What was wrong with this code??

I suggest you use Quzah's suggestion for debugging. printf() is a lot easier to use than GDB.

Here is an example that might be a little more pertinant to you:

Code:

int a, c, b = 10;
char array[10];
for(a = 0; a <= b; a++) {
    c = array[a];
}

The above code will probably give you a seg fault. If you add in a printf() statement like so:

Code:

int a, c, b = 10;
char array[10];
for(a = 0; a <= b; a++) {
    printf("About to access index %d\n",a);
    c = array[a];
}

You will (hopefully) get the seg fault before it prints "About to access index 10". This helps you to realize that you are accessing the array outside its bounds.

Using quzah's example you're guaranteed that the debugging message will be shown because of the fflush() call.