Thread: Dynamic Array

Hi. I'm working with dynamic arrays to construct a histogram. I've got an array of pointers to my histogram struct and I try to malloc() and then realloc() the array as necessary. Here's some of the code:

Code:

   typedef struct{
      double val;
      int freq;
      }hPoint;
...
...
...

hPoint **momentBin;
momentBin = (void *)malloc(sizeof(hPoint *) * 10);int maxIndex =10;

...

found=0;
         for(k=0;k<maxIndex;k++)
            {
            if(momentBin[k]==NULL)
               break;
            test =(momentBin[k])->val;
            if (test==bN)
               {
               found =1;
               (momentBin[k])->freq++;
               break;
               };
            
            }
         if(found ==0)
            {
            probCounter++;
            //increase the size of the array
            if (probCounter>=maxIndex)
               {
               hPoint **newArr = realloc(momentBin, maxIndex*2);
               if (newArr==NULL)
                  {
                  printf("Reallocation Error");exit(0);
                  }
               else momentBin = newArr;
               };
            hPoint *temp =(hPoint *) malloc(sizeof(hPoint));
            temp->val=bN;
            temp->freq=1;
            momentBin[probCounter] = temp;

This would be great, except when I loop through my array, there aren't any structs. Your help is greatly appreciated.
Thanks

What do you mean by "there aren't any structs"?

Also: do you change maxIndex after you realloc?

I have a looping statement to read through all of the array:

Code:

for(j=0;j<maxIndex;j++)
         {
         if(momentBin[j]==NULL)
            break;
         test =(momentBin[j])->val;
         printf("%lf\n",test);
         }
printf("Last J: %d",j);

I changed the max index thing to update, but when I run, it still reads j=0

Originally Posted by firetheGlazer

I have a looping statement to read through all of the array:

Code:

for(j=0;j<maxIndex;j++)
         {
         if(momentBin[j]==NULL)
            break;
         test =(momentBin[j])->val;
         printf("%lf\n",test);
         }
printf("Last J: %d",j);

I changed the max index thing to update, but when I run, it still reads j=0

Just because you didn't put anything in 0, doesn't mean you didn't put anything in 1, or 4, or 11, or .... IOW: use continue instead of break.

Wow, okay thanks for the catch. When I put in a continue, GDB spit out my assignment line with a segfault:

Code:

Program received signal SIGSEGV, Segmentation fault.
0x00401758 in main () at Z:\VortexStuff\Moment\moment.c:169
169	         test =(momentBin[j])->val;

I thought that my null test would have caught that. Any thoughts?