C++ compilation error: reference to constructor is ambiguous [closed] - c++

Question

This question is unlikely to help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet. For help making this question more broadly applicable, visit the help center.
Closed 10 years ago.
I have a single source file C++ program I'm trying to compile.
The header file looks like:
class merge {
public:
explicit merge(int argc, char* argv[]);
virtual ~merge();
};
And the source file looks like:
int main(int argc, char* argv[])
{
merge mrg(argc,argv);
return 0;
}
merge::merge(map<string,string>& params) {
//code
}
Trying to compile with:
g++ merge.cpp -o merge
I get:
merge.cpp: In function ‘int main(int, char**)’:
merge.cpp:10: error: reference to ‘merge’ is ambiguous
merge.h:12: error: candidates are: class merge
/usr/lib/gcc/x86_64-redhat- linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_algo.h:3180: error: template<class _InputIterator1, class _InputIterator2, class _OutputIterator, class _Compare> _OutputIterator std::merge(_InputIterator1, _InputIterator1, _InputIterator2, _InputIterator2, _OutputIterator, _Compare)
/usr/lib/gcc/x86_64-redhat- linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_algo.h:3122: error: template<class _InputIterator1, class _InputIterator2, class _OutputIterator> _OutputIterator std::merge(_InputIterator1, _InputIterator1, _InputIterator2, _InputIterator2, _OutputIterator)
merge.cpp:10: error: reference to ‘merge’ is ambiguous
merge.h:12: error: candidates are: class merge
/usr/lib/gcc/x86_64-redhat- linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_algo.h:3180: error: template<class _InputIterator1, class _InputIterator2, class _OutputIterator, class _Compare> _OutputIterator std::merge(_InputIterator1, _InputIterator1, _InputIterator2, _InputIterator2, _OutputIterator, _Compare)
/usr/lib/gcc/x86_64-redhat- linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_algo.h:3122: error: template<class _InputIterator1, class _InputIterator2, class _OutputIterator> _OutputIterator std::merge(_InputIterator1, _InputIterator1, _InputIterator2, _InputIterator2, _OutputIterator)
merge.cpp:10: error: expected `;' before ‘mrg’
merge.cpp: At global scope:
merge.cpp:14: error: prototype for ‘merge::merge(std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >&)’ does not match any in class ‘merge’
merge.h:12: error: candidates are: merge::merge(const merge&)
merge.h:14: error: merge::merge(int, char**)
merge.cpp: In constructor ‘merge::merge(std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >&)’:
merge.cpp:15: error: declaration of ‘std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<const std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > > params’ shadows a parameter
merge.cpp:16: error: ‘argc’ was not declared in this scope
merge.cpp:16: error: ‘argv’ was not declared in this scope
/usr/lib/gcc/x86_64-redhat- linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_iterator_base_types.h: At global scope:
/usr/lib/gcc/x86_64-redhat- linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_iterator_base_types.h: In instantiation of ‘std::iterator_traits<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >’:
/usr/lib/gcc/x86_64-redhat- linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_vector.h:803: instantiated from ‘void std::vector<_Tp, _Alloc>::_M_initialize_dispatch(_InputIterator, _InputIterator, __false_type) [with _InputIterator = std::basic_string<char, std::char_traits<char>, std::allocator<char> >, _Tp = int, _Alloc = std::allocator<int>]’
/usr/lib/gcc/x86_64-redhat- linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_vector.h:262: instantiated from ‘std::vector<_Tp, _Alloc>::vector(_InputIterator, _InputIterator, const _Alloc&) [with _InputIterator = std::basic_string<char, std::char_traits<char>, std::allocator<char> >, _Tp = int, _Alloc = std::allocator<int>]’
merge.cpp:86: instantiated from here
/usr/lib/gcc/x86_64-redhat- linux/4.1.2/../../../../include/c++/4.1.2/bits/stl_iterator_base_types.h:129: error: no type named ‘iterator_category’ in ‘struct std::basic_string<char, std::char_traits<char>, std::allocator<char> >’
Any idea what's wrong?

Answer 1

In the class declaration you have
explicit merge(int argc, char* argv[]);
But when you provide a definition for the constructor you have
merge::merge(map<string,string>& params) { /* ... */ }
Of course, the two must match.
Also, it seems you have a using namespace std; statement in your code somewhere. The compiler cannot resolve whether the calls to merge are to your merge class constructor or to std::merge.
The lesson to take away from this (other than fix your constructor):
DO NOT add using namespace std; anywhere in your code. std:: is not very cumbersome to type.

Answer 2

The signature of merge's constructor does not match its definition.
In your class declaration, you defined merge::merge to take in two parameters, one int and the other char*. In the definition for merge::merge, however, you define it as taking in only one parameter of type map<string,string>&