I am trying to implement the simplest circular buffer in Arduino. I think I am able to implement it because my push and pop functions do not return any errors. However, when I want to print the data in the buffer using Serial.print(), the code goes into an infinite loop. Here is my code:

#include <stdio.h>

typedef struct circular_buffer
{
    int buffer_arr[5];
    int head;
    int tail;
} circular_buffer;

void setup()
{  
  Serial.begin(9600); 
  Serial.println("Circular buffer started");
}

void loop()
{  
  circular_buffer *cb;
  cb_init(cb);
  if(Serial.available()){
    char instruction = Serial.read();
    Serial.println(instruction);
    if(instruction == 'a'){
      if(Serial.available()){
        char instruction = Serial.read();
        Serial.println("here");
      }
      char key = Serial.read();
      cb_push_front(cb, key);
      Serial.print(String(key));
      Serial.println("    is entered");
    }
    else if(instruction == 'd'){
      cb_pop_back(cb);
      Serial.println("last item removed");
    }
//    for(int i=0; i<5; i++){
//      Serial.print(cb->buffer_arr[i]);
//      
//    }
    Serial.println("-");
  }
}



void cb_init(circular_buffer *cb)
{
    // cb->buffer_arr = {0,0,0,0,0};
    for(int i=0; i<5; i++){
      cb->buffer_arr[i] = 'c';
//      Serial.print(sizeof(*cb));
    }
//      Serial.print(cb->buffer_arr[0]);
    cb->head = 0;
    cb->tail = 0;
}


void cb_push_front(circular_buffer *cb, char item)
{
    cb->head++;
    cb->buffer_arr[cb->head] = item;
}

void cb_pop_back(circular_buffer *cb)
{
    cb->tail++;
    cb->buffer_arr[cb->tail] = 0;
}

The for loop which I commented out is the problematic one - or at least what I believe. My problem can be very much related to my poor C-language skills. I thought that cb->buffer_arr = {0,0,0,0,0}; code piece in the initialization function should have worked (thinking very much Python-ic way) but it didn't.

So, if anyone can see the issue and help me fixing it, I'd be very much appreciated. Thanks in advance.