I have a class like:
#include <memory> class Object { std::shared_ptr<void> object_ptr; public: Object() {} template<typename T> Object(T&& object) : object_ptr {new T {std::move(object)} } {} virtual ~Object() {}; };
My main cpp file:
#include <iostream> #include "Object.hpp" class Foo {}; int main() { Object o {Foo{}}; }
This gives me an error:
test/test.cpp:13:20: required from here include/Object.hpp:24:49: error: could not convert '{std::move<Foo&>((* & object))}' from '<brace-enclosed initializer list>' to 'Foo' : object_ptr {new T {std::move(object)} } {} ^ include/Object.hpp:24:49: error: no matching function for call to 'std::shared_ptr<void>::shared_ptr(<brace-enclosed initializer list>)' include/Object.hpp:24:49: note: candidates are: In file included from /usr/include/c++/4.8/memory:82:0, from include/Object.hpp:7, from test/test.cpp:2: /usr/include/c++/4.8/bits/shared_ptr.h:314:2: note: template<class _Alloc, class ... _Args> std::shared_ptr<_Tp>::shared_ptr(std::_Sp_make_shared_tag, const _Alloc&, _Args&& ...) shared_ptr(_Sp_make_shared_tag __tag, const _Alloc& __a, ^ /usr/include/c++/4.8/bits/shared_ptr.h:314:2: note: template argument deduction/substitution failed: /usr/include/c++/4.8/bits/shared_ptr.h:265:17: note: constexpr std::shared_ptr<_Tp>::shared_ptr(std::nullptr_t) [with _Tp = void; std::nullptr_t = std::nullptr_t] constexpr shared_ptr(nullptr_t __p) noexcept ^ /usr/include/c++/4.8/bits/shared_ptr.h:265:17: note: no known conversion for argument 1 from '<type error>' to 'std::nullptr_t' /usr/include/c++/4.8/bits/shared_ptr.h:257:2: note: template<class _Tp1, class _Del> std::shared_ptr<_Tp>::shared_ptr(std::unique_ptr<_Up, _Ep>&&) shared_ptr(std::unique_ptr<_Tp1, _Del>&& __r) ^ /usr/include/c++/4.8/bits/shared_ptr.h:257:2: note: template argument deduction/substitution failed: /usr/include/c++/4.8/bits/shared_ptr.h:253:2: note: template<class _Tp1> std::shared_ptr<_Tp>::shared_ptr(std::auto_ptr<_Up>&&) shared_ptr(std::auto_ptr<_Tp1>&& __r); ^ /usr/include/c++/4.8/bits/shared_ptr.h:253:2: note: template argument deduction/substitution failed: /usr/include/c++/4.8/bits/shared_ptr.h:248:11: note: template<class _Tp1> std::shared_ptr<_Tp>::shared_ptr(const std::weak_ptr<_Tp1>&) explicit shared_ptr(const weak_ptr<_Tp1>& __r) ^ /usr/include/c++/4.8/bits/shared_ptr.h:248:11: note: template argument deduction/substitution failed: /usr/include/c++/4.8/bits/shared_ptr.h:236:2: note: template<class _Tp1, class> std::shared_ptr<_Tp>::shared_ptr(std::shared_ptr<_Tp1>&&) shared_ptr(shared_ptr<_Tp1>&& __r) noexcept ^ /usr/include/c++/4.8/bits/shared_ptr.h:236:2: note: template argument deduction/substitution failed: /usr/include/c++/4.8/bits/shared_ptr.h:226:7: note: std::shared_ptr<_Tp>::shared_ptr(std::shared_ptr<_Tp>&&) [with _Tp = void] shared_ptr(shared_ptr&& __r) noexcept ^ /usr/include/c++/4.8/bits/shared_ptr.h:226:7: note: no known conversion for argument 1 from '<type error>' to 'std::shared_ptr<void>&&' /usr/include/c++/4.8/bits/shared_ptr.h:218:2: