Fixed heap array C for Stack ADT

stack-array.c

typedef struct flt_stack
{
  void** entries;
  int count;
  int capacity;
}flt_stack;

int flt_stack_create(flt_stack** s, int capacity)
{
  flt_stack* _s = (flt_stack*)flt_calloc(1,sizeof(flt_stack));
  if ( !_s ) return 0;  
  if (!capacity) 
    capacity = FLT_STACKARRAY_SIZE;

  _s->entries = (void**)flt_malloc(sizeof(void*)*capacity);
  if (!_s->entries) return  0;
  _s->capacity = capacity;

  *s = _s;
  return 1;
}

void flt_stack_destroy(flt_stack** s)
{
  if ( !s || !*s ) return;
  flt_safefree((*s)->entries);
  flt_safefree((*s));
}

void flt_stack_clear(flt_stack* s)
{
  s->count=0;
}

void flt_stack_push(flt_stack* s, void* value)
{
  if (s->count >= s->capacity )
  {
    FLT_BREAK;
    return;
  }
  s->entries[s->count++]=value;
}

void* flt_stack_top(flt_stack* s)
{
  return s->count ? s->entries[s->count-1] : fltnull;
}

void* flt_stack_pop(flt_stack* s)
{
  void* v=fltnull;

  if (s->count)
  {
    v=s->entries[--s->count];
  }
  return v;
}

int flt_stack_set_top_if_null(flt_stack* s, void* value)
{
  int r=0;
  if (s->count && !s->entries[s->count-1] )
  {
    s->entries[s->count-1]=value;
    r=1;
  }
  return r;
}