https://gcc.gnu.org/bugzilla/show_bug.cgi?id=72481
Bug ID: 72481
Summary: Compile error for varadic template
Product: gcc
Version: 5.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: liweifriends at gmail dot com
Target Milestone: ---
The code is as follows:
===================================================================
// Code Pos 1
//template <typename...T> struct PolicyContainer;
template <typename...T> struct DummyLayer2;
template <typename TNewPolicy, typename TOriLayer> struct ChangePolicyHelper;
template <typename TNewPolicy, template<typename...> class TLayer, typename...
TPolicies>
struct ChangePolicyHelper<TNewPolicy, TLayer<TPolicies...>>
{
// Code Pos 2
template <typename...T> struct PolicyContainer;
template <typename TPC, typename... TP>
struct DropAppendHelper;
template <typename... TFilteredPolicies>
struct DropAppendHelper<PolicyContainer<TFilteredPolicies...>>
{
using type = DummyLayer2<TFilteredPolicies..., TNewPolicy>;
};
template <typename... TFilteredPolicies, typename TCurPolicy, typename...
TP>
struct DropAppendHelper<PolicyContainer<TFilteredPolicies...>,
TCurPolicy, TP...>
{
using t1 = PolicyContainer<TFilteredPolicies...>;
using type = typename DropAppendHelper<t1, TP...>::type;
};
template <typename...TFilteredPolicies, typename...TCurPolicy,
template<typename...> class TC, typename...TP>
struct DropAppendHelper<PolicyContainer<TFilteredPolicies...>,
TC<TCurPolicy...>, TP...>
{
using t1 = TC<TCurPolicy...>;
using t2 = PolicyContainer<TFilteredPolicies..., t1>;
using type = typename DropAppendHelper<t2, TP...>::type;
};
using type = typename DropAppendHelper<PolicyContainer<>,
TPolicies...>::type;
};
template <typename TLayer>
using SetFeedbackOut = typename ChangePolicyHelper<int, TLayer>::type;
using OriLayer2 = DummyLayer2<DummyLayer2<struct Tag1>>;
using NewLayer2 = SetFeedbackOut<OriLayer2>;
===================================================================
When Compile, the compiler reports an compile error.
However, with the following modification, the code could be compiled:
===================================================================
// Code Pos 1
template <typename...T> struct PolicyContainer;
...
// Code Pos 2
// template <typename...T> struct PolicyContainer;
===================================================================
