pointer int math wrong

This is a discussion on pointer int math wrong within the C Programming forums, part of the General Programming Boards category; ive been having alot of fishy problems lately if i run this it adds the numbers wrong. i tried adding ...

  1. #1
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    Jul 2002
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    pointer int math wrong

    ive been having alot of fishy problems lately

    if i run this it adds the numbers wrong. i tried adding a * to it but it didnt help any.

    Code:
    int main() {
    	int x = 1;
    	
    	test(x);
    	
    	return 0;
    }
    
    int test(int *x) {
    	printf("X = %i\n", x);
    	++x;
    	printf("X Now = %i", x);
    	
    	return 0;
    }
    i get back
    X = 1
    X Now = 5
    i want
    X Now = 2

  2. #2
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    You have a few problems with your code. Here is what it should look like.

    Code:
    #include <stdio.h>
    
    int test( int *x );
    
    int main() {
    	int x = 1;
    	
    	test(&x);
    	
    	return 0;
    }
    
    int test(int *x) {
    	printf("X = %i\n", *x);
    	++(*x);
    	printf("X Now = %i", *x);
    	
    	return 0;
    }
    When you pass a regular variable to a function as a pointer you need to pass the address of it. Also you have to dereference the pointer to get the value located there. Hope this helps.

    EDIT: I don't know how it even compiled for you. There are several errors that should occur. If you just print out x in the test function without dereferencing you will get the address not the value.

  3. #3
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    i didnt get why it compiled either, it didnt seem right. but how can 1 be the adress? i thought they took a completly diff form(i was thinking hex) and wouldnt my kernel take up alot of the begining?

    thanks

  4. #4
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    i just compiled your code, seg fault.

    now im really confused.

  5. #5
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    What compiler are you using??

  6. #6
    End Of Line Hammer's Avatar
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    Originally posted by mart_man00
    i just compiled your code, seg fault.

    now im really confused.
    Did you cut/paste the code, or re-type it?
    When all else fails, read the instructions.
    If you're posting code, use code tags: [code] /* insert code here */ [/code]

  7. #7
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    i copy and pasted it into vi, but instead of typing :q i had caps on and did :Q. sorry

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