C / C++ / MFC

hawkgao0129 wrote:

the following code is really compilable in VC++6.0

class TestString {
   CString m_str;
public:
   TestString(TCHAR* str):m_str(str) {}
   operator CString() const {return m_str;}
   <big>friend CString operator+(const TestString& t1, const TestString& t2) { return (CString)t1 + t2; }</big>
};

hawkgao0129 wrote:

The real reason for that problem is, "Argument-Dependent Name Lookup" and "Conversion Functions" cannot work together

hawkgao0129 wrote:

ADL finds operator+ in CStringT

1>c:\build\test\test\test.cpp(19) : error C3767: '+': candidate function(s) not accessible
1>        could be the friend function at 'c:\program files\microsoft visual studio 9.0\vc\atlmfc\include\atlsimpstr.h(653)' : '+'  [may be found via argument-dependent lookup]
...

namespace Test
{
   class A
   {
   public:
      friend void TestFn(const A&) { }
   };
   class B
   {
   public:
      operator A(){ return A(); }
   };
}


class C
{
public:
   operator Test::A(){ return Test::A(); }
};

using namespace Test;

void X()
{
   A a;
   B b;
   C c;
   
   TestFn(a);    // Should be OK
   TestFn((A)b); // Should be OK, as explicitly calling out A as parameter type
   TestFn((A)c); // Should be OK, as explicitly calling out A as parameter type
   TestFn(b);    // Should fail to compile - although in same namespace, friends at class scope are invisible outside the class.
   TestFn(c);    // Should fail to compile - different namespace, ADL won't be used.
}

error C3767: 'TestFn': candidate function(s) not accessible
        could be the friend function at 'd.cpp(6)' : 'TestFn'  [may be found via argument-dependent lookup]

template<class ListType>
void DeleteTheList(ListType& list)
{
   // Do what you need to delete the list
}