eXtremely strange problem with amount indicator

Look at this section of code:
Before calling this, the varible quads is 50.

Code:

---

  // Copy the wings to the other side now:
  for(x = 0, bWingsOut = FALSE; x < quads; x++) {
      if(quadEx[x] == XL_WING) bWingsOut = TRUE;
      if(bWingsOut) {
        if(quadEx[x] == XL_END) bWingsOut = FALSE;
        quadEx[quads] = quadEx[x]; // THIS LINE
        for(y = 0; y < 7; y++)
            quad[quads][y] = quad[x][y];
        quad[quads][1] = -quad[x][1];
        quads++;  }  }

---

After I call this, quads becomes 3. Why?? I only alter quads for the greater once!
The weird thing is, when I comment out THIS LINE, quads is what it's suppose to be.
Please help.

This is really strange; changing the code to

Code:

---

  // Copy the wings to the other side now:
  for(x = 0, bWingsOut = FALSE; x < quads; x++) {
      if(quadEx[x] == XL_WING) bWingsOut = TRUE;
      if(bWingsOut) {
        if(quadEx[x] == XL_END) bWingsOut = FALSE;
        if(quadEx[x] != XL_WING) quadEx[quads] = quadEx[x];
        else z = quads;
        for(y = 0; y < 7; y++)
            quad[quads][y] = quad[x][y];
        quad[quads][1] = -quad[x][1];
        quads++;  }  }
  quadEx[z] = XL_WING;

---

works.
If anyone knows why it's doing this I would still like to know!

Buffer overflow perhaps? Where is quadEx declared, and is its size at least 51?

Have you stepped through it to see it change there? I see no reason why the value of quads should change to 3....

Indeed. Have you tried printing quad's value for each iteration and seeing it change? Or does 'x<quads' only run once?

Is quad your own type? If so how do you pass into the [] operator? Reference? Do you change it?

This loop only runs once durring init.

I have already thought of buffer overflow, but as you can see my decs don't indicate anything of the sort.

Code:

---

#define XL_VECTOR  0
#define XL_END      1
#define XL_WING    2

#define MAX_QUADS 300
float quad[MAX_QUADS][7];
int quadEx[MAX_QUADS];
int quads, x, y, z;

---

EDIT:
The part that baffles me...
Like I pointed out in my 2nd post, the error only happens when I try to assign quadEx[quads] to the value 2.