pointer initializatin - where to put the asterisk?

This is a discussion on pointer initializatin - where to put the asterisk? within the C Programming forums, part of the General Programming Boards category; Hello there! I am puzzled by a question lately, to wich I can't find an answer. What is the difference ...

  1. #1
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    Question pointer initializatin - where to put the asterisk?

    Hello there!
    I am puzzled by a question lately, to wich I can't find an answer. What is the difference between the next pointer initialization methods:

    Code:
    int* pointer_name=NULL
    and

    Code:
    int *pointer_name=NULL
    I undestand, that the second one is the "standard" way of initializing a pointer, or at least that is how the tutorial on this website shows it, but what does the first one mean?

    As I was searching the web for answers, I found another interesting example, where the pointer was initialized like this:

    Code:
    int * pointer_name=NULL
    This was supposed to have some sort of special meaning, but I did not quite understand it, and I can't find the website now for further studying. I would be glad if someone could explain to me all these things about pointer initialization.

    Big thanks in advance for everyone, reading this.

  2. #2
    Woof, woof! zacs7's Avatar
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    They mean exactly the same thing, it's a matter of style. I prefer the third one personally.

  3. #3
    ... kermit's Avatar
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    Just keep in mind that doing

    Code:
    int* p1, p2;
    Does not declare two pointers, as if int* was a new type declaration. You could use a typedef to make an alias if you wanted to, but that is another story. If you want to declare two pointers, you have to do something like this:

    Code:
    int* p1, *p2;
    or

    Code:
    int* p1, * p2;
    Whatever you end up doing, try to be consistent in your use of it.

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    Question Well, here's an example...

    Hm... I am trying to understand how does the next function works. It is from a SDL game programming tutorial.

    Code:
    SDL_Surface *load_image(char filename[])
    	{
    	SDL_Surface* loadedImage=NULL;
    	SDL_Surface* optimizedImage=NULL;
    
    	loadedImage=SDL_LoadBMP(filename);
    	if(loadedImage!=NULL)
    		{
    		optimizedImage=SDL_DisplayFormat(loadedImage);
    		SDL_FreeSurface(loadedImage);
    		}
    	return optimizedImage;
    	}
    As you can see, both methods are used in this function definition - but why? Is this really just a matter of style or does it make some crucial difference if I put the asterisk to another position? As far as I tested, the program runs and compiles fine, when I play around with the asterisks, so - can it be, that the author of the tutorial wasn't consistent enough?

    Thanks for the answers so far!

  5. #5
    C++まいる!Cをこわせ!
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    http://www.research.att.com/~bs/bs_faq2.html#whitespace
    Bjarne "explains" the difference between the two styles.
    I prefer the first one, and find the 3rd one acceptable, as well.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  6. #6
    spurious conceit MK27's Avatar
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    I like the 2nd one because it makes the most sense, and you can consider it the same as dereferencing
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
    The C Book -- nice online learner guide
    Current ISO draft standard
    CCAN -- new CPAN like open source library repository
    3 (different) GNU debugger tutorials: #1 -- #2 -- #3
    cpwiki -- our wiki on sourceforge

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    Thumbs up Thanks a lot!

    Now, that is the kind of answer I was looking for! Thanks a lot everyone, for helping me out!

  8. #8
    C++まいる!Cをこわせ!
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    Quote Originally Posted by MK27 View Post
    I like the 2nd one because it makes the most sense, and you can consider it the same as dereferencing
    The second one makes absolutely no sense to me, whatsoever...
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  9. #9
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by laczfinador
    can it be, that the author of the tutorial wasn't consistent enough?
    Yes, there is a minor inconsisteny in style there.
    C + C++ Compiler: MinGW port of GCC
    Version Control System: Bazaar

    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  10. #10
    ... kermit's Avatar
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    Quote Originally Posted by Bjarne Stroustrup
    placing the * closer to the name does not make this kind of error significantly less likely.
    I disagree, but will grant that obviously my opinion as a programmer matters very little compared to someone as experienced as Stroustrup. That said, when I see

    Code:
    double *p, q;
    it is immediately obvious to me that p is the pointer, and q is just a double.* For the original poster, seeing as you are posting this on the C board, have a look at this and this from the comp.lang.c FAQ. Steve Summit acknowledges the difference of opinion of the C FAQ and Stroustrups C++ FAQ.

    I think Stroustrup makes a good point about declaring each pointer one per line. Again, whichever style one chooses, it is good to be consistent.

    * - I would add that I am undoubtedly biased by the fact that C is the first language I learned and though I dabble in other languages (most recently I have taken up the task of becoming competent in C++ programming) it is still my 'primary' language. I have also gotten used to K&R style. Had I learned C++ first, I guess I would probably be more inclined to the 'Stroustrup style' of declaring a pointer with the asterisk next to the type rather than the name...
    Last edited by kermit; 01-18-2009 at 12:31 PM.

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