https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78022
Bug ID: 78022
Summary: Strange C++ compilation error
Product: gcc
Version: 5.4.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: fiesh at zefix dot tv
Target Milestone: ---
The following piece of code does not compile. Since clang 3.8.1 compiles it,
and furthermore changes that would appear inconsequential make it compile, I
suspect it might be an issue of GCC:
------------------
#include <array>
template<typename T>
struct A
{
template<typename... Args>
constexpr A(Args&&... args) :
entries_{std::forward<Args>(args)...} {}
std::array<T, 1> entries_;
};
struct B : public A<int>
{
using A<int>::A;
};
// Uncommenting the following line makes this file compile.
//constexpr B p{0};
// Commenting the following line makes this file compile.
template<typename>
struct X
{
X()
{
// The following line is fine.
const B b0{0};
// The following line produces an error.
constexpr B b1{0};
}
};
------------------
The output is as follows:
% g++ -std=c++11 -c test.cpp
test.cpp: In constructor ‘X<T>::X()’:
test.cpp:31:20: error: ‘constexpr B::B(Args&& ...) [with Args = {int}]’ used
before its definition
constexpr B b1{0};
