How to Resolve Function Name Collision in C Derived Class Inheritance?

Function Name Collision in Derived Class Inheritance

Consider the following code snippet:

class A { public: void foo(string s) {} };
class B : public A { public: int foo(int i) {} };
class C : public B { public: void bar() { string s; foo(s); } };

When compiling this code, the compiler generates the following error:

error: no matching function for call to 'C::foo(std::string&)'
candidates are: int B::foo(int)

This error occurs because of function name shadowing. When the derived class B defines a function with the same name as a function in its base class A, the derived class function shadows the base class function.

Name Lookup Scope

Name lookup in a class scope follows these steps:

1. Consider all declarations for the name in the class and its base classes.
2. Eliminate any declarations hidden by other declarations in base classes.

Solution

To resolve the function name collision, you can re-declare the base class function in the scope of the derived class. This ensures that both functions are visible within the derived class and its descendants:

class A { public: void foo(string s) {} };
class B : public A { public: int foo(int i) {}; using A::foo; };
class C : public B { public: void bar() { string s; foo(s); } };

By adding using A::foo;, you specify that the foo function from the base class A is also available in the derived class B. Now, the code will compile without errors.

Additional Notes

• The Standard defines name lookup in class scope as follows:

"The following steps define the result of name lookup in a class scope, C. First, every declaration for the name in the class and in each of its base class sub-objects is considered. A member name f in one sub-object B hides a member name f in a sub-object A if A is a base class sub-object of B."

• Name lookup occurs before access control. Therefore, even if the foo function in B is private, the foo function in A will still not be found.

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