calloc (actually NULL =?= 0)

[Brian Matthews]

John Hascall (hascall at atanasoff.cs.iastate.edu) writes:
|In article <1428 at auspex.auspex.com> guy at auspex.auspex.com (Guy Harris) writes:
|>>According to Harbison + Steele's book, calloc returns a region of
|>>memory with all bits set to zero. They also point out that pointers
|>>I always thought a pointer consisting of zero bits is NULL. 
|>Nope.  No such guarantee was ever made by any C language spec.
|
|   What about the following taken from K&R, Appendix A, section 7.14,
|   "Assignment operator":
|
|       [talking about assigning ints to/from pointers
|       being "a bad thing"] ...
|       However, it is guaranteed that assignment of the
|       constant 0 to a pointer will produce a null pointer...

But this doesn't guarantee that the resulting pointer consists of all
zero bits.  Arbitrary bit fiddling may occur during an assignment
(consider assigning an int to a float, the bits can't be just copied), so
just because you start with all 0 bits doesn't mean you end with all zero
bits.

-- 
Brian L. Matthews  blm at cxsea.UUCP   ...{mnetor,uw-beaver!ssc-vax}!cxsea!blm
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