Re: boost::nil

From: deansturtevant_at_[hidden]
Date: 2001-06-13 15:35:32

Is that really true? sizeof(void*) > sizeof(int*) ? On what platform?
Seems to me like that would break a lot of C/C++ code.

--- In boost_at_y..., "Richard Damon" <rdamon_at_b...> wrote:
> By the standard, Vararg functions need to have the null pointer 
constant
> casted to the appropriate pointer type. On systems were all 
pointers are the
> same size you have a better chance of getting away with an uncast 
NULL then
> with 0, as vendors normally try to make it work if they can by 
using 0L if
> that makes it the right size for a pointer, but this is not 
portable. On
> word addressable machines sizeof(void*) > sizeof(int*) so to 
compiler can
> not know at the call site what size null pointer constant to pass.
> 
> --
> Redirector to current best: Richard_Damon_at_i...
> Home: rbrdamon_at_r...
> Work: rdamon_at_B...
> 
> 
> -----Original Message-----
> From: toon [mailto:toon]On Behalf Of Toon Knapen
> Sent: Wednesday, June 13, 2001 11:59 AM
> To: boost_at_y...
> Subject: Re: [boost] boost::nil
> 
> 
> > I disagree.  "int *p = 0" is, and has been, the recommended way of
> > dealing with null pointers in C++ since several years, and I find 
it
> > easily to understand, easier than parsing "NULL".  That's 
certainly
> > a matter of personal taste.
> >
> (I have not seen this mentioned on the list before so here goes)
> 
> I would like to point you to following good info about porting to 
64bit
> :
> 
http://www.tru64unix.compaq.com/linux/compaq_cxx/docs/uguport.htm#inde
x_x_22
> 7
> 
> stating that "Using a 0 where you should use NULL generates a 32-bit
> constant. On Alpha systems, this could yield 0 in the low 32 bits 
and
> useless data in the high 32 bits when passed into a function that
> accepts a variable number of arguments. Using NULL from the 
<stdio.h>
> header file provides the correct value. "
> 
> In 32bit everything works out fine whereas it does not when sizeof
(T*)
> != sizeof(int)
> 
> toon
> 
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