thank you so much for this terrific module! This issue is most likely not a problem with your code and perhaps a user question. You did not state if or how you would like to address these so I hope you do not mind that I put it in here.

I am using your library on a LPC1343 in a FreeRTOS context. I believe my FreeRTOS configuration works stable since I can ran tasks and queues for hours. I am working on a serial "CLI'". My xprintf also runs stable-ish. But once I use xformatc my application immediately hangs.

The test suite for xformatc has 70% code coverage so I am confident that I did not mess up your code base. Currently I do not feel very confident to debug the embedded FreeRTOS setting I have so I hope you would share some tips for trouble-shooting with me.

I should probably state that I run version 1.01 of your code.

the xprintf function I came up with:

#include <stdarg.h>
#include "xprintf.h"
#include "xformatc.h"
#include "uart.h"

static void put_char(void *arg, char c) {
  //UARTSendChar((uint8_t) c);
  UARTSendChar(c);
}

void xprintf(const char *fmt, ...) {
  va_list args;
  va_start(args, fmt);
  xvformat(put_char, NULL, fmt, args);
  va_end(args);
}

void xvprintf(const char *fmt, va_list _args) {
  //va_list args;
  //va_copy(args, _args);
  xvformat(put_char, NULL, fmt, _args);
  //va_end(args);
}

in xformatc.c around line 867, the long long type is popped off the stack, but on the CPU i'm compiling for (a PIC32MX, with the XC32 compiler) this doesn't work. instead it results in some out-of-boundary garbage.

so when changing the case statement to something like this, it does work:

case FLAG_TYPE_LONGLONG: {
	long high = (LONG)va_arg(args,long);
	long low = (LONG)va_arg(args,long);
	
	param.values.llvalue = (LONGLONG)high << 32 | low;
	break;
}

thought i'd let you know