CODEWITHSUNDEEP
c++clanglanguage-lawyerc++14inheriting-constructors
Lingxi
Lingxi

Reputation: 14987

Inheriting constructors (GCC and clang disagree)

I'm trying to customize std::function and beginning with the following code:

#include <functional>

template <typename>
struct my_function;

template <typename R, typename... Args>
struct my_function<R(Args...)> : std::function<R(Args...)> {
  using base = std::function<R(Args...)>;

  using base::function;
}; 

int main() {
  my_function<int(int)> f = nullptr;
}

I'm expecting that the constructor from std::function that takes an std::nullptr_t object is inherited by my_function. So, the code should compile fine. While GCC 5.2 (C++14) has no problem in compiling the code, clang 3.6 (C++14) produced the following error message which is quite confusing:

n file included from main.cpp:1:
/usr/include/c++/v1/functional:1454:41: error: no type named 'type' in 'std::__1::enable_if<false, void>'; 'enable_if' cannot be used to disable this declaration
                                        __callable<_Fp>::value &&
                                        ^~~~~~~~~~~~~~~~~~~~~~~~~
main.cpp:10:15: note: in instantiation of member function 'std::__1::function<int (int)>::function' requested here
  using base::function;
              ^
main.cpp:14:25: note: while substituting deduced template arguments into function template 'my_function' [with _Fp = nullptr_t]
  my_function<int(int)> f = nullptr;
                        ^
1 error generated.

Is this a clang bug or my code is just incorrect? If (very fortunately) the latter is true, how should I fix the code?

Upvotes: 3

Views: 413

Answers (0)

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