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Date: Tue, 11 Jun 2002 14:46:00 -0000
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From: Gabriel Dos Reis <gdr@codesourcery.com>
Subject: Re: c++/7000: Compiler not picking up inherited function from base-class
Reply-To: Gabriel Dos Reis <gdr@codesourcery.com>
X-SW-Source: 2002-06/txt/msg00255.txt.bz2
List-Id: <gcc-prs.sourceware.org>

The following reply was made to PR c++/7000; it has been noted by GNATS.

From: Gabriel Dos Reis <gdr@codesourcery.com>
To: f_ker@yahoo.co.uk
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: c++/7000: Compiler not picking up inherited function from base-class
Date: 11 Jun 2002 23:39:37 +0200

 f_ker@yahoo.co.uk writes:
 
 [...]
 
 | I am trying to use a generic base class to supply an operator()(T*) for all classes that have an operator()(T&) - but the compiler doesn't seem to pick up the operator()(T*) from the base class, and complains and rejects the code that   tried to call it.
 
 This is not a compiler misbehaviour, not a standard-conformant one.
 The declarations of operator()(T&) are overriding the corresponding
 pure virtual function in the base case _and_ *hiding* any other
 overloads.  The moral is that you don't want to overload a pure
 virtual function.
 
 | Code:
 | 
 | #include <vector>
 | #include <algorithm>
 | 
 | template<typename RefToPtrFObjConvertor_T_>
 | class RefToPtrFObjConvertor
 | {
 | public:
 |   virtual void
 |   operator()(RefToPtrFObjConvertor_T_& arg) = 0;
 | 
 |   virtual void
 |   operator()(RefToPtrFObjConvertor_T_* arg)
 |   {
 |     operator()(*arg);
 |   }
 | 
 | };
 | 
 | struct Vertex
 | {
 |   bool is_transformed;
 | 
 |   class SetIsTransformedFlag
 |     : public RefToPtrFObjConvertor<Vertex>
 |   {
 |   public:
 |     bool value;
 | 
 |     SetIsTransformedFlag(bool arg)
 |      : value(arg)
 |     {
 |     }
 | 
 |     void
 |     operator()(Vertex& v)
 
 This declaration hides RefToPtrFObjConvertor<Vertex>::operator()(Vertex*).
 Hence the error message (perhaps cryptic).  
 
 -- Gaby