redefinition of 'WhatEver' as different kind of symbol [duplicate]

Question

This question already has answers here:

Why is "using namespace std;" considered bad practice? (41 answers)

Closed 8 years ago.

I'm trying to migrate some legacy code into a newer project and I don't really get this one fixed. The code compiled and worked well in the older environment.

I have a header file which contains these definitions:

std::string ToString(shared_ptr<const SomeObject> obj);
std::string ToString(SomeObject* obj);

And an implementation file with following lines:

using namespace std;

string ToString(shared_ptr<const SomeObject> obj)
{
  // code cut
  return outstring.str();
}

string ToString(SomeObject* obj)
{
  // code cut
  return outstring.str();
}

I'm trying to compile it with clang and I get the following redefinition error:

.../Filename.cxx:15:8: error: redefinition of 'ToString' as different
      kind of symbol
string ToString(shared_ptr<const SomeObject> obj)
       ^
.../Filename.h:15:13: note: previous definition is here
std::string ToString(SomeObject* obj);

Why is it a redefinition as different kind of symbol? How should I fix this? And last but not least, why does it work with older compilers?

Answer 1

Check if string and shared_ptr are declared, and try specifying namespaces for them (replace shared_ptr with boost::shared_ptr or std::shared_ptr) to make sure that the same class is used in declaration and implementation of ToString.