C++ overloaded function issue

Question

Why does the compiler not find the base class function signature? Changing foo( a1 ) to B::foo( a1 ) works.

Code:

class A1 ;
class A2 ;

class B
{
public:
   void foo( A1* a1 ) { a1 = 0 ; }
} ;

class C : public B
{
public:
   void foo( A2* /*a2*/ )
   {
      A1* a1 = 0 ;
      foo( a1 ) ;
   }
} ;

int main()
{
   A2* a2 = 0 ;
   C c ;
   c.foo( a2 ) ;
   return 0 ;
}

Compiler error (VS2008):

error C2664: 'C::foo' : cannot convert parameter 1 from 'A1 *' to 'A2 *'
Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast

Do you get that error on the last line of `C::foo` or `main`? — Adam Maras, Nov 25 '09 at 19:49
It is called "name hiding". Read the FAQ: http://www.parashift.com/c++-faq-lite/strange-inheritance.html#faq-23.9 — AnT stands with Russia, Nov 25 '09 at 19:56
Possible duplicates: http://stackoverflow.com/questions/411103/ http://stackoverflow.com/questions/1480085/ — CB Bailey, Nov 25 '09 at 19:57

score 5 · Accepted Answer · edited Jul 06 '18 at 20:07

5

The name C::foo shadows the name B::foo. Once the compiler finds the matching foo in class C, it stops searching any further.

You can resolve your problem by adding:

using B::foo;

to the body of class C, or by renaming the function in class B.

edited Jul 06 '18 at 20:07

answered Nov 25 '09 at 19:48

James McNellis

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Also, main is not allowed to be void. It must return an int, by C++ standard. – ChrisInEdmonton Nov 25 '09 at 19:52
You can also make the function virtual in class B. – ChrisInEdmonton Nov 25 '09 at 19:53
My question now adheres to the C++ standard. – swongu Nov 25 '09 at 19:54
@ChrisInEdmonton: Making the functions virtual won't resolve this problem because the two declarations of `foo` have different signatures. – James McNellis Nov 25 '09 at 22:11

C++ overloaded function issue

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