c++ Mixing printf with wprintf (or cout with wcout)

I know you should not mix printing with printf,cout and wprintf,wcout, but have a hard time finding a good answer why and if it is possible to get round it. The problem is I use a external library that prints with printf and my own uses wcout. If I do a simple example it works fine, but from my full application it simply does not print the printf statements. If this is really a limitation, then there would be many libraries out there which can not work together with wide printing applications. Any insight on this is more than welcome. Update : I boiled it down to : ``` #include <stdio.h> #include <stdlib.h> #include <iostream> #include <readline/readline.h> #include <readline/history.h> int main() { char *buf; std::wcout << std::endl; /* ADDING THIS LINE MAKES PRINTF VANISH!!! */ rl_bind_key('\t',rl_abort);//disable auto-complete while((buf = readline("my-command : "))!=NULL) { if (strcmp(buf,"quit")==0) break; std::wcout<<buf<< std::endl; if (buf[0]!=0) add_history(buf); } free(buf); return 0; } ``` So I guess it might be a flushing problem, but it still looks strange to me, I have to check up on it. Update -> Work around : First of all, the same problem arise with wprintf. But I found that adding : ``` std::ios::sync_with_stdio(false); ``` actually did the trick...(note false and not as I would expect true..), the only thing that bothers me, is that I don't understand why and how to figure it out :-(