[demangler] Fix another bug found by oss-fuzz in r309340

llvm-svn: 309650

libcxxabi/src/cxa_demangle.cpp

@@ -5867,6 +5867,8 @@ parse_encoding(const char* first, const char* last, Db& db)
                     if (t != last && *t == 'v')
                     {
                         ++t;
+                        if (db.names.empty())
+                            return first;
                         Node* name = db.names.back();
                         db.names.pop_back();
                         result = db.make<TopLevelFunctionDecl>(

libcxxabi/test/test_demangle.pass.cpp

@@ -29676,6 +29676,7 @@ const char* invalid_cases[] =
     "AT__ZSiIJEEAnwscT_T__",
     "FSiIJEENT_IoE ",
     "ZTVSiIZTVSiIZTVSiIZTVSiINIJEET_T_T_T_T_ ",
+    "_ZSiIJEvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvttvvvvvvET_v",
 };
 
 const unsigned NI = sizeof(invalid_cases) / sizeof(invalid_cases[0]);