In SDL_x11mouse.c file there is function named 
static Cursor
X11_CreatePixmapCursor(SDL_Surface * surface, int hot_x, int hot_y)
{
  // Some code

  data_bits = SDL_calloc(1, surface->h * width_bytes);
  mask_bits = SDL_calloc(1, surface->h * width_bytes);
  if (!data_bits || !mask_bits) {
     SDL_OutOfMemory();
     return None;
  }
 
 // Some code

}

Here is the problem in if statement,
suppose if !data_bits is false and !mask_bits is true then,
data_bits will go out of scope and leaks the memory it points to.

Solution is that data_bits and mask_bits should be checked separately, not by using OR operator.