Fix libstdc++ data formatter for reference/pointer to std::string

[yinghuitan]

Summary

This patch fixes libstdc++ data formatter for reference/pointer to std::string.
The failure testcases are added which succeed with the patch.

[JDevlieghere]

I'm surprised this didn't work but was able to reproduce the failure on Linux with libstdcpp. LGTM.

lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.cpp

if (name == "item")
     return 0;
   return UINT32_MAX;
 }
 
 bool lldb_private::formatters::LibStdcppStringSummaryProvider(
     ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) {
   const bool scalar_is_load_addr = true;
   AddressType addr_type;
-  lldb::addr_t addr_of_string =
+  lldb::addr_t addr_of_string = LLDB_INVALID_ADDRESS;
+  if (valobj.IsPointerOrReferenceType()) {
+    Status error;
+    ValueObjectSP pointee_sp = valobj.Dereference(error);
+    if (pointee_sp && error.Success())
+      addr_of_string = pointee_sp->GetAddressOf(scalar_is_load_addr, &addr_type);
+  } else
+    addr_of_string =
         valobj.GetAddressOf(scalar_is_load_addr, &addr_type);
   if (addr_of_string != LLDB_INVALID_ADDRESS) {
     switch (addr_type) {
     case eAddressTypeLoad: {
       ProcessSP process_sp(valobj.GetProcessSP());
       if (!process_sp)
         return false;
 
       StringPrinter::ReadStringAndDumpToStreamOptions options(valobj);

lldb/test/API/functionalities/data-formatter/data-formatter-stl/libstdcpp/string/TestDataFormatterStdString.py

def test_with_run_command(self):
 
         var_wempty = self.frame().FindVariable('wempty')
         var_s = self.frame().FindVariable('s')
         var_S = self.frame().FindVariable('S')
         var_mazeltov = self.frame().FindVariable('mazeltov')
         var_empty = self.frame().FindVariable('empty')
         var_q = self.frame().FindVariable('q')
         var_Q = self.frame().FindVariable('Q')
+        var_rq = self.frame().FindVariable('rq')
+        var_rQ = self.frame().FindVariable('rQ')
+        var_pq = self.frame().FindVariable('pq')
+        var_pQ = self.frame().FindVariable('pQ')
+
         var_uchar = self.frame().FindVariable('uchar')
 
         self.assertEqual(var_wempty.GetSummary(), 'L""', "wempty summary wrong")
         self.assertEqual(
             var_s.GetSummary(), 'L"hello world! מזל טוב!"',
             "s summary wrong")
         self.assertEqual(var_S.GetSummary(), 'L"!!!!"', "S summary wrong")
         self.assertEqual(
             var_mazeltov.GetSummary(), 'L"מזל טוב"',
             "mazeltov summary wrong")
         self.assertEqual(var_empty.GetSummary(), '""', "empty summary wrong")
         self.assertEqual(
             var_q.GetSummary(), '"hello world"',
             "q summary wrong")
         self.assertEqual(
             var_Q.GetSummary(), '"quite a long std::strin with lots of info inside it"',
             "Q summary wrong")
         self.assertEqual(var_uchar.GetSummary(), '"aaaaa"', "u summary wrong")
+        self.assertEqual(
+            var_rq.GetSummary(), '"hello world"',
+            "rq summary wrong")
+        self.assertEqual(
+            var_rQ.GetSummary(), '"quite a long std::strin with lots of info inside it"',
+            "rQ summary wrong")
+        self.assertEqual(
+            var_pq.GetSummary(), '"hello world"',
+            "pq summary wrong")
+        self.assertEqual(
+            var_pQ.GetSummary(), '"quite a long std::strin with lots of info inside it"',
+            "pQ summary wrong")
 
         self.runCmd("next")
 
         self.assertEqual(
             var_S.GetSummary(), 'L"!!!!!"',
             "new S summary wrong")

lldb/test/API/functionalities/data-formatter/data-formatter-stl/libstdcpp/string/main.cpp

 #include <string>
 
 int main()
 {
     std::wstring wempty(L"");
     std::wstring s(L"hello world! מזל טוב!");
     std::wstring S(L"!!!!");
     const wchar_t *mazeltov = L"מזל טוב";
     std::string empty("");
     std::string q("hello world");
     std::string Q("quite a long std::strin with lots of info inside it");
     std::basic_string<unsigned char> uchar(5, 'a');
+    auto &rq = q, &rQ = Q;
+    std::string *pq = &q, *pQ = &Q;
     S.assign(L"!!!!!"); // Set break point at this line.
     return 0;
 }