Multidimensional array of uint16_t in C

Question

I want to write a method in C that gives me a multidimensional array of uint16_t.

I write this:

uint16_t ** GRAPHICS_CreateImage(int width, int height)
{
  int x;
  uint16_t **image = (uint16_t **)malloc(width * sizeof(uint16_t *));

  for(x=0; x < width; x++)
  {
      GUI_DUMY(x * 5, 0, 0x00F0);
      uint16_t *xx = (uint16_t *)malloc(height * sizeof(uint16_t));
      if(xx == NULL)
      {
        GUI_DUMY(0, 30, 0x0000);
      }
      GUI_DUMY(x * 5, 10, 0x000F);
      image[x] = xx;
      GUI_DUMY(x * 5, 20, 0xF000);
  }
  GUI_DUMY(0, 100, 0x0000);

  return image;
}

The program runs on an LCD-Display (I cannot debug code) and I need to do GUI_DUMY to see squares on the screen. So... my problem is that the malloc in the for hangs when x == 55. (I run the method with width 480 and height 320.)

When I have not enough memory, the malloc has to be finished and xx has to be NULL.

But xx is never NULL.

I have read, this problem can arise because of buffer overflow when mallocing, but I don't know if that is my problem?

Problem is certainly in other code. Post an [mcve]. Why check `xx ==NULL`, but not check `image == NULL`? — chux - Reinstate Monica, Dec 30 '19 at 00:03
Also, you [don't need to, and shouldn't, cast the result of `malloc`](https://stackoverflow.com/questions/605845/do-i-cast-the-result-of-malloc). — kopecs, Dec 30 '19 at 00:14
That's not a "multidimensional array". `image` is a pointer to an array of pointers to individual, separate one-dimensional arrays if `uint16_t` values. — Andrew Henle, Dec 30 '19 at 10:47
I can not post an minimal example because the Code runs on an LCD-Module. — 10110010, Dec 30 '19 at 13:28

score 0 · Answer 1 · answered Jan 04 '20 at 22:26

I am not sure what GUI_DUMY does nor how you intend to use the image array returned by this function, but here are some ideas to investigate:

you allocate an array of width pointers to arrays of height 16-bit words. You might need to swap these quantities.
you allocate an array of pointers to arrays, but the caller might expect an actual 2D array, ie an array of arrays, which is a very different type of object.

Multidimensional array of uint16_t in C

1 Answers1