Mail Archives: djgpp-workers/1998/03/25/09:54:56
> Date: Wed, 25 Mar 1998 13:33:25 +0100
> From: Vik Heyndrickx <Vik DOT Heyndrickx AT rug DOT ac DOT be>
> Subject: Re: NULL redefined! :(
> Salvador Eduardo Tropea (SET) wrote:
> > But perhaps we must investigate if the __null have some advantage and:
> >
> > 1) Define NULL conditionally (no redefinition)
> > 2) If not defined:
> > a) Test the gcc version, if 2.8.0 define with __null
> > b) if prior define with 0.
>
> Conditional redefinition is dangerous since this way NULL might get two
> values that do not compare equal, even when compiled with the same
> compiler version.
> An unconditional #define is best (i.e. preceded with #undef) as it only
> disadvantages programs which are at fault.
>
> Checking whether gcc's version is 2.8.0, won't help a bit:
> for instance the libc library can have been defined using gcc-2.7.2.1
> and hence NULL would be 0. A program compiled with 2.8.0 would then
> define NULL as __null. Like DJ mentionned, a library function like fopen
> can return NULL (=0) and it must be possible that a program compares it
> with NULL (=__null).
>
I suggest to copy definition of NULL to .h files that conflicts
with ones from gcc 2.8.0 (%DJDIR%/lang/cxx/libio.h vai
%DJDIR%/lang/cxx/streambuf.h)
-------------------------------------------------------
#ifndef NULL
# if defined __GNUG__ && \
(__GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 8))
# define NULL (__null)
# else
# if !defined(__cplusplus)
# define NULL ((void*)0)
# else
# define NULL (0)
# endif
# endif
#endif
-------------------------------------------------------
I did so and don't have any problems yet.
Andris Pavenis
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