c - fprintf() on avr-libc instantly crashes -

I am writing a program to run on an ATmega 328P - bare avr-libc Instead of Arduino though, it uses the Arduino bootloader on serial (though I do not think it affects the following question).

// if in the current LFS CRLF (C == '\ n') uart_putc ('\ r'); While (! (UCSR0A & amp; _BV (UDRE0)); UDR 0 = C; } Fixed int _putc (char c, FILE * _) {uart_putc (c); Return 0; } ... fdev_setup_stream (stdout, & amp; _putc, NULL, _FDEV_SETUP_WRITE);

If I now write my program using only fputc and fputs then all works fine i snprintf I can call () to enter a char buffer [16] and then in fputs () formatted stranders; All of these things work fine.

  fputs ("hello, world \ n", stdout); / * Works fine * / four buffer [16]; Snprintf (buffer, shape buffer, "hello,% s \ n", "world"); Breadth (buffer, standout); / * Also works fine * /   
 However, at this time I have to crash a real  fprintf ()  to  stdout  I try and reboot the atmega:  
  fprintf (stdout, "hello,% s \ n", "world");   
 Even before the initial  h  output, it immediately crashes.  
 Is there any such thing that might be missing,  snprintf ()  and  fputs ()  can work fine  < / Div>  
   Div class = "post-text" itemprop = "text"> 
 You can update the assignment of  stdout  For using  fdev_setup_stream () . Explains clearly:  
 
 Note: No work will be done in standard currents fdev_setup_stream () If standard currents are to be used, then this user needs to be allocated.   
 Indicates only one document. The code looks like yours except for two things:  
 
 
 A custom stream macro  FDEV_SETUP_STREAM () :    Fixed FILE Mystdout = FDEV_SETUP_STREAM (uart_putchar, NULL, _FDEV_SETUP_WRITE);    
 
  stdout  has been started in this custom stream:  
  stdout = & amp; Mystdout;     
 I think your code is using an unrestricted  stdout  stream "Introduction to standard IO features" (www .nongnu.org / avr-libc / user-manual / group__avr__stdio.html # details) says:  
 
 Standard studs stdin, stdout, and CDR are provided, but unlike the C standard , Since avr-libc has no information about the applicable device, so these streams are not already pre-initiated on the application startup.   
 All function calls using  stdout  are undefined where  stdout  relies on exactly what is pointing to it, Some calls may still work.