[boost] Re: safe_dereference()

From: Hillel Y. Sims (hsims_at_[hidden])
Date: 2002-09-04 11:11:28

"Anthony Williams" <anthwil_at_[hidden]> wrote in message
news:15733.50724.159000.285126_at_gargle.gargle.HOWL...
> David B. Held writes:
>  >     // Requirements:
>  >     //   T must be default-constructible
>  >     template <typename T>
>  >     T const& safe_dereference(T* p)
>  >     {
>  >         return p ? *p : T();
>  >     }
>  >
>
> I can see the point, but this is undefined behaviour --- you are returning
a
> reference to a temporary, which as gone out of scope.
>

Why is it ok to say

   int main()
   {
       const string& s = func();
       cout << s << endl;
   }

when func is defined as
   string func() { return string("hello"); }

but then not ok if func is
   const string& func() { return string("hello"); } ?

Is it not possible for a compiler to bind the temporary directly to the
const & in both cases?

hys
--
Hillel Y. Sims
FactSet Research Systems
hsims AT factset.com