Clang，std :: shared_ptr和std :: less / operator<

本文介绍了Clang，std :: shared_ptr和std :: less / operator&lt;的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 拥有以下代码 #include< memory> int main（）{ std :: shared_ptr< int> ptr0（new int）; std :: shared_ptr< int> ptr1（new int）; bool result = ptr0< ptr1;使用clang（版本3.1，LLVM 3.1，LLVM 3.1）编译时，会产生以下错误：} $ b / usr / bin /../ lib / gcc / x86_64-linux-gnu / ../../../../include/c++/4.7/bits/shared_ptr.h:364:14：error：没有匹配的函数调用类型'std :: less< _CT>'$ b的对象$ b return std :: less< _CT>（）（__ a.get（），__b.get（））; ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ int>'request here bool result = ptr0< ptr1; ^ /usr/bin/../lib/gcc/x86_64-linux-gnu/4.7/../../../../include/c++/4.7/bits/stl_function .h：236：7：注意：候选函数不可行：对于，没有从'int *'到'int *&&&'的已知转换。 operator（）（const _Tp& __x，const _Tp& __y）const ^ 使用GCC（版本4.7.0）编译相同的代码不会抛出任何错误消息。有没有理由为什么操作符<（）不适用于clang中的共享指针？解决方案 clang ++和libstdc ++匹配完美。您可以执行以下操作之一： 切换到libc ++（使用 clang ++ -stdlib = libc ++ -std = c ++ 11 ... ） 将以下补丁应用于 / usr / include / c ++ / 4.7.0 / type_traits （如 http://clang.llvm.org/cxx_status中所述。 html ）： 索引：include / std / type_traits = ==================================================== ============== --- include / std / type_traits（revision 185724） +++ include / std / type_traits（working copy） @@ -1746,7 +1746,7 @@ 模板< typename _Tp，typename _Up> struct common_type< _Tp，_Up> - {typedef decltype（true？declval< _Tp>（）：declval< _Up>（））type; }; + {typedef typename decay< decltype（true？declat< _Tp>（）：declval< _Up>（））> :: type type; }; template< typename _Tp，typename _Up，typename ... _V​​p> struct common_type< _Tp，_Up，_Vp ...> 你找到了一个 std :: common_type ，clang开发者声称它实际上是libstdc ++的错误，虽然我不相信libstdc ++的错误会导致不存在的类型 int *&&&& 。 Having the following code#include <memory>int main() { std::shared_ptr<int> ptr0( new int ); std::shared_ptr<int> ptr1( new int ); bool result = ptr0 < ptr1;}produces the following error when being compiled with clang (version 3.1, LLVM 3.1, Debian GNU/Linux Sid)/usr/bin/../lib/gcc/x86_64-linux-gnu/4.7/../../../../include/c++/4.7/bits/shared_ptr.h:364:14: error: no matching function for call to object of type 'std::less<_CT>' return std::less<_CT>()(__a.get(), __b.get()); ^~~~~~~~~~~~~~~~foo.cpp:9:21: note: in instantiation of function template specialization 'std::operator<<int, int>' requested here bool result = ptr0 < ptr1; ^/usr/bin/../lib/gcc/x86_64-linux-gnu/4.7/../../../../include/c++/4.7/bits/stl_function.h:236:7: note: candidate function not viable: no known conversion from 'int *' to 'int *&&&' for 1st argument; operator()(const _Tp& __x, const _Tp& __y) const ^Compiling the same code with GCC (version 4.7.0) doesn't throw any error messages. Is there a reason why operator<() doesn't work for shared pointers in clang? 解决方案 clang++ and libstdc++ doesn't match perfectly yet. You could do one of the followings:Switch to libc++ (by using clang++ -stdlib=libc++ -std=c++11 ...)Apply the following patch to /usr/include/c++/4.7.0/type_traits (as documented in http://clang.llvm.org/cxx_status.html):Index: include/std/type_traits===================================================================--- include/std/type_traits (revision 185724)+++ include/std/type_traits (working copy)@@ -1746,7 +1746,7 @@ template<typename _Tp, typename _Up> struct common_type<_Tp, _Up>- { typedef decltype(true ? declval<_Tp>() : declval<_Up>()) type; };+ { typedef typename decay<decltype(true ? declval<_Tp>() : declval<_Up>())>::type type; }; template<typename _Tp, typename _Up, typename... _Vp> struct common_type<_Tp, _Up, _Vp...>If you check bits/shared_ptr.h you did find a std::common_type, and the clang developers claim that it's actually a bug of libstdc++, although I don't believe a bug of libstdc++ alone would cause the non-existent type int*&&& to appear. 这篇关于Clang，std :: shared_ptr和std :: less / operator&lt;的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！