From 0bcddcd0140f9daf54ba0b74b4afc3736c225fe0 Mon Sep 17 00:00:00 2001
From: Orgad Shaneh <orgad.shaneh@audiocodes.com>
Date: Wed, 11 Nov 2015 23:13:19 +0200
Subject: [PATCH] C++: Limit template instantiation depth

A recursive template generates infinite expansions.

Consider the following example:

template <class R1>
struct Base
{
};

template<typename R>
struct Derived :
  Base<
    typename Derived<typename Base<R>::type>::type,
    typename Derived<typename Base<R>::type>::type
  >::type
{};

R is instantiated as Base<R>::type, which causes another
instantiation of R into Base<Base<R>> etc...

This is not a solution, but a workaround.

Task-number: QTCREATORBUG-15141
Change-Id: Ib04f70275e07919e2cb6c7fb61a2045bd52f4a7d
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@theqtcompany.com>
---
 src/libs/cplusplus/LookupContext.cpp          |  6 ++++++
 src/libs/cplusplus/LookupContext.h            |  1 +
 .../checksymbols/tst_checksymbols.cpp         | 21 +++++++++++++++++++
 3 files changed, 28 insertions(+)

diff --git a/src/libs/cplusplus/LookupContext.cpp b/src/libs/cplusplus/LookupContext.cpp
index 0364b59c725..401d54f48b3 100644
--- a/src/libs/cplusplus/LookupContext.cpp
+++ b/src/libs/cplusplus/LookupContext.cpp
@@ -1549,6 +1549,7 @@ CreateBindings::CreateBindings(Document::Ptr thisDocument, const Snapshot &snaps
     : _snapshot(snapshot)
     , _control(QSharedPointer<Control>(new Control))
     , _expandTemplates(false)
+    , _depth(0)
 {
     _globalNamespace = allocLookupScope(/*parent = */ 0, /*name = */ 0);
     _currentLookupScope = _globalNamespace;
@@ -1978,8 +1979,13 @@ void CreateBindings::initializeSubst(Clone &cloner,
 {
     const unsigned argumentCountOfSpecialization = specialization->templateParameterCount();
 
+    if (_depth > 15)
+        return;
+
+    ++_depth;
     for (unsigned i = 0; i < argumentCountOfSpecialization; ++i)
         resolveTemplateArgument(cloner, subst, origin, specialization, instantiation, i);
+    --_depth;
 }
 
 } // namespace CPlusPlus
diff --git a/src/libs/cplusplus/LookupContext.h b/src/libs/cplusplus/LookupContext.h
index 8d4016dbbbb..8410c9000b7 100644
--- a/src/libs/cplusplus/LookupContext.h
+++ b/src/libs/cplusplus/LookupContext.h
@@ -209,6 +209,7 @@ private:
     LookupScope *_globalNamespace;
     LookupScope *_currentLookupScope;
     bool _expandTemplates;
+    int _depth;
 };
 
 class CPLUSPLUS_EXPORT LookupContext
diff --git a/tests/auto/cplusplus/checksymbols/tst_checksymbols.cpp b/tests/auto/cplusplus/checksymbols/tst_checksymbols.cpp
index a04cdd16658..3b16861c8b1 100644
--- a/tests/auto/cplusplus/checksymbols/tst_checksymbols.cpp
+++ b/tests/auto/cplusplus/checksymbols/tst_checksymbols.cpp
@@ -225,6 +225,8 @@ private slots:
     void test_checksymbols_infiniteLoop_data();
     void test_checksymbols_infiniteLoop();
 
+    void test_checksymbols_infiniteLoop_BUG15141();
+
     void test_parentOfBlock();
 
     void findField();
@@ -1122,6 +1124,25 @@ void tst_CheckSymbols::test_checksymbols_infiniteLoop()
     TestCase::runCheckSymbols(document1, snapshot);
 }
 
+void tst_CheckSymbols::test_checksymbols_infiniteLoop_BUG15141()
+{
+    QByteArray source =
+            "template <class R1>\n"
+            "struct Base\n"
+            "{\n"
+            "};\n"
+            "\n"
+            "template<typename R>\n"
+            "struct Derived :\n"
+            "  Base<\n"
+            "    typename Derived<typename Base<R>::type>::type,\n"
+            "    typename Derived<typename Base<R>::type>::type\n"
+            "  >::type\n"
+            "{};\n";
+
+    BaseTestCase tc(source);
+}
+
 void tst_CheckSymbols::test_parentOfBlock()
 {
     const QByteArray source = "void C::f()\n"