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Problem with NULL

Started by TheRealBartman Apr 27, 2003 at 6:53 PM 16 replies 2.3k views

Original Post

Apr 27, 2003 at 6:53 PM

Sometimes, almost at random, some of the files in my projects give me errors about NULL being undefined, while other files compile just fine. Why is this, and is there anyway to fix it without doing #define NULL 0x000000 in every affected source file? Thanks, Michael Bartman

Gee

Apr 27, 2003 at 7:09 PM

Well NULL is not a C nor a C++ keyword, so of course you need to define it. Just include stdio, iostream, windows.h and NULL will ultimately be defined...

---
General Programmer at Wildfire Games
working on the 0 A.D. project

Beer Hunter

122

Beer Hunter

Apr 27, 2003 at 7:34 PM

#includeany of <clocale>, <cstddef>, <cstdio>, <cstdlib>, <cstring>, <ctime>, <cwchar>.

Arild Fines

138

Arild Fines

Apr 27, 2003 at 7:37 PM

Or use 0...

"Laughter means distance. Where laughter is absent, madness begins. The moment one takes the world with complete seriousness one is potentially insane. The whole art of learning to live means holding fast to laughter; without laughter the world is a torture chamber, a dark place where dark things will happen to us, a horror show filled with bloody deeds of violence."
-- Jens Bjørneboe

TheRealBartman

Author

TheRealBartman

Apr 27, 2003 at 8:53 PM

Thanks for the replies

I would just use 0, and even though it is shorter to write than NULL, I am more partial to using NULL.

It is just a preference of mine.

Michael Bartman

Irrelevant

Apr 27, 2003 at 8:58 PM

Your preference is wrong.

zealouselixir

157

zealouselixir

Apr 27, 2003 at 9:17 PM

NULL has a standard value, according to the C++ standard. But, the implementation is still responsible for defining it in a standard manner. I personally use 0 to indicate null-ness. One might think that NULL helps clarify that it''s actually a null pointer, but in my experience, it doesn''t.

Later,
ZE.

//email me.//zealouselixir software.//msdn.//n00biez.//
m i s c e l l a n e o u s l i n k s

RhoneRanger

Apr 28, 2003 at 12:32 AM

Okay, let me start it.....

Is NULL different than 0?

Techlead
www.myran.com/enilno

Zipster

511

Zipster

Apr 28, 2003 at 12:34 AM

0 isn''t typesafe? What?

Beer Hunter

122

Beer Hunter

Apr 28, 2003 at 1:03 AM

quote:
Original post by Anonymous Poster
The 0 or NULL argument. Run! Oh... and neither is typesafe.

Joking, I assume?

Ready4Dis

Apr 28, 2003 at 1:05 AM

quote:
Original post by RhoneRanger
Okay, let me start it.....

Is NULL different than 0?

Techlead
www.myran.com/enilno

I don''t beleive NULL is allowed to be anything besides 0, but don''t hold me to that, as it may be up to the implementation to decide. In any compiler/platform I''ve EVER seen, NULL has always been defined as 0.

Chris-

Apr 28, 2003 at 1:30 AM

quote:
Original post by Ready4Dis
[quote]Original post by RhoneRanger
Okay, let me start it.....

Is NULL different than 0?

Techlead
www.myran.com/enilno

I don't beleive NULL is allowed to be anything besides 0, but don't hold me to that, as it may be up to the implementation to decide. In any compiler/platform I've EVER seen, NULL has always been defined as 0.

in the C standard, NULL is (void *)0
in the C++ standard, NULL is 0

When programming in C++, Bjarne says NULL is naughty, stick to trusty 0.

[edited by - Chris- on April 28, 2003 2:31:33 AM]

TheRealBartman

Author

TheRealBartman

Apr 28, 2003 at 1:45 AM

Argh lol,

Okay, I won''t use NULL anymore.

Why did it come about, anyway?

Michael Bartman

RhoneRanger

Apr 28, 2003 at 1:48 AM

null is (void*) 0, which is different than just
''0''

''0'' still is a number, while NULL literally nothing!

Peon

102

Peon

Apr 28, 2003 at 1:57 AM

Interesting thread, I had no idea. I always used NULL; looks like it''s time to change my ways

Cedric

Apr 28, 2003 at 2:04 PM

quote:
Original post by RhoneRanger
null is (void*) 0, which is different than just
''0''

null is not Standard C++. NULL is 0.

Cédric

PHRICTION

Apr 28, 2003 at 4:28 PM

Quoth Stroustrup:

In C, it has been popular to define a macro NULL to represent the zero pointer. Because of c++''s tighter type checking the use of plain 0, rather than any suggested NULL macro, leads to fewer problems. If you feel you must define NULL, use

const int NULL = 0;

The const qualifier prevents accidental redefinition of NULL and ensures that NULL can be used where a constance is required.

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