CODEWITHSUNDEEP
androidc++g++constantsporting
18446744073709551615
18446744073709551615

Reputation: 16832

need a warning about overriding a function with const parameter

How do I make GCC inform me about redefining member functions with a different signature?

I am porting a large project to Android. Due to the differences in the M$VC and GCC dialects, I inserted a number of const modifiers for function parameters. (Namely, when you call func(MyClass(something)), M$ is ok with MyClass& while GCC requires const MyClass&.)

The gotcha is that when you change the signature of BaseClass::func(), you get no warning about having a different signature for DerivedClass::func().

Here is a small program showing what's going on:

#include <stdio.h>
    class Value {
       int x;
       public:
       Value(int xx):x(xx){}
  };
    class Base {
       public:
       virtual void f(const Value&v) {printf("Base\n");}
  };
    class First: public Base {
       public:
       virtual void f(Value&v) {printf("First\n");}
  };
    class Second: public Base {
       public:
       virtual void f(Value&v) {printf("Second\n");}
  };

    int main() {
         Value v(1);
         First first;
         Second second;
         Base*any;
         any = &first;
         any->f(v);
         any->f(Value(2));
         first.f(v);
    //first.f(Value(3)); // error: no matching function for call to 
         First::f(Value)
}

When I compile and run it, I get:

$ g++ -Wall -Wextra inher2.cpp 
    inher2.cpp:10:18: warning: unused parameter ‘v’
    inher2.cpp:15:18: warning: unused parameter ‘v’
    inher2.cpp:20:18: warning: unused parameter ‘v’
$ ./a.out 
    Base
    Base
    First
$

(gcc is right about the unused parameter, but it's irrelevant.)

So: How do I make GCC inform me about redefining member functions with a different signature?

Upvotes: 2

Views: 179

Answers (1)

visitor
visitor

Reputation: 1801

That should be -Woverloaded-virtual.

-Woverloaded-virtual

 Warn when a derived class function declaration may be an error in
 defining a virtual function (C++ only).  In a derived class, the
 definitions of virtual functions must match the type signature of a
 virtual function declared in the base class.  With this option, the
 compiler warns when you define a function with the same name as a
 virtual function, but with a type signature that does not match any
 declarations from the base class.

Upvotes: 4

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