Re: c++/8500: Allows cast to private base class

Re: c++/8500: Allows cast to private base class

[Gabriel Dos Reis]

The following reply was made to PR c++/8500; it has been noted by GNATS.

From: Gabriel Dos Reis <gdr@integrable-solutions.net>
To: gcc-gnats@gcc.gnu.org
Cc:  
Subject: Re: c++/8500: Allows cast to private base class
Date: 11 Nov 2002 12:36:48 +0100

 Wolfgang Bangerth <bangerth@ticam.utexas.edu> writes:
 
 | The following reply was made to PR c++/8500; it has been noted by GNATS.
 | 
 | From: Wolfgang Bangerth <bangerth@ticam.utexas.edu>
 | To: "Harald H. Soleng" <Harald.Soleng@nr.no>
 | Cc: gcc-gnats@gcc.gnu.org
 | Subject: Re: c++/8500: Allows cast to private base class
 | Date: Fri, 8 Nov 2002 14:03:20 -0600 (CST)
 | 
 |  > You should not get an error with old style c-casting.
 |  > However, with 
 |  > 
 |  >         Base* b1 = static_cast<Base*> d1;
 |  > 
 |  > on the second line of main you should. Here is the error message from
 |  > the native Sun CC compiler:
 |  > "Error: Using static_cast to convert from Derived* to Base* not allowed."
 |  
 |  Uhm, I don't think you can work around access control rules just by using 
 |  a C-style cast over a static_cast, can you?
 
 old-style casts don't chech acess control.  New-style casts do, however.
 
 -- Gaby
 
 

Re: c++/8500: Allows cast to private base class

[Wolfgang Bangerth]

The following reply was made to PR c++/8500; it has been noted by GNATS.

From: Wolfgang Bangerth <bangerth@ticam.utexas.edu>
To: "Harald H. Soleng" <Harald.Soleng@nr.no>
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: c++/8500: Allows cast to private base class
Date: Fri, 8 Nov 2002 14:03:20 -0600 (CST)

 > You should not get an error with old style c-casting.
 > However, with 
 > 
 >         Base* b1 = static_cast<Base*> d1;
 > 
 > on the second line of main you should. Here is the error message from
 > the native Sun CC compiler:
 > "Error: Using static_cast to convert from Derived* to Base* not allowed."
 
 Uhm, I don't think you can work around access control rules just by using 
 a C-style cast over a static_cast, can you?
 
 Regards
   W.
 
 -------------------------------------------------------------------------
 Wolfgang Bangerth              email:           bangerth@ticam.utexas.edu
                                www: http://www.ticam.utexas.edu/~bangerth
 
 

Re: c++/8500: Allows cast to private base class

[bangerth]

Synopsis: Allows cast to private base class

State-Changed-From-To: analyzed->closed
State-Changed-By: bangerth
State-Changed-When: Fri Nov  8 07:02:18 2002
State-Changed-Why:
    I think this is actually a duplicate of c++/2330.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8500

Re: c++/8500: Allows cast to private base class

[bangerth]

Synopsis: Allows cast to private base class

State-Changed-From-To: open->analyzed
State-Changed-By: bangerth
State-Changed-When: Fri Nov  8 06:58:52 2002
State-Changed-Why:
    Confirmed. Reduced code looks like this:
    ------------------------------
    class Base {};
    
    class Derived : private Base {
       public:
          Derived () : Base() {}
    };
    
    int main(void) {
       Derived* d1 = new Derived;
       Base* b1 = (Base*) d1;
    }
    ----------------------------------
    Note that we get indeed an error if the cast (Base*) is
    removed, but not with it.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8500