stdio.h

int fgetc(FILE * stream){
	if(stdin == stream){
		//< implement input one character
		char c = HAL_UART_Receive();
		return c;
	}

	return EOF;
}

int fputc(int ch, FILE *f){
	if(stdout == stream){
		//< implement output one character
		HAL_UART_Transmit(ch);
		return ch;
	}else if(stderr == stream){
		HAL_UART_Transmit(ch);
		return ch;
	}

	return EOF;
}

int ferror(FILE * f){
	switch(f){
	case stdin:
		break;
	case stdout:
		break;
	case stderr:
		break;
	default:
		return EOF;
	}
}

assert.h

_ARMABI_NORETURN void abort(void){
	__disable_irq();
	while(1);
}

_ARMABI_NORETURN void __aeabi_assert(const char * exp, const char * file, int line){
	fprintf(stderr, "Assert `%s` fail in `%s:%d`\n", exp, file, line);
	abort();
}

time.h

_ARMABI time_t time(time_t * timer){
	//< return seconds from epoch
}

wchar.h

wint_t fgetwc(struct __FILE * stream);
wint_t fputwc(wchar_t ch, struct __FILE * stream);