C++: Cache parsing of template ids

...in order to stop memory intensive parsing for invalid code.

Parsing the test data/snippet "hard" led to a memory consumption of
about 5.5MB and this could easily get up to hundreds/gigabytes by adding
some more "if_<bool_<true>,\n" lines. With the caching, we are at about
1.0MB, even if more lines are added.

The "memory consumption" was measured with valgrind-massif. The stated
numbers are the reported peaks.

Task-number: QTCREATORBUG-12890
Change-Id: Ie7eb00cfc7915552d29bb27410a6b13a486f486e
Reviewed-by: Erik Verbruggen <erik.verbruggen@theqtcompany.com>

src/libs/3rdparty/cplusplus/Parser.cpp

@@ -165,6 +165,7 @@ public:
         Expression,
         ExpressionList,
         ParameterDeclarationClause,
+        TemplateId,
         TypeId
     };
 
@@ -510,6 +511,7 @@ bool Parser::parseClassOrNamespaceName(NameAST *&node)
 bool Parser::parseTemplateId(NameAST *&node, unsigned template_token)
 {
     DEBUG_THIS_RULE();
+    CHECK_CACHE(ASTCache::TemplateId, NameAST);
 
     const unsigned start = cursor();
 
@@ -523,14 +525,17 @@ bool Parser::parseTemplateId(NameAST *&node, unsigned template_token)
             if (maybeSplitGreaterGreaterToken() || LA() == T_GREATER) {
                 ast->greater_token = consumeToken();
                 node = ast;
-                return true;
+                const bool result = true;
+                _astCache->insert(ASTCache::TemplateId, start, node, cursor(), result);
+                return result;
             }
         }
     }
 
+    const bool result = false;
+    _astCache->insert(ASTCache::TemplateId, start, 0, cursor(), result);
     rewind(start);
-
+    return result;
-    return false;
 }
 
 bool Parser::parseNestedNameSpecifier(NestedNameSpecifierListAST *&node,

tests/auto/cplusplus/ast/tst_ast.cpp

@@ -199,6 +199,7 @@ private slots:
     void unnamed_class();
     void unnamed_class_data();
     void expensiveExpression();
+    void invalidCode_data();
     void invalidCode();
 };
 
@@ -1857,13 +1858,66 @@ void tst_AST::expensiveExpression()
     QVERIFY(unit->ast());
 }
 
+void tst_AST::invalidCode_data()
+{
+    QTest::addColumn<QByteArray>("source");
+
+    typedef QByteArray _;
+    QTest::newRow("simple") <<
+        _("static inValidLine()\n");
+
+    QTest::newRow("hard") <<
+        _("typedef\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true>,\n"
+          "if_<bool_<true {}\n");
+}
+
 void tst_AST::invalidCode()
 {
-    const QByteArray invalidCode = "static inValidLine()\n"
+    QFETCH(QByteArray, source);
-                                   "class Foo {};\n";
 
-    QSharedPointer<TranslationUnit> unit(parse(invalidCode, TranslationUnit::ParseTranlationUnit,
+    source += "\nclass Foo {};\n";
-                                               false, false, false));
+    const QSharedPointer<TranslationUnit> unit(parse(source, TranslationUnit::ParseTranlationUnit,
+                                                     false, false, true));
+
+    // Check that we find the class coming after the invalid garbage.
     QVERIFY(unit->ast());
     TranslationUnitAST *unitAST = unit->ast()->asTranslationUnit();
     QVERIFY(unitAST->declaration_list);