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Re: c++/3242: Forwarding using 'using' of base members broken? (see also c++/3283)
- To: nobody at gcc dot gnu dot org
- Subject: Re: c++/3242: Forwarding using 'using' of base members broken? (see also c++/3283)
- From: Wolfgang Wander <wwc at rentec dot com>
- Date: 20 Jun 2001 14:16:05 -0000
- Cc: gcc-prs at gcc dot gnu dot org,
- Reply-To: Wolfgang Wander <wwc at rentec dot com>
The following reply was made to PR c++/3242; it has been noted by GNATS.
From: Wolfgang Wander <wwc@rentec.com>
To: gcc-gnats@gcc.gnu.org
Cc: maeder@glue.ch
Subject: Re: c++/3242: Forwarding using 'using' of base members broken? (see also c++/3283)
Date: Wed, 20 Jun 2001 10:13:49 -0400 (EDT)
>Submitter-Id: net
>Originator: Wolfgang Wander
>Organization:
>Confidential: no
>Synopsis: Forwarding using 'using' of base members broken?
>Severity: serious
>Priority: medium
>Category: c++
>Class: rejects-legal
>Release: 3.0
>Environment:
System: Linux localhost 2.4.3-ac12 #18 Sun Apr 22 23:29:30 EDT 2001 i686 unknown
System: SunOS localhost 5.7 Generic_106541-12 sun4u sparc SUNW,Ultra-4
System: any?
Architecture: sun4
host: sparc-sun-solaris2.7
build: sparc-sun-solaris2.7
target: sparc-sun-solaris2.7
configured with: /work/external/src/gcc-3.0/configure --prefix=/work/external/ --enable-long-long --enable-languages=c++
>Description:
Since the first bug report did not include the full cpp output
and Thomas' one did neither - here is a one that is standalone and does
not use the new libstdc++.
A using declaration does not forward all of the overloaded
member functions.
KaiCC/SunCC and g++-2.95 (as well as the standard AFAIK)
agree that the code below is legal code.
>How-To-Repeat:
---
template <typename T>
struct Base {
typedef T &type;
typedef const T &const_type;
type foo();
const_type foo() const;
};
struct Derived: private Base<int> {
using Base<int>::type;
using Base<int>::const_type;
using Base<int>::foo;
};
void foo() {
Derived d;
Derived::type b = d.foo();
Derived::const_type c = d.foo();
}
---
$ g++-3.0 test.C
test.C: In function `void foo()':
test.C:18: conversion from `const int' to `int&' discards qualifiers
This bug affects all forwarding of overloaded STL container members
like begin/end/find/...
>Fix:
A workaround:
forward the members manually in the derived class:
struct Derived: private Base<int> {
using Base<int>::type;
using Base<int>::const_type;
type foo() { return Base<int>::foo(); }
const_type foo() const { return Base<int>::foo(); }
};