The SBValue.linked_list_iter() API failed for an empty list.

Fix the bug and add a test case.

llvm-svn: 136265

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

@@ -91,6 +91,10 @@ class ValueAsLinkedListTestCase(TestBase):
             # or it corresponds to a null pointer.
             if not val or int(val.GetValue(), 16) == 0:
                 return True
+            # Also check the "id" for correct semantics.  If id <= 0, the item
+            # is corrupted, let's return True to signify end of list.
+            if int(val.GetChildMemberWithName("id").GetValue(), 0) <= 0:
+                return True
 
             # Otherwise, return False.
             return False
@@ -109,6 +113,20 @@ class ValueAsLinkedListTestCase(TestBase):
             print "visited IDs:", list
         self.assertTrue(visitedIDs == list)
         
+        # Get variable 'empty_task_head'.
+        empty_task_head = frame0.FindVariable('empty_task_head')
+        self.assertTrue(empty_task_head, VALID_VARIABLE)
+        self.DebugSBValue(empty_task_head)
+
+        list = []
+        # There is no iterable item from empty_task_head.linked_list_iter().
+        for t in empty_task_head.linked_list_iter('next', eol):
+            if self.TraceOn():
+                print cvf.format(t)
+            list.append(int(t.GetChildMemberWithName("id").GetValue()))
+
+        self.assertTrue(len(list) == 0)
+
 if __name__ == '__main__':
     import atexit
     lldb.SBDebugger.Initialize()

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

@@ -33,7 +33,7 @@ int main (int argc, char const *argv[])
     task2->next = task4;
     task4->next = task5;
 
-    int total = 0; // Break at this line
+    int total = 0;
     Task *t = task_head;
     while (t != NULL) {
         if (t->id >= 0)
@@ -41,5 +41,9 @@ int main (int argc, char const *argv[])
         t = t->next;
     }
     printf("We have a total number of %d tasks\n", total);
-    return 0;
+
+    // This corresponds to an empty task list.
+    Task *empty_task_head = new Task(-1, NULL);
+
+    return 0; // Break at this line
 }