Index: lldb/trunk/packages/Python/lldbsuite/test/functionalities/completion/TestCompletion.py
===================================================================
--- lldb/trunk/packages/Python/lldbsuite/test/functionalities/completion/TestCompletion.py
+++ lldb/trunk/packages/Python/lldbsuite/test/functionalities/completion/TestCompletion.py
@@ -297,3 +297,6 @@
         self.complete_from_to('breakpoint set -n Fo',
                               'breakpoint set -n Foo::Bar(int,\\ int)',
                               turn_off_re_match=True)
+        # No completion for Qu because the candidate is
+        # (anonymous namespace)::Quux().
+        self.complete_from_to('breakpoint set -n Qu', '')
Index: lldb/trunk/packages/Python/lldbsuite/test/functionalities/completion/main.cpp
===================================================================
--- lldb/trunk/packages/Python/lldbsuite/test/functionalities/completion/main.cpp
+++ lldb/trunk/packages/Python/lldbsuite/test/functionalities/completion/main.cpp
@@ -7,6 +7,8 @@
     }
 };
 
+namespace { int Quux (void) { return 0; } }
+
 struct Container { int MemberVar; };
 
 int main()
@@ -17,5 +19,6 @@
 
     Container container;
     Container *ptr_container = &container;
+    int q = Quux();
     return container.MemberVar = 3; // Break here
 }
Index: lldb/trunk/source/Commands/CommandCompletions.cpp
===================================================================
--- lldb/trunk/source/Commands/CommandCompletions.cpp
+++ lldb/trunk/source/Commands/CommandCompletions.cpp
@@ -471,7 +471,11 @@
     for (uint32_t i = 0; i < sc_list.GetSize(); i++) {
       if (sc_list.GetContextAtIndex(i, sc)) {
         ConstString func_name = sc.GetFunctionName(Mangled::ePreferDemangled);
-        if (!func_name.IsEmpty())
+        // Ensure that the function name matches the regex. This is more than a
+        // sanity check. It is possible that the demangled function name does
+        // not start with the prefix, for example when it's in an anonymous
+        // namespace.
+        if (!func_name.IsEmpty() && m_regex.Execute(func_name.GetStringRef()))
           m_match_set.insert(func_name);
       }
     }