Re: [Boost-users] boost::any and const pointers

Subject: Re: [Boost-users] boost::any and const pointers
From: Dominique Devienne (ddevienne_at_[hidden])
Date: 2009-12-02 13:24:49

On Wed, Dec 2, 2009 at 10:55 AM, James C. Sutherland
<James.Sutherland_at_[hidden]> wrote:
> int main()
> {
>  Properties p;
>  int i=1;
>  set(p,"int",i);
>  set(p,"int*",&i);
>
>  int*       j = get<int*>(p,"int*");  // I don't want this to compile
>  const int* k = get<int*>(p,"int*");  // I want this to compile fine.
> }
>
> Currently this whole code compiles without trouble, but I don't want to allow a non-const pointer to be extracted.  Any ideas of how to accomplish this?

Thanks not possible AFAIK. The first compiles alright, but will fail
at runtime because the boost::any was constructed using a const int*.
By design all extractions are checked at runtime only, and the
typeid()/std::type_info of what you put in and what you try to get it
as must be the same. Given your code, you can't even do get<int>(p,
"int"), because a const int was put in, not an int (see your set()
impl), and typeid(int) != typeid(const int). --DD