Add logic to SBValue.linked_list_iter() to detect infinite loop and to bail out early.

Add code to test case to create an evil linked list with:

    task_evil -> task_2 -> task_3 -> task_evil ...

and to check that the linked list iterator only iterates 3 times.

llvm-svn: 137291

lldb/scripts/Python/modify-python-lldb.py

@@ -112,6 +112,8 @@ linked_list_iter_def = '''
         end-of-list test function which takes an SBValue for an item and returns
         True if EOL is reached and False if not.
 
+        linked_list_iter() also detects infinite loop and bails out early.
+
         The end_of_list_test arg, if omitted, defaults to the __eol_test__
         function above.
 
@@ -130,8 +132,10 @@ linked_list_iter_def = '''
         if end_of_list_test(self):
             return
         item = self
+        visited = set()
         try:
-            while not end_of_list_test(item):
+            while not end_of_list_test(item) and not item.GetValueAsUnsigned() in visited:
+                visited.add(item.GetValueAsUnsigned())
                 yield item
                 # Prepare for the next iteration.
                 item = item.GetChildMemberWithName(next_item_name)

lldb/test/python_api/value/linked_list/TestValueAPILinkedList.py

@@ -127,6 +127,20 @@ class ValueAsLinkedListTestCase(TestBase):
 
         self.assertTrue(len(list) == 0)
 
+        # Get variable 'task_evil'.
+        task_evil = frame0.FindVariable('task_evil')
+        self.assertTrue(task_evil, VALID_VARIABLE)
+        self.DebugSBValue(task_evil)
+
+        list = []
+        # There 3 iterable items from task_evil.linked_list_iter(). :-)
+        for t in task_evil.linked_list_iter('next'):
+            if self.TraceOn():
+                print cvf.format(t)
+            list.append(int(t.GetChildMemberWithName("id").GetValue()))
+
+        self.assertTrue(len(list) == 3)
+
 if __name__ == '__main__':
     import atexit
     lldb.SBDebugger.Initialize()

lldb/test/python_api/value/linked_list/main.cpp

@@ -45,5 +45,12 @@ int main (int argc, char const *argv[])
     // This corresponds to an empty task list.
     Task *empty_task_head = NULL;
 
+    Task *task_evil = new Task(1, NULL);
+    Task *task_2 = new Task(2, NULL);
+    Task *task_3 = new Task(3, NULL);
+    task_evil->next = task_2;
+    task_2->next = task_3;
+    task_3->next = task_evil; // In order to cause inifinite loop. :-)
+
     return 0; // Break at this line
 }