Re: Re: Re: boost.function with CW 8.2 on W2k

10 Sep 2002

      "Douglas Gregor"  schrieb im Newsbeitrag news:200209100949.40416.gregod@cs.rpi.edu...
...
On Tuesday 10 September 2002 08:29 am, Bertolt Mildner wrote:
...
[...]
...
I have tried to make nonnull() inline and/or static but that didn't help.
I think the root of the problem is that the address of nonnull() is
taken. I wonder if it is really needed to return a real (member) function
pointer or if it would be OK to just return (safe_bool)1 ?
Don't know if this is useful but at least it makes my compiler more happy
[snip]
...
{ return (this->empty())? 0 : (safe_bool)~0; }
      { return (this->empty())? (safe_bool)~0 : 0; }
Unfortunately, that invokes implementation-defined behavior, because 
(safe_bool)~0 may or may not be the null pointer. 
[...]
Is really only a valid (member) function pointer guaranteed to be non-null?
I think it is very strange that ~0 may not be non-null!

I have tried this one:

diff -r1.33 function_base.hpp
267a268,275
...
namespace detail
  {
    inline void nonnull()
    {
    }
  }
274c282
<     bool empty() const { return !manager; }
---
...
inline bool empty() const { return !manager; }
284c292
<     operator bool () const { return !this->empty(); }
---
...
inline operator bool () const { return !this->empty(); }
287,291c295
<     struct dummy {
<       void nonnull() {};
<     };
< 
<     typedef void (dummy::*safe_bool)();
---
...
typedef void (*safe_bool)();
294,295c298,299
<     operator safe_bool () const 
<       { return (this->empty())? 0 : &dummy::nonnull; }
---
...
inline operator safe_bool () const 
      { return (this->empty())? 0 : &detail::nonnull; }
297,298c301,302
<     safe_bool operator!() const
<       { return (this->empty())? &dummy::nonnull : 0; }
---
...
inline safe_bool operator!() const
      { return (this->empty())? &detail::nonnull : 0; }
*but*, now I get the following errors:

Error   : call of non-function
 (instantiating: 'boost::function1>>>, std::vector>, std::allocatorboost::function_base>::function1>>>, std::vector>, boost::shared_ptrFct::Crypto::Engine, std::allocatorboost::function_base>>(boost::function2>>>, std::vector>, boost::shared_ptrFct::Crypto::Engine, std::allocatorboost::function_base>)')
  (instantiating: 'boost::function1>>>, std::vector>, std::allocatorboost::function_base>::assign_to>>>, std::vector>, boost::shared_ptrFct::Crypto::Engine, std::allocatorboost::function_base>>(boost::function2>>>, std::vector>, boost::shared_ptrFct::Crypto::Engine, std::allocatorboost::function_base>)')
   (instantiating: 'boost::function1>>>, std::vector>, std::allocatorboost::function_base>::assign_to>>>, std::vector>, boost::shared_ptrFct::Crypto::Engine, std::allocatorboost::function_base>>(boost::function2>>>, std::vector>, boost::shared_ptrFct::Crypto::Engine, std::allocatorboost::function_base>, boost::detail::function::function_obj_tag)')
    (instantiating: 'boost::detail::function::function_obj_invoker1>>>, std::vector>, boost::shared_ptrFct::Crypto::Engine, std::allocatorboost::function_base>, boost::shared_ptr>>>, std::vector>>::invoke(boost::detail::function::any_pointer, std::vector>)')
function_template.hpp line 110             return (*f)(BOOST_FUNCTION_ARGS);

Error   : call of non-function
 (instantiating: 'boost::detail::function::function_obj_invoker1>>>, std::vector>, boost::shared_ptrFct::Crypto::Engine, std::allocatorboost::function_base>, boost::shared_ptr>>>, std::vector>>::invoke(boost::detail::function::any_pointer, std::vector>)')
function_template.hpp line 110             return (*f)(BOOST_FUNCTION_ARGS);

Bertolt

-- 
Free Crypto Token - FCT
www.FreeCryptoToken.org