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Date: Wed, 09 Oct 2002 12:46:00 -0000
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From: Andreas Schwab <schwab@suse.de>
Subject: Re: c++/8176: C++ const**, doesn't implictly cast
Reply-To: Andreas Schwab <schwab@suse.de>
X-SW-Source: 2002-10/txt/msg00335.txt.bz2
List-Id: <gcc-prs.sourceware.org>

The following reply was made to PR c++/8176; it has been noted by GNATS.

From: Andreas Schwab <schwab@suse.de>
To: charles@kde.org
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: c++/8176: C++ const**, doesn't implictly cast
Date: Wed, 09 Oct 2002 21:42:03 +0200

 charles@kde.org writes:
 
 |> class Bleh { };
 |> 
 |> void foo(const Bleh **) { }
 |> int main(int, char **)
 |> {
 |> 	Bleh *bleh;
 |> 	foo(&bleh); // broken
 |> 
 |> 	Bleh **bar;
 |> 	foo(bar); // broken
 |> 
 |> 	foo(const_cast<const Bleh**>(bar)); // works
 |> 
 |> 	const Bleh **works;
 |> 	foo(works); // works
 |> }
 |> 
 |> This should work, as <Bleh**> can be casted to <const Bleh**> implicitly
 
 No, you can't.
 
 class Bleh { int what; };
 const Bleh const_bleh;
 void foo(const Bleh **bleh)
 {
    *bleh = &const_bleh;
 }
 int main()
 {
   Bleh *bleh;
   foo(&bleh);        // assume this is valid
   (*bleh)->what = 1; // modifying const_bleh!
 }
 
 Andreas.
 
 -- 
 Andreas Schwab, SuSE Labs, schwab@suse.de
 SuSE Linux AG, Deutschherrnstr. 15-19, D-90429 Nürnberg
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