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Strange code results using an array [solved]

 
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/dev/human



Joined: 01 Sep 2008
Posts: 19
Location: Earth / Europe / Germany

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Strange code results using an array [solved]
PostPosted: Wed Apr 22, 2009 11:03 pm     Reply with quote

Hi All

I programmed a simple piece of code to handle a simple stack.

Code:

   float32 TemppH;
   float32 TempT;
   int loop;

   StackHnd (0, 0, Clear);
   for (loop = 0; loop < 20; loop++) {
      TempT = loop+1;
      TemppH = loop+1;
      StackHnd (&TemppH, &TempT, Push);
   }


int StackHnd (float32* pH, float32* T, int Cmd) {

   static int StackPntr = 0;
   float32 phStack [Stacksize];
   float32 TStack [Stacksize];
   
   switch (Cmd) {
      case Clear:
         for (StackPntr = 0; StackPntr < Stacksize; StackPntr++) {
            pHStack [StackPntr] = 0.0;
            TStack [StackPntr] = 0.0;
         }
      break;
     
      case Push:
         for (StackPntr = 1; StackPntr < Stacksize; StackPntr++) {   // Top of stack is "StackSize", bottom is 0
            phStack [StackPntr -1] = phStack [StackPntr];            // Push all pH values down
            TStack [StackPntr -1] = TStack [StackPntr];              // Push all temp values down
         }
         pHStack [StackSize-1] = *pH;                                // Put actual value on top
         TStack [StackSize-1] = *T;                                  // Put actual value on top
      break;
     
      case Calc:
      break;
     
      default:
     
   }
   return 0;
}


This piece does not seem to difficult to me but checking the stack I do see:

Quote:

pHStack: (2.172,3.000,4.000,5.000,6.000,7.000,8.000,9.000,10.000,11.000)
TStack: (2.000,3.000,4.000,5.000,6.000,7.000,8.000,9.000,10.000,11.000)

Any ideas for pHStack [0] Question

Thanks in advance!
_________________
Never check your brain at the door!


Last edited by /dev/human on Thu Apr 23, 2009 10:51 pm; edited 1 time in total
FvM



Joined: 27 Aug 2008
Posts: 2337
Location: Germany

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PostPosted: Wed Apr 22, 2009 11:30 pm     Reply with quote

The problem could be traced, if you had provided complete code, but you preferred not to do.

I guess, that phStack is overwritten, cause it's not declared static. Can be easily checked in the projects *.sym file. Generally, the compiler can be expected (respectively is required) to overlay phStack with other variables outside the function, to save RAM space.
/dev/human



Joined: 01 Sep 2008
Posts: 19
Location: Earth / Europe / Germany

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PostPosted: Thu Apr 23, 2009 10:51 pm     Reply with quote

Thanks, stupidly blind. The ram space was actually used by another var.

... and yeah, I actually preferred not to send the remaining about 564 lines of code. Very Happy
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