Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.std.c++ > #105

Re: To standardize Boost.Pool

Show all headers | View raw

On 4/14/2011 12:10 PM, Phil Bouchard wrote:

>
> is_from() actually invokes undefined behavior if its parameter is a
> pointer referring to an element outside of the pool according to 5.7.6.
> If the pointer was to be casted to the largest integer type available
> on the system then a range check would be valid for that system. For
> example:
>
> bool is_from(const char* p)
> {
> return reinterpret_cast<long>(buffer)<= reinterpret_cast<long>(p)&&
> reinterpret_cast<long>(p)< reinterpret_cast<long>(buffer + sizeof(buffer));
> }
>
> It's "implementation defined" but perhaps a reinterpret_cast of a
> pointer to a long integer could be guaranteed to be valid by the
> standards, long being the greatest integer available on a system.
>

It turns out the C standard defines intptr_t to be the same size as a
pointer (7.18.1.4).  The following would consequently be perfectly portable:

bool is_from(const char* p)
{
   return reinterpret_cast<intptr_t>(buffer)<=
reinterpret_cast<intptr_t>(p)&&
reinterpret_cast<intptr_t>(p)< reinterpret_cast<intptr_t>(buffer +
sizeof(buffer));
}


Regards,
-Phil


-- 
[ comp.std.c++ is moderated.  To submit articles, try posting with your ]
[ newsreader.  If that fails, use mailto:std-cpp-submit@vandevoorde.com ]
[              --- Please see the FAQ before posting. ---               ]
[ FAQ: http://www.comeaucomputing.com/csc/faq.html                      ]

Back to comp.std.c++ | Previous | Next — Previous in thread | Next in thread | Find similar

Thread

To standardize Boost.Pool  Phil Bouchard <phil@fornux.com> - 2011-04-12 13:10 -0600
  Re: To standardize Boost.Pool Phil Bouchard<phil@fornux.com> - 2011-04-14 13:10 -0600
    Re: To standardize Boost.Pool  Phil Bouchard <phil@fornux.com> - 2011-04-14 17:18 -0600
      Re: To standardize Boost.Pool  "Bo Persson" <bop@gmb.dk> - 2011-04-17 01:33 -0600

csiph-web