Simplest program possible fails

Projects Programming
1

Well, maybe not quite the simplest, but pretty close:

/////////////////////////////////////////////
void setup()
{
Serial.begin(9600);
}

int iLoop = 0;
void loop()
{
if (iLoop++ > 2) return;
Serial.println(iLoop);
delay(500);
}
/////////////////////////////////////////////

prints out:

1
2
3
-32767
-32766
-32765
-32764
-32763
-32762
-32761
...

it's as though it overflows when the >= succeeds. Huh? So confused. Same (very simple) program attached. This is on a Arduino Nano on a DunioKit.

dummy.ino (150 Bytes)

2

Every time through loop, you increment iLoop, regardless if the if() condition is true or false. After doing this 32766 times, iLoop rolls over to -32767 since the range of an int is -32767...32766

3

Ha! Of course! Thanks for the obvious! Is there a way to mark this as the answer? I don't see such a way on the forum but yes, this is definitely the answer.

4 
 if (iLoop++ > 2) return;

Where are you returning to?

5

That would be main(), which calls loop().

6

darrellp:
Ha! Of course! Thanks for the obvious! Is there a way to mark this as the answer? I don't see such a way on the forum but yes, this is definitely the answer.

You can edit the subject of this thread.
Most people just ad [SOLVED] at the start or at the end of the subject.

[SOLVED] Simplest program possible fails

Tom... :slight_smile:
Karma for your consideration.

7

jremington:
That would be main(), which calls loop().

main() calls setup() and then control goes to loop(). Therefore, execution of return instruction in the loop() function should revert the control to the setup() function?

8

GolamMostafa:
main() calls setup() and then control goes to loop(). Therefore, execution of return instruction in the loop() function should revert the control to the setup() function?

You have the source.
Why don't you LOOK?

9

main() calls setup() and then control goes to loop(). Therefore, execution of return instruction in the loop() function should revert the control to the setup() function?

No

The return takes the program back to the point at which loop() was called in main(), not the start of main(), so setup() does not run again

/*
  main.cpp - Main loop for Arduino sketches
  Copyright (c) 2005-2013 Arduino Team.  All right reserved.

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include <Arduino.h>

// Declared weak in Arduino.h to allow user redefinitions.
int atexit(void (* /*func*/ )()) { return 0; }

// Weak empty variant initialization function.
// May be redefined by variant files.
void initVariant() __attribute__((weak));
void initVariant() { }

void setupUSB() __attribute__((weak));
void setupUSB() { }

int main(void)
{
 init();

 initVariant();

#if defined(USBCON)
 USBDevice.attach();
#endif
 
 setup();
    
 for (;;) {
 loop();
 if (serialEventRun) serialEventRun();
 }
        
 return 0;
}
10

UKHeliBob:
The return takes the program back to the point at which loop() was called in main(), not the start of main(), so setup() does not run again

+K for the information and the evidence.