Re: [Boost-users] [serialize] struct save_array_type in oserializer.hpp

From: Oleg V. Zhylin (ovz_at_[hidden])
Date: 2007-04-12 09:08:30

At least for VC7.1 compiler

  int a, b;

  cout<<typeid(sizeof(a)/(a - b)).name()<<endl;

 prints "unsingned int" and issues no warnings about int -> size_t
conversion. Thus I still wonder if usage of int type in 

> >         int count = sizeof(t) / (
> >             static_cast<const char *>(static_cast<const void
> *>(&t[1]))

dictated by consideration for some other C++ compiler. VC7.1 does issue
a warning

warning C4267: 'initializing' : conversion from 'size_t' to 'int',
possible loss of data

for that code. I would suggest to consider either change type of
variable count from int to size_t or disable C4267 for this piece of
code for MS compilers.

--- Ovanes Markarian <om_boost_at_[hidden]> wrote:

> 
> On Wed, April 11, 2007 17:51, Oleg V. Zhylin wrote:
> > Hi,
> >
> >   Is there a reason to use type int in the code at line 487 in
> > oserializer.hpp?
> >
> >         int count = sizeof(t) / (
> >             static_cast<const char *>(static_cast<const void
> *>(&t[1]))
> >
> >             - static_cast<const char *>(static_cast<const void
> > *>(&t[0]))
> >
> >   C++ standard draft states in section 5.3.3 [expr.sizeof]
> >
> > The result is a constant of an implementation-defined
> > type which is the same type as that which is named
> > size_t in the standard header <cstddef>(18.1).
> 
> 
> I assume otherwise you will get a warning, that a sign can be lost
> through the assignment. The
> problem here is that expression (type* - type*) results not in an
> unsigned type (size_t) but a
> signed difference type. If you divide unsigned value through a signed
> value you get a signed
> value. And then you would (according to your suggestion) assign it to
> an unsigned value =>
> warning.
> 
> 
> 
> With Kind Regards,
> 
> Ovanes Markarian
> 
> _______________________________________________
> Boost-users mailing list
> Boost-users_at_[hidden]
> http://lists.boost.org/mailman/listinfo.cgi/boost-users
> 

WBR Oleg V. Zhylin   ovz_at_[hidden]

       
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