Re: Hidden overloaded operator in multiple inheritance

Ulrich Eckhardt <>
Mon, 15 Oct 2007 09:11:26 +0200
Alex Blekhman wrote:

"Alex Blekhman" wrote:

class A
   int operator+(int) { return 42; }

class B
   double operator+(double) { return 3.14; }

class C : public A, public B

int main()
   C c1;
   int i = 5;
   double d = 10.5;

   c1 + i; // Error!
   c1 + d; // Error!

   return 0;


Second, I think that VC++ actually does have a bug in call
resolving mechanism. The function name from left base class
`A' actually hides the name from right base class `B'
instead of competing with it for inclusion in name lookup
set. The above code compiles with warning that double is
implicitly converted to int. So, obviously `int A::operator+
(int)' kicked in. If I replace double in class' B `operator
+' with `char*', for example, then I get C2679 ("no
appropriate operator found").

Comeau compiler correctly reports ambiguity error in any
case (double or char*).

I'm not so sure if this is correct. I would have said that the compiler
would find overloads (well, only one) in the first baseclass and stops
searching there. It then tries to match the overloads against the arguments
and doesn't find one. The fact that ambiguity is reported seems wrong to


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