Definition of NULL. (fwd)

[Jonathan Larmour]

Joel Sherrill wrote:
> 
> An RTEMS user recently noticed that the newlib definitions of NULL are not
> proper.  The proper definition is apparently "0" or "(void *)0".  The
> offending definitions are in:
> 
> stdio.h:#define NULL    0L
> stdlib.h:#define NULL 0L
> string.h:#define NULL 0L
> time.h:#define  NULL    0L
> 
> In newlib/libc/include.  There may be others in machine and OS specific
> files.

Even more interestingly, the "one true" definition is in stddef.h. This is
because if you have included this file from c++ sources, using g++, then you
actually want the definition to be g++'s internal symbol __null. This is all
wrapped up in stddef.h.

So I think that in addition to changing these instances to (void *)0 (which
is the most correct) anyway, we should also #define __need_NULL before
including <stddef.h> so that we pick up the compiler's idea of NULL if
possible.

Jeff?

Jonathan L.
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