c++/10473: conversion operator from private base used

[dv at vollmann dot ch]

>Number:         10473
>Category:       c++
>Synopsis:       g++ wrongly considers conversion operator from private base
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          rejects-legal
>Submitter-Id:   net
>Arrival-Date:   Wed Apr 23 23:56:00 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     Detlef Vollmann
>Release:        3.4 20030423 (experimental)
>Organization:
vollmann engineering gmbh
>Environment:
System: Linux dwarf 2.4.3-XFS #7 Mon Aug 6 18:43:20 CEST 2001 i686 unknown
Architecture: i686

	
host: i686-pc-linux-gnu
build: i686-pc-linux-gnu
target: i686-pc-linux-gnu
configured with: /pdsrc/gcc/cvs/gcc/configure --program-suffix=-test --prefix=/local/gcc-test --enable-shared --enable-threads=posix --enable-version-specific-runtime-libs --enable-languages=c,c++
>Description:
	If a class defines an operator[] and a private base class defines
	a conversion operator to a pointer, the use of the operator[]
	can cause ambiguities.  This would be correct if the derivation
	would be public, but is wrong if the derivation is private.
>How-To-Repeat:
	See attached file:
inherit-conv.cc:
typedef unsigned int size_t;

class Base
{
public:
    typedef int *value_type;

    Base() {}

    operator value_type() const { return 0; }
    void operator=(value_type val) {}
};

class Derived : private Base
{
public:
    Derived() : p(0) {}

    Base::value_type &operator[](size_t index) { return p; }

private:
    Base::value_type p;
};

int main()
{

    Derived ppBuf;
    int *p = ppBuf[4];
    ppBuf[0] = p;

    return 0;
}
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted: