Strange zero variable problem

Forum 2005-2010 (read only) Software Bugs & Suggestions
1

I have found something quite strange, at least to me, in some of my code.

I have a for loop:

for(int i = 0; i < count; i++)

and inside that I assign a variable:

int jump = nameLength + i + 8

where nameLength is set in setup() as a non-zero number;

This code fails at the variable declaration however as soon as I change it to this:

int jump = nameLength + (i+1) + 7

it works perfectly!

Any idea why this happens?

Andy

2

Works fine for me...

int nameLength;
int count;

void setup( void )
{
  nameLength = 13;
  count = 4;
}

void loop( void )
{
for(int i = 0; i < count; i++) 
int jump = nameLength + i + 8;
}

Could this be the problem...

int jump = nameLength + i + 8 ;

3

The semicolon was there, I must have missed it when I copied the code.

Theres actually around 10 more lines of code in the loop before the variable is assigned, and when I use i on it's own, the whole block fails to work:(

It's not really an inconvenience, just peculiar

4

Theres actually around 10 more lines of code in the loop before the variable is assigned, and when I use i on it's own, the whole block fails to work:(

So, show the whole block. There is clearly a problem with the code that needs to be addressed, not masked.

5 
ExtEEPROM ee;
#define disk1 0x50

int slot = 0;
while(ee.readByte(disk1, slot) != 0)
  slot++;
char startArr[6] = "";
for(int i = 0; i < slot; i++)
{
  for(int t = 0; t < 7; t++)
    startArr[t] = (char)ee.readByte(disk1, i+t);
  if(strcmp(startArr, ":Start:") == 0)
  {
    Serial.print("---Start at ");Serial.print(i);Serial.println("---");
    int nameLength = (int)ee.readByte(disk1, i+7);
    char name[nameLength];
    ee.readCharArr(disk1, i+8, nameLength, name);
    Serial.print("Name ");Serial.println(name);
    int noteCount = ee.readByte(disk1, nameLength + (i+1) + 7); //<--where the problem occurs
    Serial.print("Note Count ");Serial.println(noteCount);
  }
}

I am reading data from an external EEPROM chip with a library I have made, that's what ExtEEPROM ee is

6

This code fails at the variable declaration however as soon as I change it

I meant to ask earlier what this means. "fails at the variable declaration"?

7 
for(int t = 0; t < 7; t++)

This loop will execute when t is 0, 1, 2, 3, 4, 5, and 6. That's 7 values.

char startArr[6]

Oops. Not enough room (and no space for the trailing NULL).

if(strcmp(startArr, ":Start:")

The str functions operate on strings, not character arrays. The difference between a character array and a string is that a string is a character array THAT IS NULL TERMINATED. startArr is NOT NULL-terminated.

    char name[nameLength];

Again, no room for the NULL, which you don't add.

8

For some reason, the strcmp was working fine. And also before changing the char array sizes, but some other things, my initial problem has gone away. I was forgetting about this and modifying other code and then came back and tried the original variable declaration and it worked.

Thanks for your help :slight_smile: