Re: [Mingw-users] access violation on static nonst

[K. F. <kfr...@gm...>]

Hi woyt.a!

On Fri, Feb 8, 2013 at 6:30 PM,  <wo...@wp...> wrote:
> Hi,
>
> following code:
> ...
>     static const size_t val1 = 0;
>
>     // causes access violation errof on runtime
>     size_t* pVal1 = const_cast<size_t*>(&val1);
>     *pVal1 = 7;
> ...
>
> can change value of val0 const variable but invokes segmentation fault for val1.
> This is known issue, as val1 is put in the read-only memory page.
>
> My question is:
> 1. is there any way to change static cont variable value?

I'm not certain of this, but I believe that the standard does permit val1 to be
read-only.  If so, then there is no portable way to change a static const
variable.  I don't believe that the standard requires static const to be forced
to be read-only (but I could be wrong).  If so, a compiler might let you
change it, or maybe there's a compiler setting that would let you change
it.  (But I would expect not.)

Perhaps someone more knowledgeable about the standard could give
us a more authoritative (and correct) answer.

> 2. is there any way to prevent compller to put that variable in read-only memory?

Not that I'm aware of, but again, maybe a specific compiler offers some
kind of setting to control this behavior.

If I were doing this, I would not declare the variable const.  (Or not
declare it static, etc.)

(If this is a real use case you're facing, I'm sure we could figure out
an adequate alternative.)

> Regards,
> woyt.a


Good luck.


K. Frank