Hello Steven,
On Mon, 09 Aug 2010 09:57:47 -0400, bearophile
<bearophileh...@lycos.com> wrote:
Steven Schveighoffer:
I thought it was "you're on your own", not undefined behavior. The
former
implies there is some "right" way to do this if you know more about
the
data than the compiler, the latter implies that there is no right
way to
cast away const. Am I wrong?
In my opinion if this thing is well designed then you go in undefined
behaviour only when you change the contents of something after you
have removed its const nature with a cast. Just casting const away
and then reading the data can't be undefined behaviour, otherwise
casting const away is useless and can be totally disallowed.
Casting away const just to read the data is useless. You can read
const data without a cast.
But my understanding is that casting away const to write should be
doable if you know what you're doing. If this is undefined behavior,
then that's fine, I'm just unclear on what "undefined behavior"
actually means. I thought "undefined behavior" means that you cannot
count on the behavior to work in the future.
Undefined behavior implies exactly that, once you enter the realm of undefined
behavior, /anything/ that happens is your fault, the program can do anything
at all and sill be considered a conforming program. It need not even behave
the same between one run and the next.
The practical implications of this are that compilers are allowed to always
assume the code never does anything that results in undefined behavior and
generate code that is wrong in any number of ways if that assumption fails.
--
... <IXOYE><
