.ino

#define BAUD 115200UL
#define BAUD_TOL 5

#include <util/setbaud.h>

FILE uart_output;

void uart_init(void) {
  UBRR0H = UBRRH_VALUE;
  UBRR0L = UBRRL_VALUE;

#if USE_2X
  UCSR0A |= (1 << U2X0);
#else
  UCSR0A &= ~(1 << U2X0);
#endif

  UCSR0C = (1 << UCSZ01) | (1 << UCSZ00); // 8-bit data
  UCSR0B = (1 <<  RXEN0) | (1 <<  TXEN0); // enable RX and TX
}

inline void uart_putchar(char c, FILE *) {
  loop_until_bit_is_set(UCSR0A, UDRE0);
  UDR0 = c;
}

void setup() {
  uart_init();
  fdev_setup_stream(&uart_output, uart_putchar, NULL, _FDEV_SETUP_WRITE);
  fprintf(&uart_output, "Hello, World!\r\n");
}

void loop() {

}

gistfile1.txt

Sketch uses 712 bytes (2%) of program storage space. Maximum is 32,256 bytes.
Global variables use 39 bytes (1%) of dynamic memory, leaving 2,009 bytes for local variables. Maximum is 2,048 bytes.