【发布时间】：2014-01-22 13:00:52
【问题描述】：
以下代码在clang（llvm 5.0版）下似乎无法编译：
#include <functional>
int main()
{
int i;
std::function<void(int&)> f;
std::function<void()> f2 = std::bind(f, std::ref(i));
}
如果f 声明如下（即，不是std::function），那么它编译得很好：
void f(int& n1);
是我做错了什么还是真的是编译器错误？
这是我得到的编译器错误：
In file included from test.cpp:1:
In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/functional:465:
In file included from /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/memory:599:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/tuple:234:73: error: no matching constructor for initialization of 'std::__1::reference_wrapper<int>'
_NOEXCEPT_(is_nothrow_default_constructible<_Hp>::value) : value()
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/tuple:447:23: note: in instantiation of member function 'std::__1::__tuple_leaf<0, std::__1::reference_wrapper<int>, false>::__tuple_leaf' requested here
_LIBCPP_CONSTEXPR __tuple_impl()
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/tuple:550:23: note: in instantiation of member function 'std::__1::__tuple_impl<std::__1::__tuple_indices<0>, std::__1::reference_wrapper<int> >::__tuple_impl' requested
here
_LIBCPP_CONSTEXPR tuple()
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/functional:1744:11: note: in instantiation of member function 'std::__1::tuple<std::__1::reference_wrapper<int> >::tuple' requested here
__bound_args_(_VSTD::forward<_BA>(__bound_args)...) {}
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/memory:2243:15: note: in instantiation of function template specialization 'std::__1::__bind<std::__1::function<void (int &)> &, std::__1::reference_wrapper<int>
>::__bind<std::__1::__bind<std::__1::function<void (int &)> &, std::__1::reference_wrapper<int> >, , void>' requested here
__first_(_VSTD::forward<_Args1>(get<_I1>(__first_args))...)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/memory:2421:15: note: in instantiation of function template specialization 'std::__1::__libcpp_compressed_pair_imp<std::__1::__bind<std::__1::function<void (int &)> &,
std::__1::reference_wrapper<int> >, std::__1::allocator<std::__1::__bind<std::__1::function<void (int &)> &, std::__1::reference_wrapper<int> > >, 2>::__libcpp_compressed_pair_imp<std::__1::__bind<std::__1::function<void (int &)> &,
std::__1::reference_wrapper<int> > &&, , 0, >' requested here
: base(__pc, _VSTD::move(__first_args), _VSTD::move(__second_args),
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/functional:992:11: note: in instantiation of function template specialization 'std::__1::__compressed_pair<std::__1::__bind<std::__1::function<void (int &)> &,
std::__1::reference_wrapper<int> >, std::__1::allocator<std::__1::__bind<std::__1::function<void (int &)> &, std::__1::reference_wrapper<int> > > >::__compressed_pair<std::__1::__bind<std::__1::function<void (int &)> &, std::__1::reference_wrapper<int> > &&, >'
requested here
: __f_(piecewise_construct, _VSTD::forward_as_tuple(_VSTD::move(__f)),
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/functional:1277:26: note: in instantiation of member function 'std::__1::__function::__func<std::__1::__bind<std::__1::function<void (int &)> &,
std::__1::reference_wrapper<int> >, std::__1::allocator<std::__1::__bind<std::__1::function<void (int &)> &, std::__1::reference_wrapper<int> > >, void ()>::__func' requested here
::new (__f_) _FF(_VSTD::move(__f));
^
test.cpp:7:29: note: in instantiation of function template specialization 'std::__1::function<void ()>::function<std::__1::__bind<std::__1::function<void (int &)> &, std::__1::reference_wrapper<int> > >' requested here
std::function<void()> f2 = std::bind(f, std::ref(i));
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__functional_base:365:31: note: candidate constructor not viable: requires single argument '__f', but no arguments were provided
_LIBCPP_INLINE_VISIBILITY reference_wrapper(type& __f) _NOEXCEPT : __f_(&__f) {}
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__functional_base:367:14: note: candidate constructor not viable: requires 1 argument, but 0 were provided
private: reference_wrapper(type&&); public: // = delete; // do not bind to temps
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__functional_base:354:24: note: candidate constructor (the implicit copy constructor) not viable: requires 1 argument, but 0 were provided
class _LIBCPP_TYPE_VIS reference_wrapper
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/c++/v1/__functional_base:354:24: note: candidate constructor (the implicit move constructor) not viable: requires 1 argument, but 0 were provided
1 error generated.
【问题讨论】：
-
除了你提到的问题之外，似乎还有很多其他问题；也许你应该先解决它们。
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对我来说看起来像一个错误。 GCC 4.8.1 和 Clang (3.5trunk) 都编译得很好。
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@scott 还有什么问题？我已经用完整的示例代码和这个简单程序的错误输出更新了帖子，以明确没有其他代码给出问题。
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@DanielFrey Coliru 使用 libstdc++ 还是 libc++？如果 libstdc++ 和 libc++ 之间存在差异，那也可以解释它，并且仍然会在较新的 clang 版本中失败。
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@hvd 默认情况下，他们似乎使用 libstdc++，如果你提供 -stdlib=libc++，linker fails。嗯，有人知道怎么解决吗？
标签： c++ c++11 compiler-errors clang