call of overloaded 'xxx' is ambiguous

这里定义了一个模版函数，功能同STL里的copy函数：

#include <vector> #include <list> #include <iostream> template <typename Iter1, typename Iter2> Iter2 copy(Iter1 f1, Iter1 e1, Iter2 f2) { for (f1; f1 != e1; ++f1, ++f2) { *f1 = *f2; } return f2; } int main() { int arr[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}; std::vector<int> vec{1, 2, 3, 4, 5, 6, 7, 8, 9, 0}; copy(arr, arr + 10, vec.begin()); return 0; }

编译时报了call of overloaded 'copy(int [10], int*, std::vector<int>::iterator)' is ambiguous错误。

c:\Source\drill.cpp: In function 'int main()': c:\Source\drill.cpp:27:36: error: call of overloaded 'copy(int [10], int*, std::vector<int>::iterator)' is ambiguous copy(arr, arr + 10, vec.begin()); ^ c:\Source\drill.cpp:6:7: note: candidate: Iter2 copy(Iter1, Iter1, Iter2) [with Iter1 = int*; Iter2 = __gnu_cxx::__normal_iterator<int*, std::vector<int> >] Iter2 copy(Iter1 f1, Iter1 e1, Iter2 f2) ^~~~ In file included from C:/mingw-w64/lib/gcc/x86_64-w64-mingw32/6.3.0/include/c++/vector:60:0, from c:\Source\drill.cpp:1: C:/mingw-w64/lib/gcc/x86_64-w64-mingw32/6.3.0/include/c++/bits/stl_algobase.h:446:5: note: candidate: _OI std::copy(_II, _II, _OI) [with _II = int*; _OI = __gnu_cxx::__normal_iterator<int*, std::vector<int> >] copy(_II __first, _II __last, _OI __result)

从报错信息可以看出，编译器匹配到了stl_algobase.h里的copy函数，因为我传的参数std::vector::iterator(vec.begin())是属于namespace std的。

解决的办法一：指定命名空间

#include <vector> #include <list> #include <iostream> namespace LK { template <typename Iter1, typename Iter2> Iter2 copy(Iter1 f1, Iter1 e1, Iter2 f2) { for (f1; f1 != e1; ++f1, ++f2) { *f1 = *f2; } return f2; } } int main() { int arr[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}; std::vector<int> vec{1, 2, 3, 4, 5, 6, 7, 8, 9, 0}; LK::copy(arr, arr + 10, vec.begin()); return 0; }

解决的办法二：函数名用括号包住

#include <vector> #include <list> #include <iostream> template <typename Iter1, typename Iter2> Iter2 copy(Iter1 f1, Iter1 e1, Iter2 f2) { for (f1; f1 != e1; ++f1, ++f2) { *f1 = *f2; } return f2; } int main() { int arr[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}; std::vector<int> vec{1, 2, 3, 4, 5, 6, 7, 8, 9, 0}; (copy)(arr, arr + 10, vec.begin()); return 0; }

参考资料

template programming: ambiguous call to overloaded functionArgument-dependent name lookupArgument-dependent lookup

转载于:https://www.cnblogs.com/lkpp/p/argument-dependent-name-koenig-lookup-on-functions.html