ret = -1;
             goto done;
         }
         /* Turn on optimization if a .pyo file is given */
@@ -945,7 +945,6 @@ PyRun_SimpleFileExFlags(FILE *fp, const char *filename, int closeit,
     }
     if (v == NULL) {
         PyErr_Print();
-        ret = -1;
         goto done;
     }
     Py_DECREF(v);
@@ -955,6 +954,7 @@ PyRun_SimpleFileExFlags(FILE *fp, const char *filename, int closeit,
   done:
     if (set_file_name && PyDict_DelItemString(d, "__file__"))
         PyErr_Clear();
+    Py_DECREF(m);
     return ret;
 }