note: template<class _Tp1, class> std::shared_ptr<_Tp>::shared_ptr(const std::shared_ptr<_Tp1>&) shared_ptr(const shared_ptr<_Tp1>& __r) noexcept ^ /usr/include/c++/4.8/bits/shared_ptr.h:218:2: note: template argument deduction/substitution failed: /usr/include/c++/4.8/bits/shared_ptr.h:206:2: note: template<class _Tp1> std::shared_ptr<_Tp>::shared_ptr(const std::shared_ptr<_Tp1>&, _Tp*) shared_ptr(const shared_ptr<_Tp1>& __r, _Tp* __p) noexcept ^ /usr/include/c++/4.8/bits/shared_ptr.h:206:2: note: template argument deduction/substitution failed: /usr/include/c++/4.8/bits/shared_ptr.h:184:2: note: template<class _Deleter, class _Alloc> std::shared_ptr<_Tp>::shared_ptr(std::nullptr_t, _Deleter, _Alloc) shared_ptr(nullptr_t __p, _Deleter __d, _Alloc __a) ^ /usr/include/c++/4.8/bits/shared_ptr.h:184:2: note: template argument deduction/substitution failed: /usr/include/c++/4.8/bits/shared_ptr.h:165:2: note: template<class _Tp1, class _Deleter, class _Alloc> std::shared_ptr<_Tp>::shared_ptr(_Tp1*, _Deleter, _Alloc) shared_ptr(_Tp1* __p, _Deleter __d, _Alloc __a) ^ /usr/include/c++/4.8/bits/shared_ptr.h:165:2: note: template argument deduction/substitution failed: /usr/include/c++/4.8/bits/shared_ptr.h:146:2: note: template<class _Deleter> std::shared_ptr<_Tp>::shared_ptr(std::nullptr_t, _Deleter) shared_ptr(nullptr_t __p, _Deleter __d) ^ /usr/include/c++/4.8/bits/shared_ptr.h:146:2: note: template argument deduction/substitution failed: /usr/include/c++/4.8/bits/shared_ptr.h:129:2: note: template<class _Tp1, class _Deleter> std::shared_ptr<_Tp>::shared_ptr(_Tp1*, _Deleter) shared_ptr(_Tp1* __p, _Deleter __d) ^ /usr/include/c++/4.8/bits/shared_ptr.h:129:2: note: template argument deduction/substitution failed: /usr/include/c++/4.8/bits/shared_ptr.h:112:11: note: template<class _Tp1> std::shared_ptr<_Tp>::shared_ptr(_Tp1*) explicit shared_ptr(_Tp1* __p) ^ /usr/include/c++/4.8/bits/shared_ptr.h:112:11: note: template argument deduction/substitution failed: /usr/include/c++/4.8/bits/shared_ptr.h:103:7: note: std::shared_ptr<_Tp>::shared_ptr(const std::shared_ptr<_Tp>&) [with _Tp = void] shared_ptr(const shared_ptr&) noexcept = default; ^ /usr/include/c++/4.8/bits/shared_ptr.h:103:7: note: no known conversion for argument 1 from '<type error>' to 'const std::shared_ptr<void>&' /usr/include/c++/4.8/bits/shared_ptr.h:100:17: note: constexpr std::shared_ptr<_Tp>::shared_ptr() [with _Tp = void] constexpr shared_ptr() noexcept ^ /usr/include/c++/4.8/bits/shared_ptr.h:100:17: note: candidate expects 0 arguments, 1 provided make: *** [test.o] Error 1
However, if I change new T {std::move(object)} to new T (std::move(object)) . He works:
class Object { std::shared_ptr<void> object_ptr; public: Object() {} template<typename T> Object(T&& object) : object_ptr {new T (std::move(object)) } {} virtual ~Object() {}; };
Why does brace with uniform initialization not work here? Why in this case is considered an initializer list? Foo doesn't even have a constructor that accepts a list of initializers?