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Assigning NULL to a variable (not pointer)

I remember that this is a bad practice, but can not find a definitive
resource that states it is bad and why. Can anyone help?

Oct 16 '06
31 17720
"Ron Natalie" <ro*@spamcop.ne twrote in message
news:45******** **************@ news.newshostin g.com...
Jim Langston wrote:
>>
int MyVar = NULL;

I would immediatly presume that MyVar is being cast to a pointer
somewhere and is not acutally used as an integer. And I would start
reading the code with that in mind.

There's no guarantee that a int reinterpret_cas ted to a pointer yields
a null pointer value. You get only two guarantees:

1. A integer constant expression of value zero converts to a null
pointer.

2. A pointer value can be converted to a sufficiently large integer
(if such exists) and back to the original pointer type without
change.
I agree to that, yet I still see unsigned long ints used as pointers in some
code written for Windows.
Oct 17 '06 #31
Jim Langston wrote:
>
I agree to that, yet I still see unsigned long ints used as pointers in some
code written for Windows.

Windows has a type for that actually. They call it DWORD_PTR
which took me a while to realize it isn't a poitner to a DWORD
but a integral type that's big enough to hold either a DWORD
or a pointer. Microsoft had to chase down these when they
went to x64 because they were using DWORD (32 bits) to hold
pointers all over the place in the hideous windows message system.
Oct 17 '06 #32

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