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Re: removing constness of a true const

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Victor Bazarov wrote:
> On 7/14/2011 5:33 PM, Bo Persson wrote:
>> siddhu wrote:
>>> On Jul 14, 1:05 pm, "Balog Pal"<p...@lib.hu>  wrote:
>>>> "siddhu"<siddharth....@gmail.com>
>>>>
>>>>> I guess removing constness of a true const( I guess it is also
>>>>> called bitwise const ) using const_cast is undefined behavior.
>>>>> Can you please give an example of a true const and may be a
>>>>> sample code which exhibits undefined behavior by removing
>>>>> constness of a true const.
>>>>
>>>> Removing constness is well defined. But actually modifying
>>>> non-mutable member of a const object is UB. By any means,
>>>> including the use of pointer/ref from const_cast.
>>>
>>> Thanks Balog!
>>> Does that mean removing constness of 'this' in const member
>>> function is an UB?
>>
>> It is if the object is really const.
>>
>> Suppose the data is stored in a ROM. What happens when you try to
>> change it?
>
> I see two concepts here, removing of 'const' and changing.  I don't
> think that the former is the same as the latter, or is it?
>
> V

Right, casting away const as such is ok, as long as you don't use it 
for anything non-const.

My point was more that class objects can very well be read-only. 
Trying to change them will then have an undefined result.



Bo Persson

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Thread

removing constness of a true const siddhu <siddharth.sng@gmail.com> - 2011-07-14 08:07 -0700
  Re: removing constness of a true const Victor Bazarov <v.bazarov@comcast.invalid> - 2011-07-14 11:55 -0400
    Re: removing constness of a true const siddhu <siddharth.sng@gmail.com> - 2011-07-14 09:25 -0700
      Re: removing constness of a true const Victor Bazarov <v.bazarov@comcast.invalid> - 2011-07-14 16:18 -0400
        Re: removing constness of a true const "Balog Pal" <pasa@lib.hu> - 2011-07-15 01:18 +0200
          Re: removing constness of a true const Victor Bazarov <v.bazarov@comcast.invalid> - 2011-07-15 08:17 -0400
            Re: removing constness of a true const "Balog Pal" <pasa@lib.hu> - 2011-07-15 18:04 +0200
              Re: removing constness of a true const Ian Collins <ian-news@hotmail.com> - 2011-07-16 08:36 +1200
                Re: removing constness of a true const "Balog Pal" <pasa@lib.hu> - 2011-07-16 02:00 +0200
            Re: removing constness of a true const Paavo Helde <myfirstname@osa.pri.ee> - 2011-07-15 16:08 -0500
              Re: removing constness of a true const Ian Collins <ian-news@hotmail.com> - 2011-07-16 09:30 +1200
  Re: removing constness of a true const "Balog Pal" <pasa@lib.hu> - 2011-07-14 19:05 +0200
    Re: removing constness of a true const siddhu <siddharth.sng@gmail.com> - 2011-07-14 12:05 -0700
      Re: removing constness of a true const "Bo Persson" <bop@gmb.dk> - 2011-07-14 23:33 +0200
        Re: removing constness of a true const Victor Bazarov <v.bazarov@comcast.invalid> - 2011-07-14 17:46 -0400
          Re: removing constness of a true const "Bo Persson" <bop@gmb.dk> - 2011-07-16 08:32 +0200
  Re: removing constness of a true const "Johannes Schaub (litb)" <schaub.johannes@googlemail.com> - 2011-07-15 15:02 +0200
    Re: removing constness of a true const Victor Bazarov <v.bazarov@comcast.invalid> - 2011-07-15 09:54 -0400

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