Dynamic Array

firetheGlazer · 07-11-2008, 09:56 AM

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

tabstop · 07-11-2008, 10:08 AM

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

Also: do you change maxIndex after you realloc?

firetheGlazer · 07-11-2008, 10:35 AM

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

tabstop · 07-11-2008, 10:36 AM

Quote:

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.

firetheGlazer · 07-11-2008, 11:57 AM

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?

07-11-2008, 10:08 AM	#2
tabstop and the Hat of Guessing Join Date: Nov 2007 Posts: 8,831	What do you mean by "there aren't any structs"? Also: do you change maxIndex after you realloc?
tabstop is offline

07-11-2008, 10:35 AM	#3
firetheGlazer Registered User Join Date: Jun 2008 Location: Northern Va Posts: 18	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
firetheGlazer is offline

07-11-2008, 11:57 AM	#5
firetheGlazer Registered User Join Date: Jun 2008 Location: Northern Va Posts: 18	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?
firetheGlazer is offline

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Dynamic Array Resizing	dld333	C++ Programming	13	11-04-2005 12:13 AM
need help with dynamic array syntax	soldyne	C Programming	3	10-11-2005 01:59 PM
Class Template Trouble	pliang	C++ Programming	4	04-21-2005 04:15 AM
2D dynamic array problem	scsullivan	C Programming	3	12-30-2002 10:02 PM
Dynamic array allocation and reallocation	purple	C Programming	13	08-01-2002 11:48 AM