Array of Pointers

This is a discussion on Array of Pointers within the C Programming forums, part of the General Programming Boards category; Can someone tell me how the heck to get input into an array of pointers, via my code. insert Code: ...

  1. #1
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    Array of Pointers

    Can someone tell me how the heck to get input into an array of pointers, via my code.

    insert
    Code:
    #include<stdio.h>
    #include<stdlib.h>
    
    int main()
    {    
    	int granularity, *Arrayptr,iLoop,iCount,iarray;
    	char *arraysize;
    	char szBuf[10];
    		printf("Input the array size: \n");          		     //Ask the user for input		
    		arraysize = fgets(szBuf,sizeof(szBuf), stdin);   	     //Get the input from the user
    		iarray = atoi(arraysize);				             //Convert Input from string to integer
    		Arrayptr = malloc(iarray * sizeof(int));  		         //Reserve some memory on the heap for the array
    	             if((Arrayptr = malloc(iarray * sizeof(int))) == NULL){
                        (void)printf("Malloc failed");
                        return 1;
                     }
            if(Arrayptr != NULL){        
            printf("Please input values into array -1 to quit: \n");
                     for(iLoop = 0 ;; iLoop ++){
                     scanf("%d",Arrayptr[iLoop]);
                     iCount += Arrayptr[iLoop];
                     }
            }                            
    return 0;
    }
    I'm trying to use scanf but it's not working, then I want to take the value entered and keep a running total, I'm just not sure why it's not working.

    Thanks

    Andrew

  2. #2
    and the hat of wrongness Salem's Avatar
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    > Arrayptr = malloc(iarray * sizeof(int)); //Reserve some memory on the heap for the array
    > if((Arrayptr = malloc(iarray * sizeof(int))) == NULL)
    Only call it once, then check for NULL

    > if(Arrayptr != NULL)
    You already checked for NULL, checking again adds nothing.

    > for(iLoop = 0 ;; iLoop ++)
    When does this loop exit?

    > scanf("%d",Arrayptr[iLoop]);
    You still need the &, as in
    scanf("%d", &Arrayptr[iLoop]);
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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  3. #3
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    Okay so I put the exit condition to iLoop <= iarray or in other words when the array size has been reached then exit.

    When I enter say
    2
    2
    2
    2
    2
    2
    2
    2
    etc...... up to 10 times the value returned by iCount seems to be 2008858765, I'm sure why I'm getting this return value.

  4. #4
    Frequently Quite Prolix dwks's Avatar
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    Initialize (or set) iCount to zero. Right now it starts with a "random" value.
    dwk

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