Setting an array pointer to null on declaration

Question

How can I set an array pointer to null?

I have a pointer to a 3 int array that I am trying to set to null.

int (*EXCLUSIVE_COLOR)[3];

Per this link I was trying to set it to null upon initialization.
However this does not assign a null value to it. It assigns three 'random' integers to the array elements:

{128, 447, 451}

How can I make it point to a null or empty value?

• Juraj: if you assign null, test it for null, not read it
• Delta_G: What were you expecting to get when you read a null pointer? That's undefined behavior. It could give you anything. If you want to make the thing pointed to zero then do that. That's not the same as assigning a null pointer.
• DataFiddler: Does this answer your question? Assigning an element of a multidimensional array to a second array

Answer 1

Here is a full example that shows you all thing things you have been asking over the past few days:

int colors[][3] = {
 {255, 0, 0},
 {0, 255, 0},
 {0, 0, 255}
};
#define NCOLOR (sizeof(colors) / sizeof(colors[0]))
int *EXCLUSIVE_COLOR = NULL;
void setup() {
 Serial.begin(115200);
 Serial.print("You have ");
 Serial.print(NCOLOR);
 Serial.println(" colors defined.");
 reportColor();
 EXCLUSIVE_COLOR = colors[2];
 reportColor();
 EXCLUSIVE_COLOR = NULL;
 reportColor();
}
void loop() {
}
void reportColor() {
 if (!EXCLUSIVE_COLOR) {
 Serial.println("Color is not set");
 } else {
 Serial.print("Color is set to ");
 Serial.print(EXCLUSIVE_COLOR[0]);
 Serial.print(",");
 Serial.print(EXCLUSIVE_COLOR[1]);
 Serial.print(",");
 Serial.println(EXCLUSIVE_COLOR[2]);
 }
}

You have an array of colours. You have a pointer that can point at a colour or at nothing. It starts off pointing at nothing. The code recognises that it's pointing at nothing and reports it. It gets assigned to a specific colour in your colours array. The code recognises that it's now a valid value and reports it. The pointer then gets pointed to nothing again. Again the code recognises that and tells you.

The result:

You have 3 colors defined.
Color is not set
Color is set to 0,0,255
Color is not set