Adjusting libc++ std::list formatter to act better with pointers and references and adding a test to cover a previous related fix

[shafik]

Summary

This previous fix https://github.com/llvm-mirror/lldb/commit/5469bda296c183d1b6bf74597c88c9ed667b3145 did not have a test since we did not have a reproducer.

This is related to how formatters deal with pointers and references. The added tests both the new behavior and covers the previous bug fix as well.

[jingham]

LGTM

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/list/TestDataFormatterLibcxxList.py

def test_with_run_command(self):
 
         self.expect("frame variable numbers_list",
                     substrs=['list has 4 items',
                              '[0] = ', '1',
                              '[1] = ', '2',
                              '[2] = ', '3',
                              '[3] = ', '4'])
 
+        ListPtr = self.frame().FindVariable("list_ptr")
+        self.assertTrue(ListPtr.GetChildAtIndex(
+            0).GetValueAsUnsigned(0) == 1, "[0] = 1")
+
         # check that MightHaveChildren() gets it right
         self.assertTrue(
             self.frame().FindVariable("numbers_list").MightHaveChildren(),
             "numbers_list.MightHaveChildren() says False for non empty!")
 
         self.runCmd("type format delete int")
 
         self.runCmd("c")

packages/Python/lldbsuite/test/functionalities/data-formatter/data-formatter-stl/libcxx/list/main.cpp

 #include <string>
 #include <list>
 #include <stdio.h>
 
 typedef std::list<int> int_list;
 typedef std::list<std::string> string_list;
 
 int main()
 {
     int_list numbers_list;
-    
+    std::list<int>* list_ptr = &numbers_list;
     printf("// Set break point at this line.");
     (numbers_list.push_back(0x12345678));
     (numbers_list.push_back(0x11223344));
     (numbers_list.push_back(0xBEEFFEED));
     (numbers_list.push_back(0x00ABBA00));
     (numbers_list.push_back(0x0ABCDEF0));
     (numbers_list.push_back(0x0CAB0CAB));
     

source/Plugins/Language/CPlusPlus/CPlusPlusLanguage.cpp

AddCXXSynthetic(
       lldb_private::formatters::LibcxxStdForwardListSyntheticFrontEndCreator,
       "libc++ std::forward_list synthetic children",
       ConstString("^std::__[[:alnum:]]+::forward_list<.+>(( )?&)?$"),
       stl_synth_flags, true);
   AddCXXSynthetic(
       cpp_category_sp,
       lldb_private::formatters::LibcxxStdListSyntheticFrontEndCreator,
       "libc++ std::list synthetic children",
-      ConstString("^std::__[[:alnum:]]+::list<.+>(( )?&)?$"), stl_synth_flags,
+      ConstString("^std::__[[:alnum:]]+::list<.+>(( )?&)?$"), stl_deref_flags,
       true);
   AddCXXSynthetic(
       cpp_category_sp,
       lldb_private::formatters::LibcxxStdMapSyntheticFrontEndCreator,
       "libc++ std::map synthetic children",
       ConstString("^std::__[[:alnum:]]+::map<.+> >(( )?&)?$"), stl_synth_flags,
       true);
   AddCXXSynthetic(