Thread: why doesn't this work (confused)

I have an
int rownum //which is globally defined

in main I have

Code:

  rownum = 0;
  test[0][0] = '[';
  test[0][1] = '1';
  test[0][2] = '7';
  test[0][3] = ']';
  test[0][4] = '\0';
  test[1][0] = 'b';
  test[1][1] = 'y';
  test[1][2] = 'w';
  test[1][3] = '\0';
  test[2][0] = 'r';
  test[2][1] = 'g';
  test[2][2] = 'b';
  test[2][3] = '\0';
  test[3][0] = 'r';
  test[3][1] = 'g';
  test[3][2] = 'b';
  test[3][3] = '\0';

after the initialization of the 2d array test, rownum no longer equals zero. The only other place I use rownum is a function readline() which looks like this.

Code:

char* readline(){
  return(test[rownum++]);
}

I have no clue why rownum is becoming altered because I never call readline()

What does rownum equal to when you try printing it?

Also, how is the test variable declared?

Would be nice to see all your code. If int rownum is trully getting altered they you have some sort of stack corruption occuring within your program. You will have to place some printf statements periodically throughout printing out the value of rownum from time to time to see what is occuring. Are you getting any compiler errors/warnings at all? It would be obvious of you are really hitting some memory boundaries though.

You should check that test is

Code:

test[4][5]

or larger.

oh it might be cause my test initializations we're declared out of range of my declaration of test. But would that affect other variables?

Absolutely! When you overrun the bounds of some variable, whatever you do will frequently impact some other variable.

It doesn't matter whether variables are on some stack or not. They could be globally defined. The issue is that the compiler allocates memory for each variable someplace. Likely consecutive areas. When an array is accessed beyond its logical limits, the areas outside of its bounds are affected. There is usually no run-time checking of array bounds. Arbitrary pointer values or indices can end up reading or writing to memory that's designated part of user's data area at least - hopefully. Best case. But it may impact more strategically significant parts of the computer as well causing major crashes.