Possible bug after using sprintf function

rbhatia · **Joined:** Mon Jul 25, 2011 4:15 pm **Posts:** 64

Hi,

Code:

// network variables
// destination is to all nodes
char aux[0];
int counterProblem = 0;

void setup()
{
  RTC.ON();
  // 2011, dec, 19, sunday, 6 pm, 00 min, 00 sec
  RTC.setTime( 2011, 12, 19, 2, 18, 0, 0 );
  ACC.ON();
  USB.begin();
  
  counterProblem = 0;
}

void loop()
{
  USB.print("counterProblem=");
  USB.println(counterProblem);
  sprintf(aux,"%d,%d,%d,temp:%d,bat:%d%c%c%c",
          ACC.getX(), ACC.getY(), ACC.getZ(), 
          RTC.getTemperature(), PWR.getBatteryLevel(),'%','\r','\n');
  USB.print("counterProblem=");
  USB.println(counterProblem);
  counterProblem++;
  if (counterProblem > 10)
  {
    USB.println("counterProblem is > 10");
    counterProblem = 0;
  }
  delay(1000);
}

The above code will print out the integer counterProblem at the beginning of the loop and after the sprintf function. The values printed will be 0 and 14000 respectively. Why is this happening?

rbhatia · **Joined:** Mon Jul 25, 2011 4:15 pm **Posts:** 64

I could call the counterProblem integer anything and it will somehow be increased by 14000 by the sprintf function. I tried using just sprintf without the RTC, ACC, and the PWR and the same result occurs except there is less of an increase to my integer...

libelium-dev · **Joined:** Mon Sep 28, 2009 1:06 pm **Posts:** 7479

Dear rbhatia,

Looking at your code we see two issues:

1 - why you define char aux[0]? You should define it as longer as your frame is, or using calloc as follows:

Quote:

char * aux;
aux = (char) calloc(length,sizeof(char));

(...)

free = aux;
aux=NULL;

2 - I noticed that as you say, there is some trouble using sprintf in your way, try to directly insert the end characters as follows and it will works.

Quote:

sprintf(aux,"%d,%d,%d,temp:%d,bat:%d%\r\n",ACC.getX(), ACC.getY(),ACC.getZ(),RTC.getTemperature(), PWR.getBatteryLevel());

Kind regards.

rbhatia · **Joined:** Mon Jul 25, 2011 4:15 pm **Posts:** 64

Hi libelium-dev,

The spaces between the commas in the sprintf function was the root of the problem. I find this very strange... Anyway, at least it's fixed. I changed the statement for the aux variable to "char* aux" like you said but the other statement:

aux = (char) calloc(length,sizeof(char));

Doesn't work because of length is a missing function.. unless I was supposed to replace length with the length of my aux. It works fine without that statement either.

Thanks,
Ronak

rbhatia · **Joined:** Mon Jul 25, 2011 4:15 pm **Posts:** 64

Oh I just figured it out.

Code:

char* aux;
..
aux = (char*) calloc(25,sizeof(char*));

This works when I use:

Code:

aux = get_file();

Code:

*char get_file()

libelium-dev · **Joined:** Mon Sep 28, 2009 1:06 pm **Posts:** 7479

Hi,

Yes, that's right. Sorry about the typo. It is correct this way:

Quote:

char * aux;
aux = (char*) calloc(length,sizeof(char));

(...)

free = aux;
aux=NULL;

Bets regards